[PATCH v9 0/6] MHDP8546 fixes related to DBANC usecase

[PATCH v9 0/6] MHDP8546 fixes related to DBANC usecase

[Harikrishna Shenoy]

With the DBANC framework, the connector is no longer initialized in 
bridge_attach() when the display controller sets the 
DRM_BRIDGE_ATTACH_NO_CONNECTOR flag. 
This causes a null pointer dereference in cdns_mhdp_modeset_retry_fn() 
when trying to access &conn->dev->mode_config.mutex. 
Observed on a board where EDID read failed. 
(log: https://gist.github.com/Jayesh2000/233f87f9becdf1e66f1da6fd53f77429)

Patch 1 adds a connector_ptr which takes care of both 
DBANC and !DBANC case by setting the pointer in appropriate hooks
and checking for pointer validity before accessing the connector.
Patch 2 adds mode validation hook to bridge fucntions.
Patch 3 fixes HDCP to work with both DBANC and !DBANC case by
moving HDCP state handling into the bridge atomic check in line with 
the DBANC model.
Patches 4,5 do necessary cleanup and alignment for using
connector pointer.

The rationale behind the sequence of commits is we can cleanly 
switch to drm_connector pointer after removal of connector helper 
code blocks, which are anyways not touch after DBANC has been 
enabled in driver.

The last patch make smaller adjustments: lowering the log level for
noisy DPCD transfer errors.

v8 patch link:
<https://lore.kernel.org/all/20251014094527.3916421-1-h-shenoy@ti.com/>

Changelog v8-v9:
-Move the patch 6 in v8 related to HDCP to patch 3 and add fixes tag.
-Update to connector_ptr in HDCP code in patch 1.
-Rebased on next-20251114.

v7 patch link:
<https://lore.kernel.org/all/20250929083936.1575685-1-h-shenoy@ti.com/>

Changelog v7-v8:
-Move patches with firxes tag to top of series with appropriate changes
to them.
-Add R/B tag to patch 
https://lore.kernel.org/all/ae3snoap64r252sbqhsshsadxfmlqdfn6b4o5fgfcmxppglkqf@2lsstfsghzwb/

v6 patch link:
<https://lore.kernel.org/all/20250909090824.1655537-1-h-shenoy@ti.com/>

Changelog v6-v7:
-Update cover letter to explain the series.
-Add R/B tag in PATCH 1 and drop fixes tag as suggested.
-Drop fixes tag in PATCH 2.
-Update the commit messages for clear understanding of changes done in patches.

v5 patch link:
<https://lore.kernel.org/all/20250811075904.1613519-1-h-shenoy@ti.com/>

Changelog v5 -> v6:
-Update cover letter to clarify the series in better way.
-Add Reviewed-by tag to relevant patches.
 
v4 patch link: 
<https://lore.kernel.org/all/20250624054448.192801-1-j-choudhary@ti.com>

Changelog v4->v5:
- Handle HDCP state in bridge atomic check instead of connector 
atomic check
 
v3 patch link:
<https://lore.kernel.org/all/20250529142517.188786-1-j-choudhary@ti.com/>

Changelog v3->v4:
- Fix kernel test robot build warning:
  <https://lore.kernel.org/all/202505300201.2s6r12yc-lkp@intel.com/>

v2 patch link:
<https://lore.kernel.org/all/20250521073237.366463-1-j-choudhary@ti.com/>

Changelog v2->v3:
- Add mode_valid in drm_bridge_funcs to a separate patch
- Remove "if (mhdp->connector.dev)" conditions that were missed in v2
- Split out the move of drm_atomic_get_new_connector_for_encoder()
  to a separate patch
- Drop "R-by" considering the changes in v2[1/3]
- Add Fixes tag to first 4 patches:
  commit c932ced6b585 ("drm/tidss: Update encoder/bridge chain connect model")
  This added DBANC flag in tidss while attaching bridge to the encoder
- Drop RFC prefix

v1 patch link:
<https://lore.kernel.org/all/20250116111636.157641-1-j-choudhary@ti.com/>

Changelog v1->v2:
- Remove !DRM_BRIDGE_ATTACH_NO_CONNECTOR entirely
- Add mode_valid in drm_bridge_funcs[0]
- Fix NULL POINTER differently since we cannot access atomic_state
- Reduce log level in cdns_mhdp_transfer call

[0]: https://lore.kernel.org/all/20240530091757.433106-1-j-choudhary@ti.com/

Harikrishna Shenoy (1):
  drm/bridge: cadence: cdns-mhdp8546-core: Handle HDCP state in bridge
    atomic check

Jayesh Choudhary (5):
  drm/bridge: cadence: cdns-mhdp8546-core: Set the mhdp connector
    earlier in atomic_enable()
  drm/bridge: cadence: cdns-mhdp8546-core: Add mode_valid hook to
    drm_bridge_funcs
  drm/bridge: cadence: cdns-mhdp8546-core: Remove legacy support for
    connector initialisation in bridge
  drm/bridge: cadence: cdns-mhdp8546*: Change drm_connector from
    structure to pointer
  drm/bridge: cadence: cdns-mhdp8546-core: Reduce log level for DPCD
    read/write

 .../drm/bridge/cadence/cdns-mhdp8546-core.c   | 258 +++++-------------
 .../drm/bridge/cadence/cdns-mhdp8546-core.h   |   2 +-
 .../drm/bridge/cadence/cdns-mhdp8546-hdcp.c   |   8 +-
 3 files changed, 72 insertions(+), 196 deletions(-)

-- 
2.34.1

[PATCH v9 1/6] drm/bridge: cadence: cdns-mhdp8546-core: Set the mhdp connector earlier in atomic_enable()

[Harikrishna Shenoy]

From: Jayesh Choudhary <j-choudhary@ti.com>

In case if we get errors in cdns_mhdp_link_up() or cdns_mhdp_reg_read()
in atomic_enable, we will go to cdns_mhdp_modeset_retry_fn() and will hit
NULL pointer while trying to access the mutex. We need the connector to
be set before that. Unlike in legacy !(DBANC) cases, we do not have
connector initialised in bridge_attach(), so add the mhdp->connector_ptr
in device structure to handle both DBANC and !DBANC case and set it in
atomic_enable() earlier to avoid possible NULL pointer dereference in
recovery paths like modeset_retry_fn() with the DBANC flag set.

Fixes: c932ced6b585 ("drm/tidss: Update encoder/bridge chain connect model")
Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
Signed-off-by: Harikrishna Shenoy <h-shenoy@ti.com>
---
 .../drm/bridge/cadence/cdns-mhdp8546-core.c   | 29 ++++++++++---------
 .../drm/bridge/cadence/cdns-mhdp8546-core.h   |  1 +
 .../drm/bridge/cadence/cdns-mhdp8546-hdcp.c   | 26 ++++++++++++-----
 3 files changed, 34 insertions(+), 22 deletions(-)

diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
index 38726ae1bf150..f3076e9cdabbe 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
@@ -740,7 +740,7 @@ static void cdns_mhdp_fw_cb(const struct firmware *fw, void *context)
 	bridge_attached = mhdp->bridge_attached;
 	spin_unlock(&mhdp->start_lock);
 	if (bridge_attached) {
-		if (mhdp->connector.dev)
+		if (mhdp->connector_ptr && mhdp->connector_ptr->dev)
 			drm_kms_helper_hotplug_event(mhdp->bridge.dev);
 		else
 			drm_bridge_hpd_notify(&mhdp->bridge, cdns_mhdp_detect(mhdp));
@@ -1636,6 +1636,7 @@ static int cdns_mhdp_connector_init(struct cdns_mhdp_device *mhdp)
 		return ret;
 	}
 
+	mhdp->connector_ptr = conn;
 	drm_connector_helper_add(conn, &cdns_mhdp_conn_helper_funcs);
 
 	ret = drm_display_info_set_bus_formats(&conn->display_info,
@@ -1915,17 +1916,25 @@ static void cdns_mhdp_atomic_enable(struct drm_bridge *bridge,
 	struct cdns_mhdp_device *mhdp = bridge_to_mhdp(bridge);
 	struct cdns_mhdp_bridge_state *mhdp_state;
 	struct drm_crtc_state *crtc_state;
-	struct drm_connector *connector;
 	struct drm_connector_state *conn_state;
 	struct drm_bridge_state *new_state;
 	const struct drm_display_mode *mode;
 	u32 resp;
-	int ret;
+	int ret = 0;
 
 	dev_dbg(mhdp->dev, "bridge enable\n");
 
 	mutex_lock(&mhdp->link_mutex);
 
+	mhdp->connector_ptr = drm_atomic_get_new_connector_for_encoder(state,
+								       bridge->encoder);
+	if (WARN_ON(!mhdp->connector_ptr))
+		goto out;
+
+	conn_state = drm_atomic_get_new_connector_state(state, mhdp->connector_ptr);
+	if (WARN_ON(!conn_state))
+		goto out;
+
 	if (mhdp->plugged && !mhdp->link_up) {
 		ret = cdns_mhdp_link_up(mhdp);
 		if (ret < 0)
@@ -1945,15 +1954,6 @@ static void cdns_mhdp_atomic_enable(struct drm_bridge *bridge,
 	cdns_mhdp_reg_write(mhdp, CDNS_DPTX_CAR,
 			    resp | CDNS_VIF_CLK_EN | CDNS_VIF_CLK_RSTN);
 
-	connector = drm_atomic_get_new_connector_for_encoder(state,
-							     bridge->encoder);
-	if (WARN_ON(!connector))
-		goto out;
-
-	conn_state = drm_atomic_get_new_connector_state(state, connector);
-	if (WARN_ON(!conn_state))
-		goto out;
-
 	if (mhdp->hdcp_supported &&
 	    mhdp->hw_state == MHDP_HW_READY &&
 	    conn_state->content_protection ==
@@ -2030,6 +2030,7 @@ static void cdns_mhdp_atomic_disable(struct drm_bridge *bridge,
 	if (mhdp->info && mhdp->info->ops && mhdp->info->ops->disable)
 		mhdp->info->ops->disable(mhdp);
 
+	mhdp->connector_ptr = NULL;
 	mutex_unlock(&mhdp->link_mutex);
 }
 
@@ -2296,7 +2297,7 @@ static void cdns_mhdp_modeset_retry_fn(struct work_struct *work)
 
 	mhdp = container_of(work, typeof(*mhdp), modeset_retry_work);
 
-	conn = &mhdp->connector;
+	conn = mhdp->connector_ptr;
 
 	/* Grab the locks before changing connector property */
 	mutex_lock(&conn->dev->mode_config.mutex);
@@ -2373,7 +2374,7 @@ static void cdns_mhdp_hpd_work(struct work_struct *work)
 	int ret;
 
 	ret = cdns_mhdp_update_link_status(mhdp);
-	if (mhdp->connector.dev) {
+	if (mhdp->connector_ptr && mhdp->connector_ptr->dev) {
 		if (ret < 0)
 			schedule_work(&mhdp->modeset_retry_work);
 		else
diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.h b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.h
index bad2fc0c73066..a76775c768956 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.h
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.h
@@ -376,6 +376,7 @@ struct cdns_mhdp_device {
 	struct mutex link_mutex;
 
 	struct drm_connector connector;
+	struct drm_connector *connector_ptr;
 	struct drm_bridge bridge;
 
 	struct cdns_mhdp_link link;
diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-hdcp.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-hdcp.c
index 42248f179b69d..5ac2fad2f0078 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-hdcp.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-hdcp.c
@@ -393,8 +393,10 @@ static int _cdns_mhdp_hdcp_disable(struct cdns_mhdp_device *mhdp)
 {
 	int ret;
 
-	dev_dbg(mhdp->dev, "[%s:%d] HDCP is being disabled...\n",
-		mhdp->connector.name, mhdp->connector.base.id);
+	if (mhdp->connector_ptr) {
+		dev_dbg(mhdp->dev, "[%s:%d] HDCP is being disabled...\n",
+			mhdp->connector_ptr->name, mhdp->connector_ptr->base.id);
+	}
 
 	ret = cdns_mhdp_hdcp_set_config(mhdp, 0, false);
 
@@ -443,9 +445,11 @@ static int cdns_mhdp_hdcp_check_link(struct cdns_mhdp_device *mhdp)
 	if (!ret && hdcp_port_status & HDCP_PORT_STS_AUTH)
 		goto out;
 
-	dev_err(mhdp->dev,
-		"[%s:%d] HDCP link failed, retrying authentication\n",
-		mhdp->connector.name, mhdp->connector.base.id);
+	if (mhdp->connector_ptr) {
+		dev_err(mhdp->dev,
+			"[%s:%d] HDCP link failed, retrying authentication\n",
+			mhdp->connector_ptr->name, mhdp->connector_ptr->base.id);
+	}
 
 	ret = _cdns_mhdp_hdcp_disable(mhdp);
 	if (ret) {
@@ -487,13 +491,19 @@ static void cdns_mhdp_hdcp_prop_work(struct work_struct *work)
 	struct cdns_mhdp_device *mhdp = container_of(hdcp,
 						     struct cdns_mhdp_device,
 						     hdcp);
-	struct drm_device *dev = mhdp->connector.dev;
+	struct drm_device *dev = NULL;
 	struct drm_connector_state *state;
 
+	if (mhdp->connector_ptr)
+		dev = mhdp->connector_ptr->dev;
+
+	if (!dev)
+		return;
+
 	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
 	mutex_lock(&mhdp->hdcp.mutex);
-	if (mhdp->hdcp.value != DRM_MODE_CONTENT_PROTECTION_UNDESIRED) {
-		state = mhdp->connector.state;
+	if (mhdp->connector_ptr && mhdp->hdcp.value != DRM_MODE_CONTENT_PROTECTION_UNDESIRED) {
+		state = mhdp->connector_ptr->state;
 		state->content_protection = mhdp->hdcp.value;
 	}
 	mutex_unlock(&mhdp->hdcp.mutex);
-- 
2.34.1

[PATCH v9 2/6] drm/bridge: cadence: cdns-mhdp8546-core: Add mode_valid hook to drm_bridge_funcs

[Harikrishna Shenoy]

From: Jayesh Choudhary <j-choudhary@ti.com>

Add cdns_mhdp_bridge_mode_valid() to check if specific mode is valid for
this bridge or not. In the legacy !(DBANC) usecase, we were using the hook
from drm_connector_helper_funcs but with DBANC we need to have mode_valid()
in drm_bridge_funcs.

Fixes: c932ced6b585 ("drm/tidss: Update encoder/bridge chain connect model")
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
Signed-off-by: Harikrishna Shenoy <h-shenoy@ti.com>
---
 .../drm/bridge/cadence/cdns-mhdp8546-core.c   | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
index f3076e9cdabbe..7178a01e4d4d8 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
@@ -2162,6 +2162,25 @@ static const struct drm_edid *cdns_mhdp_bridge_edid_read(struct drm_bridge *brid
 	return cdns_mhdp_edid_read(mhdp, connector);
 }
 
+static enum drm_mode_status
+cdns_mhdp_bridge_mode_valid(struct drm_bridge *bridge,
+			    const struct drm_display_info *info,
+			    const struct drm_display_mode *mode)
+{
+	struct cdns_mhdp_device *mhdp = bridge_to_mhdp(bridge);
+
+	mutex_lock(&mhdp->link_mutex);
+
+	if (!cdns_mhdp_bandwidth_ok(mhdp, mode, mhdp->link.num_lanes,
+				    mhdp->link.rate)) {
+		mutex_unlock(&mhdp->link_mutex);
+		return MODE_CLOCK_HIGH;
+	}
+
+	mutex_unlock(&mhdp->link_mutex);
+	return MODE_OK;
+}
+
 static const struct drm_bridge_funcs cdns_mhdp_bridge_funcs = {
 	.atomic_enable = cdns_mhdp_atomic_enable,
 	.atomic_disable = cdns_mhdp_atomic_disable,
@@ -2176,6 +2195,7 @@ static const struct drm_bridge_funcs cdns_mhdp_bridge_funcs = {
 	.edid_read = cdns_mhdp_bridge_edid_read,
 	.hpd_enable = cdns_mhdp_bridge_hpd_enable,
 	.hpd_disable = cdns_mhdp_bridge_hpd_disable,
+	.mode_valid = cdns_mhdp_bridge_mode_valid,
 };
 
 static bool cdns_mhdp_detect_hpd(struct cdns_mhdp_device *mhdp, bool *hpd_pulse)
-- 
2.34.1

[PATCH v9 3/6] drm/bridge: cadence: cdns-mhdp8546-core: Handle HDCP state in bridge atomic check

[Harikrishna Shenoy]

Now that we have DBANC framework, handle the HDCP state change in 
bridge atomic check as well to enable correct functioning for HDCP in 
DBANC and !DBANC case.

Fixes: 6a3608eae6d33 ("drm: bridge: cdns-mhdp8546: Enable HDCP")
Signed-off-by: Harikrishna Shenoy <h-shenoy@ti.com>
---
 .../drm/bridge/cadence/cdns-mhdp8546-core.c   | 23 +++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
index 7178a01e4d4d8..d944095da4722 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
@@ -2123,6 +2123,10 @@ static int cdns_mhdp_atomic_check(struct drm_bridge *bridge,
 {
 	struct cdns_mhdp_device *mhdp = bridge_to_mhdp(bridge);
 	const struct drm_display_mode *mode = &crtc_state->adjusted_mode;
+	struct drm_connector_state *old_state, *new_state;
+	struct drm_atomic_state *state = crtc_state->state;
+	struct drm_connector *conn = mhdp->connector_ptr;
+	u64 old_cp, new_cp;
 
 	mutex_lock(&mhdp->link_mutex);
 
@@ -2142,6 +2146,25 @@ static int cdns_mhdp_atomic_check(struct drm_bridge *bridge,
 	if (mhdp->info)
 		bridge_state->input_bus_cfg.flags = *mhdp->info->input_bus_flags;
 
+	if (conn && mhdp->hdcp_supported) {
+		old_state = drm_atomic_get_old_connector_state(state, conn);
+		new_state = drm_atomic_get_new_connector_state(state, conn);
+		old_cp = old_state->content_protection;
+		new_cp = new_state->content_protection;
+
+		if (old_state->hdcp_content_type != new_state->hdcp_content_type &&
+		    new_cp != DRM_MODE_CONTENT_PROTECTION_UNDESIRED) {
+			new_state->content_protection = DRM_MODE_CONTENT_PROTECTION_DESIRED;
+			crtc_state = drm_atomic_get_new_crtc_state(state, new_state->crtc);
+			crtc_state->mode_changed = true;
+		}
+
+		if (!new_state->crtc) {
+			if (old_cp == DRM_MODE_CONTENT_PROTECTION_ENABLED)
+				new_state->content_protection = DRM_MODE_CONTENT_PROTECTION_DESIRED;
+		}
+	}
+
 	mutex_unlock(&mhdp->link_mutex);
 	return 0;
 }
-- 
2.34.1

[PATCH v9 4/6] drm/bridge: cadence: cdns-mhdp8546-core: Remove legacy support for connector initialisation in bridge

[Harikrishna Shenoy]

From: Jayesh Choudhary <j-choudhary@ti.com>

Now that we have DBANC framework, remove the connector initialisation code
as that piece of code is not called if DRM_BRIDGE_ATTACH_NO_CONNECTOR flag
is used. Only TI K3 platforms consume this driver and tidss (their display
controller) has this flag set. So this legacy support can be dropped.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
Signed-off-by: Harikrishna Shenoy <h-shenoy@ti.com>
---
 .../drm/bridge/cadence/cdns-mhdp8546-core.c   | 188 +-----------------
 1 file changed, 10 insertions(+), 178 deletions(-)

diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
index d944095da4722..816d5d87b45fe 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
@@ -739,12 +739,8 @@ static void cdns_mhdp_fw_cb(const struct firmware *fw, void *context)
 	spin_lock(&mhdp->start_lock);
 	bridge_attached = mhdp->bridge_attached;
 	spin_unlock(&mhdp->start_lock);
-	if (bridge_attached) {
-		if (mhdp->connector_ptr && mhdp->connector_ptr->dev)
-			drm_kms_helper_hotplug_event(mhdp->bridge.dev);
-		else
-			drm_bridge_hpd_notify(&mhdp->bridge, cdns_mhdp_detect(mhdp));
-	}
+	if (bridge_attached)
+		drm_bridge_hpd_notify(&mhdp->bridge, cdns_mhdp_detect(mhdp));
 }
 
 static int cdns_mhdp_load_firmware(struct cdns_mhdp_device *mhdp)
@@ -1444,56 +1440,6 @@ static const struct drm_edid *cdns_mhdp_edid_read(struct cdns_mhdp_device *mhdp,
 	return drm_edid_read_custom(connector, cdns_mhdp_get_edid_block, mhdp);
 }
 
-static int cdns_mhdp_get_modes(struct drm_connector *connector)
-{
-	struct cdns_mhdp_device *mhdp = connector_to_mhdp(connector);
-	const struct drm_edid *drm_edid;
-	int num_modes;
-
-	if (!mhdp->plugged)
-		return 0;
-
-	drm_edid = cdns_mhdp_edid_read(mhdp, connector);
-
-	drm_edid_connector_update(connector, drm_edid);
-
-	if (!drm_edid) {
-		dev_err(mhdp->dev, "Failed to read EDID\n");
-		return 0;
-	}
-
-	num_modes = drm_edid_connector_add_modes(connector);
-	drm_edid_free(drm_edid);
-
-	/*
-	 * HACK: Warn about unsupported display formats until we deal
-	 *       with them correctly.
-	 */
-	if (connector->display_info.color_formats &&
-	    !(connector->display_info.color_formats &
-	      mhdp->display_fmt.color_format))
-		dev_warn(mhdp->dev,
-			 "%s: No supported color_format found (0x%08x)\n",
-			__func__, connector->display_info.color_formats);
-
-	if (connector->display_info.bpc &&
-	    connector->display_info.bpc < mhdp->display_fmt.bpc)
-		dev_warn(mhdp->dev, "%s: Display bpc only %d < %d\n",
-			 __func__, connector->display_info.bpc,
-			 mhdp->display_fmt.bpc);
-
-	return num_modes;
-}
-
-static int cdns_mhdp_connector_detect(struct drm_connector *conn,
-				      struct drm_modeset_acquire_ctx *ctx,
-				      bool force)
-{
-	struct cdns_mhdp_device *mhdp = connector_to_mhdp(conn);
-
-	return cdns_mhdp_detect(mhdp);
-}
-
 static u32 cdns_mhdp_get_bpp(struct cdns_mhdp_display_fmt *fmt)
 {
 	u32 bpp;
@@ -1547,115 +1493,6 @@ bool cdns_mhdp_bandwidth_ok(struct cdns_mhdp_device *mhdp,
 	return true;
 }
 
-static
-enum drm_mode_status cdns_mhdp_mode_valid(struct drm_connector *conn,
-					  const struct drm_display_mode *mode)
-{
-	struct cdns_mhdp_device *mhdp = connector_to_mhdp(conn);
-
-	mutex_lock(&mhdp->link_mutex);
-
-	if (!cdns_mhdp_bandwidth_ok(mhdp, mode, mhdp->link.num_lanes,
-				    mhdp->link.rate)) {
-		mutex_unlock(&mhdp->link_mutex);
-		return MODE_CLOCK_HIGH;
-	}
-
-	mutex_unlock(&mhdp->link_mutex);
-	return MODE_OK;
-}
-
-static int cdns_mhdp_connector_atomic_check(struct drm_connector *conn,
-					    struct drm_atomic_state *state)
-{
-	struct cdns_mhdp_device *mhdp = connector_to_mhdp(conn);
-	struct drm_connector_state *old_state, *new_state;
-	struct drm_crtc_state *crtc_state;
-	u64 old_cp, new_cp;
-
-	if (!mhdp->hdcp_supported)
-		return 0;
-
-	old_state = drm_atomic_get_old_connector_state(state, conn);
-	new_state = drm_atomic_get_new_connector_state(state, conn);
-	old_cp = old_state->content_protection;
-	new_cp = new_state->content_protection;
-
-	if (old_state->hdcp_content_type != new_state->hdcp_content_type &&
-	    new_cp != DRM_MODE_CONTENT_PROTECTION_UNDESIRED) {
-		new_state->content_protection = DRM_MODE_CONTENT_PROTECTION_DESIRED;
-		goto mode_changed;
-	}
-
-	if (!new_state->crtc) {
-		if (old_cp == DRM_MODE_CONTENT_PROTECTION_ENABLED)
-			new_state->content_protection = DRM_MODE_CONTENT_PROTECTION_DESIRED;
-		return 0;
-	}
-
-	if (old_cp == new_cp ||
-	    (old_cp == DRM_MODE_CONTENT_PROTECTION_DESIRED &&
-	     new_cp == DRM_MODE_CONTENT_PROTECTION_ENABLED))
-		return 0;
-
-mode_changed:
-	crtc_state = drm_atomic_get_new_crtc_state(state, new_state->crtc);
-	crtc_state->mode_changed = true;
-
-	return 0;
-}
-
-static const struct drm_connector_helper_funcs cdns_mhdp_conn_helper_funcs = {
-	.detect_ctx = cdns_mhdp_connector_detect,
-	.get_modes = cdns_mhdp_get_modes,
-	.mode_valid = cdns_mhdp_mode_valid,
-	.atomic_check = cdns_mhdp_connector_atomic_check,
-};
-
-static const struct drm_connector_funcs cdns_mhdp_conn_funcs = {
-	.fill_modes = drm_helper_probe_single_connector_modes,
-	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
-	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
-	.reset = drm_atomic_helper_connector_reset,
-	.destroy = drm_connector_cleanup,
-};
-
-static int cdns_mhdp_connector_init(struct cdns_mhdp_device *mhdp)
-{
-	u32 bus_format = MEDIA_BUS_FMT_RGB121212_1X36;
-	struct drm_connector *conn = &mhdp->connector;
-	struct drm_bridge *bridge = &mhdp->bridge;
-	int ret;
-
-	conn->polled = DRM_CONNECTOR_POLL_HPD;
-
-	ret = drm_connector_init(bridge->dev, conn, &cdns_mhdp_conn_funcs,
-				 DRM_MODE_CONNECTOR_DisplayPort);
-	if (ret) {
-		dev_err(mhdp->dev, "Failed to initialize connector with drm\n");
-		return ret;
-	}
-
-	mhdp->connector_ptr = conn;
-	drm_connector_helper_add(conn, &cdns_mhdp_conn_helper_funcs);
-
-	ret = drm_display_info_set_bus_formats(&conn->display_info,
-					       &bus_format, 1);
-	if (ret)
-		return ret;
-
-	ret = drm_connector_attach_encoder(conn, bridge->encoder);
-	if (ret) {
-		dev_err(mhdp->dev, "Failed to attach connector to encoder\n");
-		return ret;
-	}
-
-	if (mhdp->hdcp_supported)
-		ret = drm_connector_attach_content_protection_property(conn, true);
-
-	return ret;
-}
-
 static int cdns_mhdp_attach(struct drm_bridge *bridge,
 			    struct drm_encoder *encoder,
 			    enum drm_bridge_attach_flags flags)
@@ -1672,9 +1509,11 @@ static int cdns_mhdp_attach(struct drm_bridge *bridge,
 		return ret;
 
 	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)) {
-		ret = cdns_mhdp_connector_init(mhdp);
-		if (ret)
-			goto aux_unregister;
+		ret = -EINVAL;
+		dev_err(mhdp->dev,
+			"Connector initialisation not supported in bridge_attach %d\n",
+			ret);
+		goto aux_unregister;
 	}
 
 	spin_lock(&mhdp->start_lock);
@@ -2414,17 +2253,10 @@ static void cdns_mhdp_hpd_work(struct work_struct *work)
 	struct cdns_mhdp_device *mhdp = container_of(work,
 						     struct cdns_mhdp_device,
 						     hpd_work);
-	int ret;
 
-	ret = cdns_mhdp_update_link_status(mhdp);
-	if (mhdp->connector_ptr && mhdp->connector_ptr->dev) {
-		if (ret < 0)
-			schedule_work(&mhdp->modeset_retry_work);
-		else
-			drm_kms_helper_hotplug_event(mhdp->bridge.dev);
-	} else {
-		drm_bridge_hpd_notify(&mhdp->bridge, cdns_mhdp_detect(mhdp));
-	}
+	cdns_mhdp_update_link_status(mhdp);
+
+	drm_bridge_hpd_notify(&mhdp->bridge, cdns_mhdp_detect(mhdp));
 }
 
 static int cdns_mhdp_probe(struct platform_device *pdev)
-- 
2.34.1

[PATCH v9 5/6] cadence: cdns-mhdp8546*: Change drm_connector from structure to pointer

[Harikrishna Shenoy]

After adding DBANC framework, mhdp->connector is not initialised during
bridge_attach(). The connector is however required in few driver calls
like cdns_mhdp_hdcp_enable() and cdns_mhdp_modeset_retry_fn().
Now that we have dropped the legacy code which became redundant
with introduction of DBNAC usecase in driver, we can cleanly switch
to drm_connector pointer instead of structure.

Set it in bridge_enable() and clear it in bridge_disable(),
and make appropriate changes.

This allows us to dynamically set the reference in bridge_enable() when
the connector becomes available and clear it in bridge_disable().
This change is necessary to properly integrate with the DBANC framework
while maintaining all connector-dependent functionality in the driver.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
Signed-off-by: Harikrishna Shenoy <h-shenoy@ti.com>
---
 .../gpu/drm/bridge/cadence/cdns-mhdp8546-core.c  | 14 +++++++-------
 .../gpu/drm/bridge/cadence/cdns-mhdp8546-core.h  |  3 +--
 .../gpu/drm/bridge/cadence/cdns-mhdp8546-hdcp.c  | 16 ++++++++--------
 3 files changed, 16 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
index 816d5d87b45fe..002b4be3de674 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
@@ -1765,12 +1765,12 @@ static void cdns_mhdp_atomic_enable(struct drm_bridge *bridge,
 
 	mutex_lock(&mhdp->link_mutex);
 
-	mhdp->connector_ptr = drm_atomic_get_new_connector_for_encoder(state,
-								       bridge->encoder);
-	if (WARN_ON(!mhdp->connector_ptr))
+	mhdp->connector = drm_atomic_get_new_connector_for_encoder(state,
+								   bridge->encoder);
+	if (WARN_ON(!mhdp->connector))
 		goto out;
 
-	conn_state = drm_atomic_get_new_connector_state(state, mhdp->connector_ptr);
+	conn_state = drm_atomic_get_new_connector_state(state, mhdp->connector);
 	if (WARN_ON(!conn_state))
 		goto out;
 
@@ -1869,7 +1869,7 @@ static void cdns_mhdp_atomic_disable(struct drm_bridge *bridge,
 	if (mhdp->info && mhdp->info->ops && mhdp->info->ops->disable)
 		mhdp->info->ops->disable(mhdp);
 
-	mhdp->connector_ptr = NULL;
+	mhdp->connector = NULL;
 	mutex_unlock(&mhdp->link_mutex);
 }
 
@@ -1964,7 +1964,7 @@ static int cdns_mhdp_atomic_check(struct drm_bridge *bridge,
 	const struct drm_display_mode *mode = &crtc_state->adjusted_mode;
 	struct drm_connector_state *old_state, *new_state;
 	struct drm_atomic_state *state = crtc_state->state;
-	struct drm_connector *conn = mhdp->connector_ptr;
+	struct drm_connector *conn = mhdp->connector;
 	u64 old_cp, new_cp;
 
 	mutex_lock(&mhdp->link_mutex);
@@ -2179,7 +2179,7 @@ static void cdns_mhdp_modeset_retry_fn(struct work_struct *work)
 
 	mhdp = container_of(work, typeof(*mhdp), modeset_retry_work);
 
-	conn = mhdp->connector_ptr;
+	conn = mhdp->connector;
 
 	/* Grab the locks before changing connector property */
 	mutex_lock(&conn->dev->mode_config.mutex);
diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.h b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.h
index a76775c768956..b297db53ba283 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.h
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.h
@@ -375,8 +375,7 @@ struct cdns_mhdp_device {
 	 */
 	struct mutex link_mutex;
 
-	struct drm_connector connector;
-	struct drm_connector *connector_ptr;
+	struct drm_connector *connector;
 	struct drm_bridge bridge;
 
 	struct cdns_mhdp_link link;
diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-hdcp.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-hdcp.c
index 5ac2fad2f0078..1d433ad3fe878 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-hdcp.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-hdcp.c
@@ -393,9 +393,9 @@ static int _cdns_mhdp_hdcp_disable(struct cdns_mhdp_device *mhdp)
 {
 	int ret;
 
-	if (mhdp->connector_ptr) {
+	if (mhdp->connector) {
 		dev_dbg(mhdp->dev, "[%s:%d] HDCP is being disabled...\n",
-			mhdp->connector_ptr->name, mhdp->connector_ptr->base.id);
+			mhdp->connector->name, mhdp->connector->base.id);
 	}
 
 	ret = cdns_mhdp_hdcp_set_config(mhdp, 0, false);
@@ -445,10 +445,10 @@ static int cdns_mhdp_hdcp_check_link(struct cdns_mhdp_device *mhdp)
 	if (!ret && hdcp_port_status & HDCP_PORT_STS_AUTH)
 		goto out;
 
-	if (mhdp->connector_ptr) {
+	if (mhdp->connector) {
 		dev_err(mhdp->dev,
 			"[%s:%d] HDCP link failed, retrying authentication\n",
-			mhdp->connector_ptr->name, mhdp->connector_ptr->base.id);
+			mhdp->connector->name, mhdp->connector->base.id);
 	}
 
 	ret = _cdns_mhdp_hdcp_disable(mhdp);
@@ -494,16 +494,16 @@ static void cdns_mhdp_hdcp_prop_work(struct work_struct *work)
 	struct drm_device *dev = NULL;
 	struct drm_connector_state *state;
 
-	if (mhdp->connector_ptr)
-		dev = mhdp->connector_ptr->dev;
+	if (mhdp->connector)
+		dev = mhdp->connector->dev;
 
 	if (!dev)
 		return;
 
 	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
 	mutex_lock(&mhdp->hdcp.mutex);
-	if (mhdp->connector_ptr && mhdp->hdcp.value != DRM_MODE_CONTENT_PROTECTION_UNDESIRED) {
-		state = mhdp->connector_ptr->state;
+	if (mhdp->connector && mhdp->hdcp.value != DRM_MODE_CONTENT_PROTECTION_UNDESIRED) {
+		state = mhdp->connector->state;
 		state->content_protection = mhdp->hdcp.value;
 	}
 	mutex_unlock(&mhdp->hdcp.mutex);
-- 
2.34.1

[PATCH v9 6/6] drm/bridge: cadence: cdns-mhdp8546-core: Reduce log level for DPCD read/write

[Harikrishna Shenoy]

From: Jayesh Choudhary <j-choudhary@ti.com>

Reduce the log level for cdns_mhdp_dpcd_read and cdns_mhdp_dpcd_write
errors in cdns_mhdp_transfer function as in case of failure, there is
flooding of these prints along with other indicators like EDID failure
logs which are fairly intuitive in themselves rendering these error logs
useless.
Also, the caller functions for the cdns_mhdp_transfer in drm_dp_helper.c
(which calls it 32 times), has debug log level in case transfer fails.
So having a superseding log level in cdns_mhdp_transfer seems bad.

Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
Signed-off-by: Harikrishna Shenoy <h-shenoy@ti.com>
---
 drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
index 002b4be3de674..120eb7ffe20c0 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
@@ -778,7 +778,7 @@ static ssize_t cdns_mhdp_transfer(struct drm_dp_aux *aux,
 			if (!ret)
 				continue;
 
-			dev_err(mhdp->dev,
+			dev_dbg(mhdp->dev,
 				"Failed to write DPCD addr %u\n",
 				msg->address + i);
 
@@ -788,7 +788,7 @@ static ssize_t cdns_mhdp_transfer(struct drm_dp_aux *aux,
 		ret = cdns_mhdp_dpcd_read(mhdp, msg->address,
 					  msg->buffer, msg->size);
 		if (ret) {
-			dev_err(mhdp->dev,
+			dev_dbg(mhdp->dev,
 				"Failed to read DPCD addr %u\n",
 				msg->address);
 
-- 
2.34.1

Re: [PATCH v9 0/6] MHDP8546 fixes related to DBANC usecase

[Maxime Ripard]

[-- Attachment #1: Type: text/plain, Size: 1242 bytes --]

Hi,

On Tue, Nov 18, 2025 at 05:22:49PM +0530, Harikrishna Shenoy wrote:
> With the DBANC framework, the connector is no longer initialized in 
> bridge_attach() when the display controller sets the 
> DRM_BRIDGE_ATTACH_NO_CONNECTOR flag. 
> This causes a null pointer dereference in cdns_mhdp_modeset_retry_fn() 
> when trying to access &conn->dev->mode_config.mutex. 
> Observed on a board where EDID read failed. 
> (log: https://gist.github.com/Jayesh2000/233f87f9becdf1e66f1da6fd53f77429)
> 
> Patch 1 adds a connector_ptr which takes care of both 
> DBANC and !DBANC case by setting the pointer in appropriate hooks
> and checking for pointer validity before accessing the connector.
> Patch 2 adds mode validation hook to bridge fucntions.
> Patch 3 fixes HDCP to work with both DBANC and !DBANC case by
> moving HDCP state handling into the bridge atomic check in line with 
> the DBANC model.
> Patches 4,5 do necessary cleanup and alignment for using
> connector pointer.

It's mentioned several times in your series, and it might be obvious to
you, but documenting what is the "DBANC framework" is would be helpful.
I have no idea what it's about, and it appears that Google doesn't know
either.

Maxime

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Re: [PATCH v9 0/6] MHDP8546 fixes related to DBANC usecase

[Tomi Valkeinen]

Hi,

On 18/11/2025 14:40, Maxime Ripard wrote:
> Hi,
> 
> On Tue, Nov 18, 2025 at 05:22:49PM +0530, Harikrishna Shenoy wrote:
>> With the DBANC framework, the connector is no longer initialized in 
>> bridge_attach() when the display controller sets the 
>> DRM_BRIDGE_ATTACH_NO_CONNECTOR flag. 
>> This causes a null pointer dereference in cdns_mhdp_modeset_retry_fn() 
>> when trying to access &conn->dev->mode_config.mutex. 
>> Observed on a board where EDID read failed. 
>> (log: https://gist.github.com/Jayesh2000/233f87f9becdf1e66f1da6fd53f77429)
>>
>> Patch 1 adds a connector_ptr which takes care of both 
>> DBANC and !DBANC case by setting the pointer in appropriate hooks
>> and checking for pointer validity before accessing the connector.
>> Patch 2 adds mode validation hook to bridge fucntions.
>> Patch 3 fixes HDCP to work with both DBANC and !DBANC case by
>> moving HDCP state handling into the bridge atomic check in line with 
>> the DBANC model.
>> Patches 4,5 do necessary cleanup and alignment for using
>> connector pointer.
> 
> It's mentioned several times in your series, and it might be obvious to
> you, but documenting what is the "DBANC framework" is would be helpful.
> I have no idea what it's about, and it appears that Google doesn't know
> either.
Yes, I was a bit baffled initially. DRM_BRIDGE_ATTACH_NO_CONNECTOR.

I think it makes sense to only use "DBANC" if it's first introduced in
that patch. So don't have a patch that just uses "DBANC", even if the
previous patch did explain what it means. And if there's just one or two
"DBANC"s, just spell it out "DRM_BRIDGE_ATTACH_NO_CONNECTOR".

 Tomi

Re: [PATCH v9 0/6] MHDP8546 fixes related to DBANC usecase

[Maxime Ripard]

[-- Attachment #1: Type: text/plain, Size: 1954 bytes --]

On Tue, Nov 18, 2025 at 04:52:49PM +0200, Tomi Valkeinen wrote:
> Hi,
> 
> On 18/11/2025 14:40, Maxime Ripard wrote:
> > Hi,
> > 
> > On Tue, Nov 18, 2025 at 05:22:49PM +0530, Harikrishna Shenoy wrote:
> >> With the DBANC framework, the connector is no longer initialized in 
> >> bridge_attach() when the display controller sets the 
> >> DRM_BRIDGE_ATTACH_NO_CONNECTOR flag. 
> >> This causes a null pointer dereference in cdns_mhdp_modeset_retry_fn() 
> >> when trying to access &conn->dev->mode_config.mutex. 
> >> Observed on a board where EDID read failed. 
> >> (log: https://gist.github.com/Jayesh2000/233f87f9becdf1e66f1da6fd53f77429)
> >>
> >> Patch 1 adds a connector_ptr which takes care of both 
> >> DBANC and !DBANC case by setting the pointer in appropriate hooks
> >> and checking for pointer validity before accessing the connector.
> >> Patch 2 adds mode validation hook to bridge fucntions.
> >> Patch 3 fixes HDCP to work with both DBANC and !DBANC case by
> >> moving HDCP state handling into the bridge atomic check in line with 
> >> the DBANC model.
> >> Patches 4,5 do necessary cleanup and alignment for using
> >> connector pointer.
> > 
> > It's mentioned several times in your series, and it might be obvious to
> > you, but documenting what is the "DBANC framework" is would be helpful.
> > I have no idea what it's about, and it appears that Google doesn't know
> > either.
> Yes, I was a bit baffled initially. DRM_BRIDGE_ATTACH_NO_CONNECTOR.

Oooooh, thanks

> I think it makes sense to only use "DBANC" if it's first introduced in
> that patch. So don't have a patch that just uses "DBANC", even if the
> previous patch did explain what it means. And if there's just one or two
> "DBANC"s, just spell it out "DRM_BRIDGE_ATTACH_NO_CONNECTOR".

Yeah, I'd go even further. Acronyms are fun but something being obvious
is better still. Use the proper flag name every time.

Maxime

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Re: [PATCH v9 0/6] MHDP8546 fixes related to DBANC usecase

[Harikrishna shenoy]

On 18/11/25 21:50, Maxime Ripard wrote:
> On Tue, Nov 18, 2025 at 04:52:49PM +0200, Tomi Valkeinen wrote:
>> Hi,
>>
>> On 18/11/2025 14:40, Maxime Ripard wrote:
>>> Hi,
>>>
>>> On Tue, Nov 18, 2025 at 05:22:49PM +0530, Harikrishna Shenoy wrote:
>>>> With the DBANC framework, the connector is no longer initialized in
>>>> bridge_attach() when the display controller sets the
>>>> DRM_BRIDGE_ATTACH_NO_CONNECTOR flag.
>>>> This causes a null pointer dereference in cdns_mhdp_modeset_retry_fn()
>>>> when trying to access &conn->dev->mode_config.mutex.
>>>> Observed on a board where EDID read failed.
>>>> (log: https://gist.github.com/Jayesh2000/233f87f9becdf1e66f1da6fd53f77429)
>>>>
>>>> Patch 1 adds a connector_ptr which takes care of both
>>>> DBANC and !DBANC case by setting the pointer in appropriate hooks
>>>> and checking for pointer validity before accessing the connector.
>>>> Patch 2 adds mode validation hook to bridge fucntions.
>>>> Patch 3 fixes HDCP to work with both DBANC and !DBANC case by
>>>> moving HDCP state handling into the bridge atomic check in line with
>>>> the DBANC model.
>>>> Patches 4,5 do necessary cleanup and alignment for using
>>>> connector pointer.
>>>
>>> It's mentioned several times in your series, and it might be obvious to
>>> you, but documenting what is the "DBANC framework" is would be helpful.
>>> I have no idea what it's about, and it appears that Google doesn't know
>>> either.
>> Yes, I was a bit baffled initially. DRM_BRIDGE_ATTACH_NO_CONNECTOR.
> 
> Oooooh, thanks
> 
>> I think it makes sense to only use "DBANC" if it's first introduced in
>> that patch. So don't have a patch that just uses "DBANC", even if the
>> previous patch did explain what it means. And if there's just one or two
>> "DBANC"s, just spell it out "DRM_BRIDGE_ATTACH_NO_CONNECTOR".
> 
> Yeah, I'd go even further. Acronyms are fun but something being obvious
> is better still. Use the proper flag name every time.
> 
> Maxime

Hi Maxime,

Thanks for pointing this out, will resend the series replacing the 
acronym with proper flag name.

Regards.