[PATCH v12 19/23] drm/bridge: synopsys: dw-dp: Clear only enabled SDPs on atomic disable

[Sebastian Reichel <sebastian.reichel@collabora.com>]

dw_dp_bridge_atomic_disable() bulk-cleared the whole SDP register bank
allocation bitmap via bitmap_zero() resulting in the loss of all
tracking information. This results in a slot potentially being handed
out again by dw_dp_send_sdp(), which is still considered to be held
by the previous owner. Then the previous owner might free up the wrong
SDP later on.

Instead of bulk clearing the tracking information, the new
implementation only clears the SDPs actually configured during
dw_dp_bridge_atomic_enable() instead of the entire bank. The
introduced functionality for that will also be used by the to-be-added
audio infrastructure.

Tested-by: Igor Paunovic <royalnet026@gmail.com> # Orange Pi 5+
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
---
 drivers/gpu/drm/bridge/synopsys/dw-dp.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-dp.c b/drivers/gpu/drm/bridge/synopsys/dw-dp.c
index 1ae5c842a782..6e165e39b1f8 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-dp.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-dp.c
@@ -335,6 +335,7 @@ struct dw_dp {
 	bool usbc_hpd;
 	bool pm_active;
 
+	int vsc_sdp_nr;
 	DECLARE_BITMAP(sdp_reg_bank, SDP_REG_BANK_SIZE);
 };
 
@@ -1076,7 +1077,19 @@ static int dw_dp_send_sdp(struct dw_dp *dp, struct dw_dp_sdp *sdp)
 				   EN_HORIZONTAL_SDP << nr,
 				   EN_HORIZONTAL_SDP << nr);
 
-	return 0;
+	return nr;
+}
+
+static void dw_dp_clear_sdp(struct dw_dp *dp, int nr)
+{
+	regmap_clear_bits(dp->regmap, DW_DP_SDP_VERTICAL_CTRL,
+			  EN_VERTICAL_SDP << nr);
+
+	regmap_clear_bits(dp->regmap, DW_DP_SDP_HORIZONTAL_CTRL,
+			  EN_HORIZONTAL_SDP << nr);
+
+	scoped_guard(mutex, &dp->sdp_lock)
+		clear_bit(nr, dp->sdp_reg_bank);
 }
 
 static int dw_dp_send_vsc_sdp(struct dw_dp *dp)
@@ -1394,7 +1407,7 @@ static int dw_dp_video_enable(struct dw_dp *dp)
 			   FIELD_PREP(VIDEO_STREAM_ENABLE, 1));
 
 	if (dw_dp_video_need_vsc_sdp(dp))
-		dw_dp_send_vsc_sdp(dp);
+		dp->vsc_sdp_nr = dw_dp_send_vsc_sdp(dp);
 
 	return 0;
 }
@@ -1754,8 +1767,12 @@ static void dw_dp_bridge_atomic_disable(struct drm_bridge *bridge,
 
 	dw_dp_video_disable(dp);
 	dw_dp_link_disable(dp);
-	scoped_guard(mutex, &dp->sdp_lock)
-		bitmap_zero(dp->sdp_reg_bank, SDP_REG_BANK_SIZE);
+
+	if (dp->vsc_sdp_nr >= 0) {
+		dw_dp_clear_sdp(dp, dp->vsc_sdp_nr);
+		dp->vsc_sdp_nr = -1;
+	}
+
 	dw_dp_reset(dp);
 	pm_runtime_put_autosuspend(dp->dev);
 }
@@ -2352,6 +2369,8 @@ int dw_dp_probe(struct dw_dp *dp)
 	if (ret)
 		return ret;
 
+	dp->vsc_sdp_nr = -1;
+
 	bridge = &dp->bridge;
 	bridge->of_node = dev->of_node;
 	bridge->ops = DRM_BRIDGE_OP_DETECT | DRM_BRIDGE_OP_EDID | DRM_BRIDGE_OP_HPD;

-- 
2.53.0