[PATCH v12 12/23] drm/bridge: synopsys: dw-dp: Support software triggered OOB HPD

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

Add support for USB-C DP AltMode out-of-band hotplug handling. The
handling itself is implemented in the platform specific driver as the
registers to force HPD state are not part of the Designware DisplayPort
IP itself. Instead the platform integration might provide the necessary
functionality to mux the HPD signal.

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 | 41 +++++++++++++++++++++++++++++++++
 include/drm/bridge/dw_dp.h              |  3 +++
 2 files changed, 44 insertions(+)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-dp.c b/drivers/gpu/drm/bridge/synopsys/dw-dp.c
index 74ba1306caee..b4eed4d0a520 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-dp.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-dp.c
@@ -1875,6 +1875,19 @@ static struct drm_bridge_state *dw_dp_bridge_atomic_duplicate_state(struct drm_b
 	return &state->base;
 }
 
+static bool dw_dp_is_routed_to_usb_c(struct drm_encoder *encoder)
+{
+	struct drm_bridge *last_bridge __free(drm_bridge_put) = NULL;
+	struct fwnode_handle *fwnode;
+
+	last_bridge = drm_bridge_chain_get_last_bridge(encoder);
+	if (!last_bridge)
+		return false;
+
+	fwnode = of_fwnode_handle(last_bridge->of_node);
+	return fwnode_device_is_compatible(fwnode, "usb-c-connector");
+}
+
 static int dw_dp_bridge_attach(struct drm_bridge *bridge,
 			       struct drm_encoder *encoder,
 			       enum drm_bridge_attach_flags flags)
@@ -1903,6 +1916,13 @@ static int dw_dp_bridge_attach(struct drm_bridge *bridge,
 		goto err_disable_irq;
 	}
 
+	if (dw_dp_is_routed_to_usb_c(encoder)) {
+		dev_dbg(dev, "USB-C mode\n");
+
+		if (dp->plat_data.hpd_sw_sel)
+			dp->plat_data.hpd_sw_sel(dp->plat_data.data, 1);
+	}
+
 	return 0;
 
 err_disable_irq:
@@ -1923,6 +1943,22 @@ static void dw_dp_bridge_detach(struct drm_bridge *bridge)
 	drm_dp_aux_unregister(&dp->aux);
 }
 
+static void dw_dp_bridge_oob_notify(struct drm_bridge *bridge,
+				    struct drm_connector *connector,
+				    enum drm_connector_status status)
+{
+	bool hpd_high = status != connector_status_disconnected;
+	struct dw_dp *dp = bridge_to_dp(bridge);
+
+	if (!dp->plat_data.hpd_sw_cfg) {
+		dev_err_once(dp->dev, "Missing platform handler for OOB HPD handling\n");
+		return;
+	}
+
+	dev_dbg(dp->dev, "Force HPD connected=%s\n", str_yes_no(hpd_high));
+	dp->plat_data.hpd_sw_cfg(dp->plat_data.data, hpd_high);
+}
+
 static const struct drm_bridge_funcs dw_dp_bridge_funcs = {
 	.attach = dw_dp_bridge_attach,
 	.detach = dw_dp_bridge_detach,
@@ -1937,6 +1973,7 @@ static const struct drm_bridge_funcs dw_dp_bridge_funcs = {
 	.atomic_disable = dw_dp_bridge_atomic_disable,
 	.detect = dw_dp_bridge_detect,
 	.edid_read = dw_dp_bridge_edid_read,
+	.oob_notify = dw_dp_bridge_oob_notify,
 };
 
 static int dw_dp_link_retrain(struct dw_dp *dp)
@@ -2105,6 +2142,10 @@ struct dw_dp *dw_dp_probe(struct platform_device *pdev, const struct dw_dp_plat_
 
 	dp->dev = dev;
 	dp->pixel_mode = plat_data->pixel_mode;
+
+	dp->plat_data.hpd_sw_sel = plat_data->hpd_sw_sel;
+	dp->plat_data.hpd_sw_cfg = plat_data->hpd_sw_cfg;
+	dp->plat_data.data = plat_data->data;
 	dp->plat_data.max_link_rate = plat_data->max_link_rate;
 
 	INIT_WORK(&dp->hpd_work, dw_dp_hpd_work);
diff --git a/include/drm/bridge/dw_dp.h b/include/drm/bridge/dw_dp.h
index a82412a9e769..79b2cdf0df99 100644
--- a/include/drm/bridge/dw_dp.h
+++ b/include/drm/bridge/dw_dp.h
@@ -20,6 +20,9 @@ enum {
 struct dw_dp_plat_data {
 	u32 max_link_rate;
 	u8 pixel_mode;
+	void *data;
+	void (*hpd_sw_sel)(void *data, bool hpd);
+	void (*hpd_sw_cfg)(void *data, bool hpd);
 };
 
 int dw_dp_bind(struct dw_dp *dp, struct drm_encoder *encoder);

-- 
2.53.0