[PATCH v7 17/18] drm/bridge: synopsys: dw-dp: Clear only enabled SDPs on atomic disable

[Sebastian Reichel]

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.

Signed-off-by: Sebastian Reichel <sebastian.reichel at collabora.com>
---
 drivers/gpu/drm/bridge/synopsys/dw-dp.c | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-dp.c b/drivers/gpu/drm/bridge/synopsys/dw-dp.c
index fcee47c6716a..c0026bd4c7b5 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-dp.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-dp.c
@@ -336,6 +336,7 @@ struct dw_dp {
 
 	struct drm_bridge *next_bridge;
 
+	int vsc_sdp_nr;
 	DECLARE_BITMAP(sdp_reg_bank, SDP_REG_BANK_SIZE);
 };
 
@@ -1075,7 +1076,19 @@ static int dw_dp_send_sdp(struct dw_dp *dp, struct dw_dp_sdp *sdp)
 		regmap_set_bits(dp->regmap, DW_DP_SDP_HORIZONTAL_CTRL,
 				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)
@@ -1393,7 +1406,7 @@ 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;
 }
@@ -1738,8 +1751,14 @@ static void dw_dp_bridge_atomic_disable(struct drm_bridge *bridge,
 
 	dw_dp_video_disable(dp);
 	dw_dp_link_disable(dp);
+
+	if (dp->vsc_sdp_nr >= 0) {
+		dw_dp_clear_sdp(dp, dp->vsc_sdp_nr);
+		dp->vsc_sdp_nr = -1;
+	}
 	scoped_guard(mutex, &dp->sdp_lock)
-		bitmap_zero(dp->sdp_reg_bank, SDP_REG_BANK_SIZE);
+		clear_bit(0, dp->sdp_reg_bank);
+
 	dw_dp_reset(dp);
 	pm_runtime_put_autosuspend(dp->dev);
 }
@@ -2191,6 +2210,8 @@ struct dw_dp *dw_dp_probe(struct platform_device *pdev, const struct dw_dp_plat_
 	dp->plat_data.data = plat_data->data;
 	dp->plat_data.max_link_rate = plat_data->max_link_rate;
 
+	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