[PATCH v11 03/21] drm/bridge: synopsys: dw-dp: Fix error handling for DP link enablement

[Sebastian Reichel]

dw_dp_link_disable() may be called in atomic mode disable even when
dw_dp_link_enable() (or an earlier step) failed during atomic mode
enable as there is no error tracking. This would result in broken PHY
power state.

This is fixed by introducing a new enabled state in the link structure
to ensure the link disabling only happens if it has been properly
enabled in the first place.

The patch also adds missing error handling in dw_dp_link_enable()
itself to ensure the link enablement becomes an atomic operation.

Fixes: 86eecc3a9c2e ("drm/bridge: synopsys: Add DW DPTX Controller support library")
Reported-by: Sashiko <sashiko-bot at kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel at collabora.com>
---
 drivers/gpu/drm/bridge/synopsys/dw-dp.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-dp.c b/drivers/gpu/drm/bridge/synopsys/dw-dp.c
index d7945f7fe9f0..21d60e89126f 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-dp.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-dp.c
@@ -280,6 +280,7 @@ struct dw_dp_link {
 	unsigned char revision;
 	unsigned int rate;
 	unsigned int lanes;
+	bool enabled;
 	u8 sink_count;
 	u8 vsc_sdp_supported;
 	struct dw_dp_link_caps caps;
@@ -1615,6 +1616,9 @@ static void dw_dp_link_disable(struct dw_dp *dp)
 {
 	struct dw_dp_link *link = &dp->link;
 
+	if (!link->enabled)
+		return;
+
 	if (dw_dp_hpd_detect(dp))
 		drm_dp_link_power_down(&dp->aux, dp->link.revision);
 
@@ -1624,6 +1628,7 @@ static void dw_dp_link_disable(struct dw_dp *dp)
 
 	link->train.clock_recovered = false;
 	link->train.channel_equalized = false;
+	link->enabled = false;
 }
 
 static int dw_dp_link_enable(struct dw_dp *dp)
@@ -1636,10 +1641,22 @@ static int dw_dp_link_enable(struct dw_dp *dp)
 
 	ret = drm_dp_link_power_up(&dp->aux, dp->link.revision);
 	if (ret < 0)
-		return ret;
+		goto err_phy_power_off;
 
 	ret = dw_dp_link_train(dp);
+	if (ret < 0)
+		goto err_link_power_down;
+
+	dp->link.enabled = true;
 
+	return 0;
+
+err_link_power_down:
+	drm_dp_link_power_down(&dp->aux, dp->link.revision);
+	dw_dp_phy_xmit_enable(dp, 0);
+
+err_phy_power_off:
+	phy_power_off(dp->phy);
 	return ret;
 }
 

-- 
2.53.0