Re: [PATCH v6 05/30] drm/bridge: analogix_dp: Wait for HPD signal before configuring link

[Sasha Levin]

Hi,

[This is an automated email]

This commit has been processed by the -stable helper bot and determined
to be a high probability candidate for -stable trees. (score: 22.9952)

The bot has tested the following trees: v4.16, v4.15.15, v4.14.32, v4.9.92, 
v4.4.126.

v4.16: Failed to apply! Possible dependencies:
705e208c7389 ("drm/bridge: analogix_dp: Retry bridge enable when it failed")

v4.15.15: Failed to apply! Possible dependencies:
705e208c7389 ("drm/bridge: analogix_dp: Retry bridge enable when it failed")

v4.14.32: Failed to apply! Possible dependencies:
705e208c7389 ("drm/bridge: analogix_dp: Retry bridge enable when it failed")

v4.9.92: Failed to apply! Possible dependencies:
705e208c7389 ("drm/bridge: analogix_dp: Retry bridge enable when it failed")

v4.4.126: Failed to apply! Possible dependencies:
705e208c7389 ("drm/bridge: analogix_dp: Retry bridge enable when it failed")


Please let us know if you'd like to have this patch included in a stable tree.

--
Thanks,
Sasha
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[PATCH v6 05/30] drm/bridge: analogix_dp: Wait for HPD signal before configuring link

[Enric Balletbo i Serra]

From: zain wang 

According to DP spec v1.3 chap 3.5.1.2 Link Training, Link Policy Maker
must first detect that the HPD signal is asserted high by the Downstream
Device before establishing a link with it.

Cc: Stéphane Marchesin 
Signed-off-by: zain wang 
Signed-off-by: Sean Paul 
Signed-off-by: Thierry Escande 
Signed-off-by: Enric Balletbo i Serra 
Tested-by: Marek Szyprowski 
Reviewed-by: Archit Taneja 
---

 drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 11 +++
 1 file changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c 
b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
index bf805f156272..3269deec739d 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -1169,6 +1169,17 @@ static int analogix_dp_set_bridge(struct 
analogix_dp_device *dp)
if (ret)
goto out_dp_init;
 
+   /*
+* According to DP spec v1.3 chap 3.5.1.2 Link Training,
+* We should first make sure the HPD signal is asserted high by device
+* when we want to establish a link with it.
+*/
+   ret = analogix_dp_detect_hpd(dp);
+   if (ret) {
+   DRM_ERROR("failed to get hpd single ret = %d\n", ret);
+   goto out_dp_init;
+   }
+
ret = analogix_dp_commit(dp);
if (ret)
goto out_dp_init;
-- 
2.16.3

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