Hi Laurent,

On 2018-02-21 13:49, Laurent Pinchart wrote:
Thank you for the patch.

On Wednesday, 21 February 2018 12:04:43 EET Marek Szyprowski wrote:
Patch f0a8b49c03d2 ("drm/bridge: analogix dp: Fix runtime PM state on
driver bind") fixed unbalanced call to phy_power_on() in analogix_dp_bind()
function by calling phy_power_off() at the end of bind operation.

However it turned out that having PHY powered is required for proper DRM
display pipeline initialization on Peach-Pit Chromebook2 board, as this
board freezes otherwise when PHY power off is called in bind. Fix this by
keeping PHY powered for the whole bind/unbind driver life cycle. The
freeze is probably related to the fact that the display pipeline (Exynos
FIMD CTRC -> Exynos/Analogix DP bridge -> PS8625 dp2lvds bridge -> B116XW03
panel) is already configured and enabled by the bootloader and require
reset of all components for proper shutdown.
"Probably" always makes me feel uncomfortable in such a context :-) Leaving
the PHY powered at all times isn't the best idea as it will increase power
consumption even when the DP output isn't in use. I can live with that if
there's no other way, but it feels to me like we should first get to the
bottom of the issue.

Frankly I spent some time on this and I have no other idea. Board freezes when phy_power_off is called and the initial code worked properly on that board by
leaking phy turned on all the time.

Having PHY powered is also needed for proper EDID handling, which initially
fixed by commit 510353a63796 ("drm/bridge: analogix dp: Fix runtime PM state
in get_modes() callback").

Fixes: f0a8b49c03d2 ("drm/bridge: analogix dp: Fix runtime PM state on
driver bind")
Signed-off-by: Marek Szyprowski <m.szyprow...@samsung.com>
  drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c index
b2756bc4225a..42595863cb03 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -1415,7 +1415,6 @@ int analogix_dp_bind(struct device *dev, struct
drm_device *drm_dev, goto err_disable_pm_runtime;

-       phy_power_off(dp->phy);

        return 0;
@@ -1448,6 +1447,7 @@ void analogix_dp_unbind(struct device *dev, struct
device *master,

+       phy_power_off(dp->phy);

Best regards
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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