Re: [PATCH] drm/bridge: analogix_dp: Keep PHY powered from between driver bind/unbind

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Marek,

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.

> 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.szyprowski@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);
>  	pm_runtime_put(dev);
> 
>  	return 0;
> @@ -1448,6 +1447,7 @@ void analogix_dp_unbind(struct device *dev, struct
> device *master,
> 
>  	drm_dp_aux_unregister(&dp->aux);
>  	pm_runtime_disable(dev);
> +	phy_power_off(dp->phy);
>  	clk_disable_unprepare(dp->clock);
>  }
>  EXPORT_SYMBOL_GPL(analogix_dp_unbind);

-- 
Regards,

Laurent Pinchart

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