linux-kernel - Re: [PATCH] drm/rockchip: Suspend DP late

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Date:   Fri, 2 Aug 2019 15:26:29 -0400
From:   Sean Paul <sean@...rly.run>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Heiko Stuebner <heiko@...ech.de>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        seanpaul@...omium.org, linux-rockchip@...ts.infradead.org,
        mka@...omium.org, Sandy Huang <hjc@...k-chips.com>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        David Airlie <airlied@...ux.ie>,
        linux-arm-kernel@...ts.infradead.org,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH] drm/rockchip: Suspend DP late

On Fri, Aug 02, 2019 at 11:46:16AM -0700, Douglas Anderson wrote:
> In commit fe64ba5c6323 ("drm/rockchip: Resume DP early") we moved
> resume to be early but left suspend at its normal time.  This seems
> like it could be OK, but casues problems if a suspend gets interrupted
> partway through.  The OS only balances matching suspend/resume levels.
> ...so if suspend was called then resume will be called.  If suspend
> late was called then resume early will be called.  ...but if suspend
> was called resume early might not get called.  This leads to an
> unbalance in the clock enables / disables.
> 
> Lets take the simple fix and just move suspend to be late to match.
> This makes the PM core take proper care in keeping things balanced.
> 
> Fixes: fe64ba5c6323 ("drm/rockchip: Resume DP early")
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

Reviewed-by: Sean Paul <sean@...rly.run>

This should go in -misc-fixes and due to some... administrative reasons... I
will leave it on the list until Maarten has a chance to ff to -rc4 on Monday.
I'll apply it then so as to not require a backmerge.

Sean

> ---
> 
>  drivers/gpu/drm/rockchip/analogix_dp-rockchip.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c b/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c
> index 7d7cb57410fc..f38f5e113c6b 100644
> --- a/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c
> +++ b/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c
> @@ -436,7 +436,7 @@ static int rockchip_dp_resume(struct device *dev)
>  
>  static const struct dev_pm_ops rockchip_dp_pm_ops = {
>  #ifdef CONFIG_PM_SLEEP
> -	.suspend = rockchip_dp_suspend,
> +	.suspend_late = rockchip_dp_suspend,
>  	.resume_early = rockchip_dp_resume,
>  #endif
>  };
> -- 
> 2.22.0.770.g0f2c4a37fd-goog
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS