linux-kernel - Re: [PATCH] drm/atomic: Check new_crtc_state->active to determine if CRTC needs disable in self refresh mode

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Message-ID: <CADnq5_PsxrYeZ+p5NbXRks3EaJrYNMN+vbUJkiKHZ4cf=x=dsg@mail.gmail.com>
Date:   Fri, 7 Jan 2022 14:53:39 -0500
From:   Alex Deucher <alexdeucher@...il.com>
To:     Liu Ying <victor.liu@....com>
Cc:     Maling list - DRI developers <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Rob Clark <robdclark@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        Sean Paul <seanpaul@...omium.org>,
        NXP Linux Team <linux-imx@....com>,
        Thomas Zimmermann <tzimmermann@...e.de>
Subject: Re: [PATCH] drm/atomic: Check new_crtc_state->active to determine if
 CRTC needs disable in self refresh mode

On Wed, Dec 29, 2021 at 11:07 PM Liu Ying <victor.liu@....com> wrote:
>
> Actual hardware state of CRTC is controlled by the member 'active' in
> struct drm_crtc_state instead of the member 'enable', according to the
> kernel doc of the member 'enable'.  In fact, the drm client modeset
> and atomic helpers are using the member 'active' to do the control.
>
> Referencing the member 'enable' of new_crtc_state, the function
> crtc_needs_disable() may fail to reflect if CRTC needs disable in
> self refresh mode, e.g., when the framebuffer emulation will be blanked
> through the client modeset helper with the next commit, the member
> 'enable' of new_crtc_state is still true while the member 'active' is
> false, hence the relevant potential encoder and bridges won't be disabled.
>
> So, let's check new_crtc_state->active to determine if CRTC needs disable
> in self refresh mode instead of new_crtc_state->enable.
>
> Fixes: 1452c25b0e60 ("drm: Add helpers to kick off self refresh mode in drivers")
> Cc: Sean Paul <seanpaul@...omium.org>
> Cc: Rob Clark <robdclark@...omium.org>
> Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
> Cc: Maxime Ripard <mripard@...nel.org>
> Cc: Thomas Zimmermann <tzimmermann@...e.de>
> Cc: David Airlie <airlied@...ux.ie>
> Cc: Daniel Vetter <daniel@...ll.ch>
> Signed-off-by: Liu Ying <victor.liu@....com>

Reviewed-by: Alex Deucher <alexander.deucher@....com>

Do you need someone to push this for you?

Alex

> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index a7a05e1e26bb..9603193d2fa1 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -1016,7 +1016,7 @@ crtc_needs_disable(struct drm_crtc_state *old_state,
>          * it's in self refresh mode and needs to be fully disabled.
>          */
>         return old_state->active ||
> -              (old_state->self_refresh_active && !new_state->enable) ||
> +              (old_state->self_refresh_active && !new_state->active) ||
>                new_state->self_refresh_active;
>  }
>
> --
> 2.25.1
>