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From: Stephen Boyd <swboyd@chromium.org>
To: Maxime Ripard <maxime@cerno.tech>
Cc: dri-devel@lists.freedesktop.org,
	Daniel Vetter <daniel.vetter@intel.com>,
	David Airlie <airlied@linux.ie>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	Rob Clark <robdclark@gmail.com>,
	linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org
Subject: Re: [PATCH v3 10/11] drm: Use state helper instead of the plane state pointer
Date: Mon, 29 Mar 2021 18:52:01 -0700
Message-ID: <161706912161.3012082.17313817257247946143@swboyd.mtv.corp.google.com> (raw)
In-Reply-To: <20210219120032.260676-10-maxime@cerno.tech>

Trimming Cc list way down, sorry if that's too much.

Quoting Maxime Ripard (2021-02-19 04:00:30)
> Many drivers reference the plane->state pointer in order to get the
> current plane state in their atomic_update or atomic_disable hooks,
> which would be the new plane state in the global atomic state since
> _swap_state happened when those hooks are run.

Does this mean drm_atomic_helper_swap_state()?

> 
> Use the drm_atomic_get_new_plane_state helper to get that state to make it
> more obvious.
> 
> This was made using the coccinelle script below:
> 
> @ plane_atomic_func @
> identifier helpers;
> identifier func;
> @@
> 
> (
>  static const struct drm_plane_helper_funcs helpers = {
>         ...,
>         .atomic_disable = func,
>         ...,
>  };
> |
>  static const struct drm_plane_helper_funcs helpers = {
>         ...,
>         .atomic_update = func,
>         ...,
>  };
> )
> 
> @ adds_new_state @
> identifier plane_atomic_func.func;
> identifier plane, state;
> identifier new_state;
> @@
> 
>  func(struct drm_plane *plane, struct drm_atomic_state *state)
>  {
>         ...
> -       struct drm_plane_state *new_state = plane->state;
> +       struct drm_plane_state *new_state = drm_atomic_get_new_plane_state(state, plane);
>         ...
>  }
> 
> @ include depends on adds_new_state @
> @@
> 
>  #include <drm/drm_atomic.h>
> 
> @ no_include depends on !include && adds_new_state @
> @@
> 
> + #include <drm/drm_atomic.h>
>   #include <drm/...>
> 
>  drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c       | 3 ++-
>  drivers/gpu/drm/msm/disp/mdp4/mdp4_plane.c      | 4 +++-
>  drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c      | 3 ++-
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> index 31071f9e21d7..e8ce72fe54a4 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> @@ -1244,7 +1244,8 @@ static void dpu_plane_atomic_update(struct drm_plane *plane,
>                                 struct drm_atomic_state *state)
>  {
>         struct dpu_plane *pdpu = to_dpu_plane(plane);
> -       struct drm_plane_state *new_state = plane->state;
> +       struct drm_plane_state *new_state = drm_atomic_get_new_plane_state(state,
> +                                                                          plane);
>  
>         pdpu->is_error = false;
>  

This is oopsing for me. It turns out that 'new_state' is NULL. According
to the comments drm_atomic_get_new_plane_state() can return NULL if the
plane isn't part of the global state. I haven't looked much further but
wanted to report it here in case that type of return value makes sense.

If I revert this patch from linux-next my display works and doesn't
crash the system. Or I can check for NULL in the if below and it also
works.

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
index df7f3d3afd8b..f31b89531f6a 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
@@ -1251,7 +1251,7 @@ static void dpu_plane_atomic_update(struct drm_plane *plane,
 
 	DPU_DEBUG_PLANE(pdpu, "\n");
 
-	if (!new_state->visible) {
+	if (new_state && !new_state->visible) {
 		_dpu_plane_atomic_disable(plane);
 	} else {
 		dpu_plane_sspp_atomic_update(plane);

  reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-19 12:00 [PATCH v3 01/11] drm/atomic: Pass the full state to planes async atomic check and update Maxime Ripard
2021-02-19 12:00 ` [PATCH v3 02/11] drm: Rename plane atomic_check state names Maxime Ripard
2021-02-19 14:49   ` Thomas Zimmermann
2021-02-19 15:12     ` Maxime Ripard
2021-02-22  9:01       ` Thomas Zimmermann
2021-02-19 12:00 ` [PATCH v3 04/11] drm/atomic: Pass the full state to planes atomic_check Maxime Ripard
2021-02-22  9:00   ` Thomas Zimmermann
2021-02-19 12:00 ` [PATCH v3 05/11] drm: Use the state pointer directly in " Maxime Ripard
2021-02-22  9:05   ` Thomas Zimmermann
2021-02-19 12:00 ` [PATCH v3 06/11] drm: Use state helper instead of plane state pointer in atomic_check Maxime Ripard
2021-02-22  9:12   ` Thomas Zimmermann
2021-02-23 14:41     ` Maxime Ripard
2021-02-19 12:00 ` [PATCH v3 08/11] drm: Rename plane->state variables in atomic update and disable Maxime Ripard
2021-02-19 12:00 ` [PATCH v3 09/11] drm/atomic: Pass the full state to planes atomic disable and update Maxime Ripard
2021-02-19 12:00 ` [PATCH v3 10/11] drm: Use state helper instead of the plane state pointer Maxime Ripard
2021-03-30  1:52   ` Stephen Boyd [this message]
2021-03-30 15:35     ` Maxime Ripard
2021-03-30 18:56       ` Stephen Boyd
2021-04-08 13:20         ` Maxime Ripard
2021-04-30 16:44           ` Rob Clark
2021-05-04  7:40             ` Daniel Vetter
2021-02-24 11:33 ` [PATCH v3 01/11] drm/atomic: Pass the full state to planes async atomic check and update Thomas Zimmermann
2021-02-25  7:08   ` Maxime Ripard

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