Re: [PATCH] drm/msm/dpu: Delete bonkers code

From: Stephen Boyd <swboyd@chromium.org>
To: Rob Clark <robdclark@gmail.com>, dri-devel@lists.freedesktop.org
Cc: "Maxime Ripard" <maxime@cerno.tech>,
	"Rob Clark" <robdclark@chromium.org>,
	"John Stultz" <john.stultz@linaro.org>,
	"Sean Paul" <sean@poorly.run>, "David Airlie" <airlied@linux.ie>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"Abhinav Kumar" <abhinavk@codeaurora.org>,
	"Thomas Zimmermann" <tzimmermann@suse.de>,
	"Stephen Boyd" <swboyd@chromium.org>,
	"Kalyan Thota" <kalyan_t@codeaurora.org>,
	"Hongbo Yao" <yaohongbo@huawei.com>,
	"Qinglang Miao" <miaoqinglang@huawei.com>,
	"Laurent Pinchart" <laurent.pinchart@ideasonboard.com>,
	"Lee Jones" <lee.jones@linaro.org>,
	"Ville Syrjälä" <ville.syrjala@linux.intel.com>,
	linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drm/msm/dpu: Delete bonkers code
Date: Fri, 30 Apr 2021 10:44:53 -0700	[thread overview]
Message-ID: <CAE-0n513cwqs1c89PZpn0ojuDQ44nwxbRfaYssKHcGwKxK8JdA@mail.gmail.com> (raw)
In-Reply-To: <20210430171744.1721408-1-robdclark@gmail.com>

Quoting Rob Clark (2021-04-30 10:17:39)
> From: Rob Clark <robdclark@chromium.org>
>
> dpu_crtc_atomic_flush() was directly poking it's attached planes in a
> code path that ended up in dpu_plane_atomic_update(), even if the plane
> was not involved in the current atomic update.  While a bit dubious,
> this worked before because plane->state would always point to something
> valid.  But now using drm_atomic_get_new_plane_state() we could get a
> NULL state pointer instead, leading to:
>
>    [   20.873273] Call trace:
>    [   20.875740]  dpu_plane_atomic_update+0x5c/0xed0
>    [   20.880311]  dpu_plane_restore+0x40/0x88
>    [   20.884266]  dpu_crtc_atomic_flush+0xf4/0x208
>    [   20.888660]  drm_atomic_helper_commit_planes+0x150/0x238
>    [   20.894014]  msm_atomic_commit_tail+0x1d4/0x7a0
>    [   20.898579]  commit_tail+0xa4/0x168
>    [   20.902102]  drm_atomic_helper_commit+0x164/0x178
>    [   20.906841]  drm_atomic_commit+0x54/0x60
>    [   20.910798]  drm_atomic_connector_commit_dpms+0x10c/0x118
>    [   20.916236]  drm_mode_obj_set_property_ioctl+0x1e4/0x440
>    [   20.921588]  drm_connector_property_set_ioctl+0x60/0x88
>    [   20.926852]  drm_ioctl_kernel+0xd0/0x120
>    [   20.930807]  drm_ioctl+0x21c/0x478
>    [   20.934235]  __arm64_sys_ioctl+0xa8/0xe0
>    [   20.938193]  invoke_syscall+0x64/0x130
>    [   20.941977]  el0_svc_common.constprop.3+0x5c/0xe0
>    [   20.946716]  do_el0_svc+0x80/0xa0
>    [   20.950058]  el0_svc+0x20/0x30
>    [   20.953145]  el0_sync_handler+0x88/0xb0
>    [   20.957014]  el0_sync+0x13c/0x140
>
> The reason for the codepath seems dubious, the atomic suspend/resume
> heplers should handle the power-collapse case.  If not, the CRTC's
> atomic_check() should be adding the planes to the atomic update.
>
> Reported-by: Stephen Boyd <sboyd@kernel.org>

Maybe better to use swboyd@chromium.org for this one.

> Reported-by: John Stultz <john.stultz@linaro.org>
> Fixes: 37418bf14c13 drm: Use state helper instead of the plane state pointer

Should be

Fixes: 37418bf14c13 ("drm: Use state helper instead of the plane state pointer")

to match the preferred format.

> Signed-off-by: Rob Clark <robdclark@chromium.org>

Otherwise looks good, thanks.