linux-kernel - Re: [PATCH v2 8/8] drm/amdgpu: Call drm_atomic_helper

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Date: Mon, 17 Jun 2024 11:01:24 -0400
From: Alex Deucher <alexdeucher@...il.com>
To: Douglas Anderson <dianders@...omium.org>
Cc: dri-devel@...ts.freedesktop.org, Maxime Ripard <mripard@...nel.org>, 
	Alex Deucher <alexander.deucher@....com>, Christian König <christian.koenig@....com>, 
	Xinhui Pan <Xinhui.Pan@....com>, André Almeida <andrealmeid@...lia.com>, 
	Aurabindo Pillai <aurabindo.pillai@....com>, Candice Li <candice.li@....com>, 
	Daniel Vetter <daniel@...ll.ch>, David Airlie <airlied@...il.com>, 
	Hamza Mahfooz <hamza.mahfooz@....com>, Hawking Zhang <Hawking.Zhang@....com>, Le Ma <le.ma@....com>, 
	Lijo Lazar <lijo.lazar@....com>, Ma Jun <Jun.Ma2@....com>, 
	Mario Limonciello <mario.limonciello@....com>, Shashank Sharma <shashank.sharma@....com>, 
	Srinivasan Shanmugam <srinivasan.shanmugam@....com>, Thomas Zimmermann <tzimmermann@...e.de>, 
	Victor Lu <victorchengchi.lu@....com>, amd-gfx@...ts.freedesktop.org, 
	chenxuebing <chenxb_99091@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 8/8] drm/amdgpu: Call drm_atomic_helper_shutdown() at
 shutdown time

On Wed, Jun 12, 2024 at 6:37 PM Douglas Anderson <dianders@...omium.org> wrote:
>
> Based on grepping through the source code this driver appears to be
> missing a call to drm_atomic_helper_shutdown() at system shutdown
> time. Among other things, this means that if a panel is in use that it
> won't be cleanly powered off at system shutdown time.
>
> The fact that we should call drm_atomic_helper_shutdown() in the case
> of OS shutdown/restart comes straight out of the kernel doc "driver
> instance overview" in drm_drv.c.
>
> Suggested-by: Maxime Ripard <mripard@...nel.org>
> Cc: Alex Deucher <alexander.deucher@....com>
> Cc: Christian König <christian.koenig@....com>
> Cc: Xinhui Pan <Xinhui.Pan@....com>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
> This commit is only compile-time tested.
>
> ...and further, I'd say that this patch is more of a plea for help
> than a patch I think is actually right. I'm _fairly_ certain that
> drm/amdgpu needs this call at shutdown time but the logic is a bit
> hard for me to follow. I'd appreciate if anyone who actually knows
> what this should look like could illuminate me, or perhaps even just
> post a patch themselves!

I'm not sure this patch makes sense or not.  The driver doesn't really
do a formal tear down in its shutdown routine, it just quiesces the
hardware.  What are the actual requirements of the shutdown function?
In the past when we did a full driver tear down in shutdown, it
delayed the shutdown sequence and users complained.

Alex

>
> (no changes since v1)
>
>  drivers/gpu/drm/amd/amdgpu/amdgpu.h        |  1 +
>  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 10 ++++++++++
>  drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c    |  2 ++
>  3 files changed, 13 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index f87d53e183c3..c202a1d5ff5f 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -1197,6 +1197,7 @@ static inline struct amdgpu_device *amdgpu_ttm_adev(struct ttm_device *bdev)
>  int amdgpu_device_init(struct amdgpu_device *adev,
>                        uint32_t flags);
>  void amdgpu_device_fini_hw(struct amdgpu_device *adev);
> +void amdgpu_device_shutdown_hw(struct amdgpu_device *adev);
>  void amdgpu_device_fini_sw(struct amdgpu_device *adev);
>
>  int amdgpu_gpu_wait_for_idle(struct amdgpu_device *adev);
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index 861ccff78af9..a8c4b8412e04 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -4531,6 +4531,16 @@ void amdgpu_device_fini_hw(struct amdgpu_device *adev)
>
>  }
>
> +void amdgpu_device_shutdown_hw(struct amdgpu_device *adev)
> +{
> +       if (adev->mode_info.mode_config_initialized) {
> +               if (!drm_drv_uses_atomic_modeset(adev_to_drm(adev)))
> +                       drm_helper_force_disable_all(adev_to_drm(adev));
> +               else
> +                       drm_atomic_helper_shutdown(adev_to_drm(adev));
> +       }
> +}
> +
>  void amdgpu_device_fini_sw(struct amdgpu_device *adev)
>  {
>         int idx;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> index ea14f1c8f430..b34bf9259d5c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
> @@ -2409,6 +2409,8 @@ amdgpu_pci_shutdown(struct pci_dev *pdev)
>         struct drm_device *dev = pci_get_drvdata(pdev);
>         struct amdgpu_device *adev = drm_to_adev(dev);
>
> +       amdgpu_device_shutdown_hw(adev);
> +
>         if (amdgpu_ras_intr_triggered())
>                 return;
>
> --
> 2.45.2.505.gda0bf45e8d-goog
>