linux-kernel - Re: [v2] drm/msm: add shutdown support for display platform

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Message-ID: <cd61dd742e73b89794fc1b812d9fdcd9@codeaurora.org>
Date:   Tue, 02 Jun 2020 20:19:33 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Emil Velikov <emil.l.velikov@...il.com>
Cc:     Krishna Manikandan <mkrishn@...eaurora.org>,
        ML dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        freedreno@...ts.freedesktop.org,
        devicetree <devicetree@...r.kernel.org>,
        "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
        Sean Paul <seanpaul@...omium.org>, kalyan_t@...eaurora.org,
        "Kristian H . Kristensen" <hoegsberg@...omium.org>,
        mka@...omium.org, devicetree-owner@...r.kernel.org
Subject: Re: [v2] drm/msm: add shutdown support for display platform_driver

Hi Emil,

On 2020-06-02 19:43, Emil Velikov wrote:
> Hi Krishna,
> 
> On Tue, 2 Jun 2020 at 08:17, Krishna Manikandan 
> <mkrishn@...eaurora.org> wrote:
>> 
>> Define shutdown callback for display drm driver,
>> so as to disable all the CRTCS when shutdown
>> notification is received by the driver.
>> 
>> This change will turn off the timing engine so
>> that no display transactions are requested
>> while mmu translations are getting disabled
>> during reboot sequence.
>> 
>> Signed-off-by: Krishna Manikandan <mkrishn@...eaurora.org>
>> 
> AFAICT atomics is setup in msm_drm_ops::bind and shutdown in
> msm_drm_ops::unbind.
> 
> Are you saying that unbind never triggers? If so, then we should
> really fix that instead, since this patch seems more like a
> workaround.
> 

Which path do you suppose that the unbind should be called from, remove
callback? Here we are talking about the drivers which are builtin, where
remove callbacks are not called from the driver core during 
reboot/shutdown,
instead shutdown callbacks are called which needs to be defined in order 
to
trigger unbind. So AFAICS there is nothing to be fixed.

msm_pdev_shutdown()
  platform_drv_shutdown()
   device_shutdown()
    kernel_restart_prepare()
     kernel_restart()
      __arm64_sys_reboot()

Thanks,
Sai

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