linux-kernel - Re: [PATCH] drm/msm/dpu: ensure device suspend happens during PM sleep

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Message-ID: <2922a0c64ec61c3d74d516e44dca2d71@codeaurora.org>
Date:   Wed, 01 Apr 2020 15:02:21 +0530
From:   kalyan_t@...eaurora.org
To:     Doug Anderson <dianders@...omium.org>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Rob Clark <robdclark@...il.com>,
        Sean Paul <seanpaul@...omium.org>,
        "Kristian H. Kristensen" <hoegsberg@...omium.org>,
        Jeykumar Sankaran <jsanka@...eaurora.org>,
        mkrishn@...eaurora.org, travitej@...eaurora.org,
        nganji@...eaurora.org
Subject: Re: [PATCH] drm/msm/dpu: ensure device suspend happens during PM
 sleep

On 2020-03-31 21:30, Doug Anderson wrote:
> Hi,
> 
> On Tue, Mar 31, 2020 at 6:58 AM Kalyan Thota <kalyan_t@...eaurora.org> 
> wrote:
>> 
>> "The PM core always increments the runtime usage counter
>> before calling the ->suspend() callback and decrements it
>> after calling the ->resume() callback"
>> 
>> DPU and DSI are managed as runtime devices. When
>> suspend is triggered, PM core adds a refcount on all the
>> devices and calls device suspend, since usage count is
>> already incremented, runtime suspend was not getting called
>> and it kept the clocks on which resulted in target not
>> entering into XO shutdown.
>> 
>> Add changes to force suspend on runtime devices during pm sleep.
>> 
>> Changes in v1:
>>  - Remove unnecessary checks in the function
>>     _dpu_kms_disable_dpu (Rob Clark).
>> 
>> Changes in v2:
>>  - Avoid using suspend_late to reset the usagecount
>>    as suspend_late might not be called during suspend
>>    call failures (Doug).
>> 
>> Changes in v3:
>>  - Use force suspend instead of managing device usage_count
>>    via runtime put and get API's to trigger callbacks (Doug).
>> 
>> Signed-off-by: Kalyan Thota <kalyan_t@...eaurora.org>
>> ---
>>  drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 2 ++
>>  drivers/gpu/drm/msm/dsi/dsi.c           | 2 ++
>>  drivers/gpu/drm/msm/msm_drv.c           | 4 ++++
>>  3 files changed, 8 insertions(+)
> 
> This looks much saner to me.  Thanks!  I assume it still works fine
> for you?  I'm still no expert on how all the pieces of DRM drivers
> work together, but at least there's not a bunch of strange fiddling
> with pm_runtime state and hopefully it will avoid weird corner
> cases...
> 
--- Yes, verified the change on trogdor device, and display can suspend 
with the change.
> 
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c 
>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>> index ce19f1d..b886d9d 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>> @@ -1123,6 +1123,8 @@ static int __maybe_unused 
>> dpu_runtime_resume(struct device *dev)
>> 
>>  static const struct dev_pm_ops dpu_pm_ops = {
>>         SET_RUNTIME_PM_OPS(dpu_runtime_suspend, dpu_runtime_resume, 
>> NULL)
>> +       SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
>> +                               pm_runtime_force_resume)
>>  };
>> 
>>  static const struct of_device_id dpu_dt_match[] = {
>> diff --git a/drivers/gpu/drm/msm/dsi/dsi.c 
>> b/drivers/gpu/drm/msm/dsi/dsi.c
>> index 55ea4bc2..62704885 100644
>> --- a/drivers/gpu/drm/msm/dsi/dsi.c
>> +++ b/drivers/gpu/drm/msm/dsi/dsi.c
>> @@ -161,6 +161,8 @@ static int dsi_dev_remove(struct platform_device 
>> *pdev)
>> 
>>  static const struct dev_pm_ops dsi_pm_ops = {
>>         SET_RUNTIME_PM_OPS(msm_dsi_runtime_suspend, 
>> msm_dsi_runtime_resume, NULL)
>> +       SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
>> +                               pm_runtime_force_resume)
>>  };
>> 
>>  static struct platform_driver dsi_driver = {
>> diff --git a/drivers/gpu/drm/msm/msm_drv.c 
>> b/drivers/gpu/drm/msm/msm_drv.c
>> index 7d985f8..2b8c99c 100644
>> --- a/drivers/gpu/drm/msm/msm_drv.c
>> +++ b/drivers/gpu/drm/msm/msm_drv.c
>> @@ -1051,6 +1051,8 @@ static int msm_pm_suspend(struct device *dev)
>>                 return ret;
>>         }
>> 
>> +       pm_runtime_force_suspend(dev);
> 
> nit: check return value of pm_runtime_force_suspend()?
> 
> 
>> +
>>         return 0;
>>  }
>> 
>> @@ -1063,6 +1065,8 @@ static int msm_pm_resume(struct device *dev)
>>         if (WARN_ON(!priv->pm_state))
>>                 return -ENOENT;
>> 
>> +       pm_runtime_force_resume(dev);
> 
> nit: check return value of pm_runtime_force_resume()?
> 
> 
> -Doug