linux-kernel - Re: [PATCH v5 5/5] drm/amdgpu: do not resume device in thaw for normal hibernation

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Message-ID: <202dae4c-6280-4f35-9c16-fdf6398ba856@amd.com>
Date: Thu, 10 Jul 2025 09:48:49 +0530
From: "Lazar, Lijo" <lijo.lazar@....com>
To: Mario Limonciello <mario.limonciello@....com>,
 Samuel Zhang <guoqing.zhang@....com>, alexander.deucher@....com,
 christian.koenig@....com, rafael@...nel.org, len.brown@...el.com,
 pavel@...nel.org, gregkh@...uxfoundation.org, dakr@...nel.org,
 airlied@...il.com, simona@...ll.ch, ray.huang@....com,
 matthew.auld@...el.com, matthew.brost@...el.com,
 maarten.lankhorst@...ux.intel.com, mripard@...nel.org, tzimmermann@...e.de
Cc: victor.zhao@....com, haijun.chang@....com, Qing.Ma@....com,
 Owen.Zhang2@....com, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v5 5/5] drm/amdgpu: do not resume device in thaw for
 normal hibernation



On 7/10/2025 1:20 AM, Mario Limonciello wrote:
> On 7/9/2025 6:05 AM, Samuel Zhang wrote:
>> For normal hibernation, GPU do not need to be resumed in thaw since it is
>> not involved in writing the hibernation image. Skip resume in this case
>> can reduce the hibernation time.
>>
>> On VM with 8 * 192GB VRAM dGPUs, 98% VRAM usage and 1.7TB system memory,
>> this can save 50 minutes.
>>
>> Signed-off-by: Samuel Zhang <guoqing.zhang@....com>
> 
> I hand modified the patches for other changes missing from linux-next in
> your base.
> 
> I checked on an APU with an eDP display connected and from a VT
> hibernate does keep the display off now so this is definitely an
> improvement there too.
> 
> Tested-by: Mario Limonciello <mario.limonciello@....com>
> 
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 17 +++++++++++++++++
>>   1 file changed, 17 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/
>> drm/amd/amdgpu/amdgpu_drv.c
>> index 4f8632737574..b24c420983ef 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>> @@ -2541,6 +2541,10 @@ amdgpu_pci_shutdown(struct pci_dev *pdev)
>>       if (amdgpu_ras_intr_triggered())
>>           return;
>>   +    /* device maybe not resumed here, return immediately in this
>> case */
>> +    if (adev->in_s4 && adev->in_suspend)
>> +        return;
>> +
>>       /* if we are running in a VM, make sure the device
>>        * torn down properly on reboot/shutdown.
>>        * unfortunately we can't detect certain
>> @@ -2557,6 +2561,10 @@ static int amdgpu_pmops_prepare(struct device
>> *dev)
>>       struct drm_device *drm_dev = dev_get_drvdata(dev);
>>       struct amdgpu_device *adev = drm_to_adev(drm_dev);
>>   +    /* device maybe not resumed here, return immediately in this
>> case */
>> +    if (adev->in_s4 && adev->in_suspend)
>> +        return 0;
>> +
> 
> Is this one right?  Don't we still want to call prepare() for all the HW
> IP blocks?  The eviction call that happens in prepare() is a no-op but
> there are other IP blocks with an prepare_suspend() callback like DCN.
> 
> That is I think you're destroying the optimization from commit
> 50e0bae34fa6b ("drm/amd/display: Add and use new dm_prepare_suspend()
> callback") by adding this code here.
> 

I guess this takes care of the prepare() before a power_off(). For the
hibernate prepare() call, in_suspend flag will remain false and it
should get executed. If the device is runtime-suspended already, then
the path won't be taken. Assuming that's fine.

Thanks,
Lijo

> 
>>       /* Return a positive number here so
>>        * DPM_FLAG_SMART_SUSPEND works properly
>>        */
>> @@ -2655,12 +2663,21 @@ static int amdgpu_pmops_thaw(struct device *dev)
>>   {
>>       struct drm_device *drm_dev = dev_get_drvdata(dev);
>>   +    /* do not resume device if it's normal hibernation */
>> +    if (!pm_hibernate_is_recovering())
>> +        return 0;
>> +
>>       return amdgpu_device_resume(drm_dev, true);
>>   }
>>     static int amdgpu_pmops_poweroff(struct device *dev)
>>   {
>>       struct drm_device *drm_dev = dev_get_drvdata(dev);
>> +    struct amdgpu_device *adev = drm_to_adev(drm_dev);
>> +
>> +    /* device maybe not resumed here, return immediately in this case */
>> +    if (adev->in_s4 && adev->in_suspend)
>> +        return 0;
>>         return amdgpu_device_suspend(drm_dev, true);
>>   }
>