linux-kernel - Re: [PATCH 3/4] drm/panfrost: Implement ability to turn on/off regulators in suspend

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Message-ID: <85cc1cae-7135-4118-b70a-96eb8d3f0842@collabora.com>
Date:   Tue, 31 Oct 2023 10:00:18 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Steven Price <steven.price@....com>, boris.brezillon@...labora.com
Cc:     robh@...nel.org, maarten.lankhorst@...ux.intel.com,
        mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com,
        daniel@...ll.ch, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, wenst@...omium.org,
        kernel@...labora.com
Subject: Re: [PATCH 3/4] drm/panfrost: Implement ability to turn on/off
 regulators in suspend

Il 30/10/23 15:57, Steven Price ha scritto:
> On 30/10/2023 13:22, AngeloGioacchino Del Regno wrote:
>> Some platforms/SoCs can power off the GPU entirely by completely cutting
>> off power, greatly enhancing battery time during system suspend: add a
>> new pm_feature GPU_PM_VREG_OFF to allow turning off the GPU regulators
>> during full suspend only on selected platforms.
>>
>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
>> ---
>>   drivers/gpu/drm/panfrost/panfrost_device.c | 19 ++++++++++++++++++-
>>   drivers/gpu/drm/panfrost/panfrost_device.h |  2 ++
>>   2 files changed, 20 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c
>> index 2022ed76a620..51b22eb0971d 100644
>> --- a/drivers/gpu/drm/panfrost/panfrost_device.c
>> +++ b/drivers/gpu/drm/panfrost/panfrost_device.c
>> @@ -431,10 +431,21 @@ static int panfrost_device_resume(struct device *dev)
>>   	struct panfrost_device *pfdev = dev_get_drvdata(dev);
>>   	int ret;
>>   
>> +	if (pfdev->comp->pm_features & BIT(GPU_PM_VREG_OFF)) {
>> +		unsigned long freq = pfdev->pfdevfreq.fast_rate;
>> +		struct dev_pm_opp *opp;
>> +
>> +		opp = dev_pm_opp_find_freq_ceil(dev, &freq);
>> +		if (IS_ERR(opp))
>> +			return PTR_ERR(opp);
>> +		dev_pm_opp_put(opp);
>> +		dev_pm_opp_set_opp(dev, opp);
> 
> These lines look the wrong way round - surely we want to hang onto the
> reference until the set_opp call is made?
> 

Whoops! Yes, thanks, this happened during a cleanup for whatever reason.
I'll invert those for v2.

Angelo

> Steve
> 
>> +	}
>> +
>>   	if (pfdev->comp->pm_features & BIT(GPU_PM_CLK_DIS)) {
>>   		ret = clk_enable(pfdev->clock);
>>   		if (ret)
>> -			return ret;
>> +			goto err_clk;
>>   
>>   		if (pfdev->bus_clock) {
>>   			ret = clk_enable(pfdev->bus_clock);
>> @@ -455,6 +466,9 @@ static int panfrost_device_resume(struct device *dev)
>>   err_bus_clk:
>>   	if (pfdev->comp->pm_features & BIT(GPU_PM_CLK_DIS))
>>   		clk_disable(pfdev->clock);
>> +err_clk:
>> +	if (pfdev->comp->pm_features & BIT(GPU_PM_VREG_OFF))
>> +		dev_pm_opp_set_opp(dev, NULL);
>>   	return ret;
>>   }
>>   
>> @@ -474,6 +488,9 @@ static int panfrost_device_suspend(struct device *dev)
>>   			clk_disable(pfdev->bus_clock);
>>   	}
>>   
>> +	if (pfdev->comp->pm_features & BIT(GPU_PM_VREG_OFF))
>> +		dev_pm_opp_set_opp(dev, NULL);
>> +
>>   	return 0;
>>   }
>>   
>> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
>> index d7f179eb8ea3..0fc558db6bfd 100644
>> --- a/drivers/gpu/drm/panfrost/panfrost_device.h
>> +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
>> @@ -28,9 +28,11 @@ struct panfrost_perfcnt;
>>   /**
>>    * enum panfrost_gpu_pm - Supported kernel power management features
>>    * @GPU_PM_CLK_DIS:  Allow disabling clocks during system suspend
>> + * @GPU_PM_VREG_OFF: Allow turning off regulators during system suspend
>>    */
>>   enum panfrost_gpu_pm {
>>   	GPU_PM_CLK_DIS,
>> +	GPU_PM_VREG_OFF,
>>   };
>>   
>>   struct panfrost_features {
> 
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