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Message-ID: <38b62659-dcef-4b49-9b4c-e055ed9a215a@collabora.com>
Date: Tue, 31 Oct 2023 14:20:39 +0100
From: AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com>
To: Chen-Yu Tsai <wenst@...omium.org>
Cc: boris.brezillon@...labora.com, robh@...nel.org,
steven.price@....com, 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, kernel@...labora.com
Subject: Re: [PATCH 1/4] drm/panfrost: Implement ability to turn on/off GPU
clocks in suspend
Il 31/10/23 04:18, Chen-Yu Tsai ha scritto:
> On Mon, Oct 30, 2023 at 9:23 PM AngeloGioacchino Del Regno
> <angelogioacchino.delregno@...labora.com> wrote:
>>
>> Currently, the GPU is being internally powered off for runtime suspend
>> and turned back on for runtime resume through commands sent to it, but
>> note that the GPU doesn't need to be clocked during the poweroff state,
>> hence it is possible to save some power on selected platforms.
>>
>> Add suspend and resume handlers for full system sleep and then add
>> a new panfrost_gpu_pm enumeration and a pm_features variable in the
>> panfrost_compatible structure: BIT(GPU_PM_CLK_DIS) will be used to
>> enable this power saving technique only on SoCs that are able to
>> safely use it.
>>
>> Note that this was implemented only for the system sleep case and not
>> for runtime PM because testing on one of my MediaTek platforms showed
>> issues when turning on and off clocks aggressively (in PM runtime),
>> with the GPU locking up and unable to soft reset, eventually resulting
>> in a full system lockup.
>>
>> Doing this only for full system sleep never showed issues in 3 days
>> of testing by suspending and resuming the system continuously.
>>
>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
>> ---
>> drivers/gpu/drm/panfrost/panfrost_device.c | 61 ++++++++++++++++++++--
>> drivers/gpu/drm/panfrost/panfrost_device.h | 11 ++++
>> 2 files changed, 68 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c
>> index 28f7046e1b1a..2022ed76a620 100644
>> --- a/drivers/gpu/drm/panfrost/panfrost_device.c
>> +++ b/drivers/gpu/drm/panfrost/panfrost_device.c
>> @@ -403,7 +403,7 @@ void panfrost_device_reset(struct panfrost_device *pfdev)
>> panfrost_job_enable_interrupts(pfdev);
>> }
>>
>> -static int panfrost_device_resume(struct device *dev)
>> +static int panfrost_device_runtime_resume(struct device *dev)
>> {
>> struct panfrost_device *pfdev = dev_get_drvdata(dev);
>>
>> @@ -413,7 +413,7 @@ static int panfrost_device_resume(struct device *dev)
>> return 0;
>> }
>>
>> -static int panfrost_device_suspend(struct device *dev)
>> +static int panfrost_device_runtime_suspend(struct device *dev)
>> {
>> struct panfrost_device *pfdev = dev_get_drvdata(dev);
>>
>> @@ -426,5 +426,58 @@ static int panfrost_device_suspend(struct device *dev)
>> return 0;
>> }
>>
>> -EXPORT_GPL_RUNTIME_DEV_PM_OPS(panfrost_pm_ops, panfrost_device_suspend,
>> - panfrost_device_resume, NULL);
>> +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_CLK_DIS)) {
>> + ret = clk_enable(pfdev->clock);
>> + if (ret)
>> + return ret;
>> +
>> + if (pfdev->bus_clock) {
>> + ret = clk_enable(pfdev->bus_clock);
>> + if (ret)
>> + goto err_bus_clk;
>> + }
>> + }
>> +
>> + ret = pm_runtime_force_resume(dev);
>> + if (ret)
>> + goto err_resume;
>> +
>> + return 0;
>> +
>> +err_resume:
>> + if (pfdev->comp->pm_features & BIT(GPU_PM_CLK_DIS) && pfdev->bus_clock)
>> + clk_disable(pfdev->bus_clock);
>> +err_bus_clk:
>> + if (pfdev->comp->pm_features & BIT(GPU_PM_CLK_DIS))
>> + clk_disable(pfdev->clock);
>> + return ret;
>> +}
>> +
>> +static int panfrost_device_suspend(struct device *dev)
>> +{
>> + struct panfrost_device *pfdev = dev_get_drvdata(dev);
>> + int ret;
>> +
>> + ret = pm_runtime_force_suspend(dev);
>> + if (ret)
>> + return ret;
>> +
>> + if (pfdev->comp->pm_features & BIT(GPU_PM_CLK_DIS)) {
>> + clk_disable(pfdev->clock);
>> +
>> + if (pfdev->bus_clock)
>> + clk_disable(pfdev->bus_clock);
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +EXPORT_GPL_DEV_PM_OPS(panfrost_pm_ops) = {
>> + RUNTIME_PM_OPS(panfrost_device_runtime_suspend, panfrost_device_runtime_resume, NULL)
>> + SYSTEM_SLEEP_PM_OPS(panfrost_device_suspend, panfrost_device_resume)
>> +};
>> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
>> index 1ef38f60d5dc..d7f179eb8ea3 100644
>> --- a/drivers/gpu/drm/panfrost/panfrost_device.h
>> +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
>> @@ -25,6 +25,14 @@ struct panfrost_perfcnt;
>> #define NUM_JOB_SLOTS 3
>> #define MAX_PM_DOMAINS 5
>>
>> +/**
>> + * enum panfrost_gpu_pm - Supported kernel power management features
>> + * @GPU_PM_CLK_DIS: Allow disabling clocks during system suspend
>> + */
>> +enum panfrost_gpu_pm {
>> + GPU_PM_CLK_DIS,
>> +};
>> +
>> struct panfrost_features {
>> u16 id;
>> u16 revision;
>> @@ -75,6 +83,9 @@ struct panfrost_compatible {
>>
>> /* Vendor implementation quirks callback */
>> void (*vendor_quirk)(struct panfrost_device *pfdev);
>> +
>> + /* Allowed PM features */
>> + u8 pm_features;
>
> Nit: I'd just use bitfields. They are easier to set and get without
> extra macros, and the naming would be self-explanatory. Unless you
> expect a need to do mask checking (though the compiler might be able
> to optimize this).
>
I don't expect a need to do mask checking, but I don't expect the opposite either..
...this could happen in the future, or maybe not, and this becomes a bool, even.
That's why I went with a u8 :-)
Let's keep it flexible.
Thanks,
Angelo
> ChenYu
>
>> };
>>
>> struct panfrost_device {
>> --
>> 2.42.0
>>
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