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Message-ID: <CAGXv+5EhRUz6qptSzhzbcq4-qQKDzN5xFtS0WMNUCOH5JSL0Jw@mail.gmail.com>
Date: Tue, 31 Oct 2023 11:18:46 +0800
From: Chen-Yu Tsai <wenst@...omium.org>
To: AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com>
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
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).
ChenYu
> };
>
> struct panfrost_device {
> --
> 2.42.0
>
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