On 02/11/2023 14:26, AngeloGioacchino Del Regno 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)
> resulting in a full system lockup.
>
> Doing this only for full system sleep never showed issues during my
> testing by suspending and resuming the system continuously for more
> than 100 cycles.
>
> Signed-off-by: AngeloGioacchino Del Regno
> <angelogioacchino.delre...@collabora.com>
> ---
>
> Note: Even after fixing the panfrost_power_off() function, I'm still
> getting issues with turning off the clocks at .runtime_suspend() but
> this time, instead of getting a GPU lockup, the entire SoC will deadlock
> bringing down the entire system with it (so it's even worst!) :-)
Ouch! Hopefully that's a SoC issue as I can't see anything that should
cause problems. But note that if the GPU is powered down during a bus
transaction that can lock up the entire bus.
>
>
> 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);
NIT: I would normally expect panfrost_device_resume() to have the
opposite order. I'm not sure if there's an expected order here but I
feel like the bus should be enabled before core - so _resume() would
need to be swapped round.
Other than that:
Reviewed-by: Steven Price <steven.pr...@arm.com>
Thanks,
Steve
> + }
> +
> + 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;
> };
>
> struct panfrost_device {
