All of the MediaTek SoCs supported by Panfrost can completely cut power
to the GPU during full system sleep without any user-noticeable delay
in the resume operation, as shown by measurements taken on multiple
MediaTek SoCs (MT8183/86/92/95).

As an example, for MT8195 - a "before" with only runtime PM operations
(so, without turning on/off regulators), and an "after" executing both
the system sleep .resume() handler and .runtime_resume() (so the time
refers to T_Resume + T_Runtime_Resume):

Average Panfrost-only system sleep resume time, before: ~33500ns
Average Panfrost-only system sleep resume time, after:  ~336200ns

Keep in mind that this additional ~308200 nanoseconds delay happens only
in resume from a full system suspend, and not in runtime PM operations,
hence it is acceptable.

Measurements were also taken on MT8186, showing a delay of ~312000 ns.

Testing of this happened on all of the aforementioned MediaTek SoCs, but:
MT8183 got tested only by KernelCI with <=10 suspend/resume cycles
MT8186, MT8192, MT8195 were tested manually with over 100 suspend/resume
cycles with GNOME DE (Mutter + Wayland).

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
---
 drivers/gpu/drm/panfrost/panfrost_drv.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
index 82f3c5fe9c58..f63382d9ab04 100644
--- a/drivers/gpu/drm/panfrost/panfrost_drv.c
+++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
@@ -734,7 +734,7 @@ static const struct panfrost_compatible mediatek_mt8183_b_data = {
 	.supply_names = mediatek_mt8183_b_supplies,
 	.num_pm_domains = ARRAY_SIZE(mediatek_mt8183_pm_domains),
 	.pm_domain_names = mediatek_mt8183_pm_domains,
-	.pm_features = BIT(GPU_PM_CLK_DIS),
+	.pm_features = BIT(GPU_PM_CLK_DIS) | BIT(GPU_PM_VREG_OFF),
 };
 
 static const char * const mediatek_mt8186_pm_domains[] = { "core0", "core1" };
@@ -743,7 +743,7 @@ static const struct panfrost_compatible mediatek_mt8186_data = {
 	.supply_names = mediatek_mt8183_b_supplies,
 	.num_pm_domains = ARRAY_SIZE(mediatek_mt8186_pm_domains),
 	.pm_domain_names = mediatek_mt8186_pm_domains,
-	.pm_features = BIT(GPU_PM_CLK_DIS),
+	.pm_features = BIT(GPU_PM_CLK_DIS) | BIT(GPU_PM_VREG_OFF),
 };
 
 static const char * const mediatek_mt8192_supplies[] = { "mali", NULL };
@@ -754,7 +754,7 @@ static const struct panfrost_compatible mediatek_mt8192_data = {
 	.supply_names = mediatek_mt8192_supplies,
 	.num_pm_domains = ARRAY_SIZE(mediatek_mt8192_pm_domains),
 	.pm_domain_names = mediatek_mt8192_pm_domains,
-	.pm_features = BIT(GPU_PM_CLK_DIS),
+	.pm_features = BIT(GPU_PM_CLK_DIS) | BIT(GPU_PM_VREG_OFF),
 };
 
 static const struct of_device_id dt_match[] = {
-- 
2.42.0

On 09/11/2023 10:25, AngeloGioacchino Del Regno wrote:
> All of the MediaTek SoCs supported by Panfrost can completely cut power
> to the GPU during full system sleep without any user-noticeable delay
> in the resume operation, as shown by measurements taken on multiple
> MediaTek SoCs (MT8183/86/92/95).
> 
> As an example, for MT8195 - a "before" with only runtime PM operations
> (so, without turning on/off regulators), and an "after" executing both
> the system sleep .resume() handler and .runtime_resume() (so the time
> refers to T_Resume + T_Runtime_Resume):
> 
> Average Panfrost-only system sleep resume time, before: ~33500ns
> Average Panfrost-only system sleep resume time, after:  ~336200ns
> 
> Keep in mind that this additional ~308200 nanoseconds delay happens only
> in resume from a full system suspend, and not in runtime PM operations,
> hence it is acceptable.
> 
> Measurements were also taken on MT8186, showing a delay of ~312000 ns.
> 
> Testing of this happened on all of the aforementioned MediaTek SoCs, but:
> MT8183 got tested only by KernelCI with <=10 suspend/resume cycles
> MT8186, MT8192, MT8195 were tested manually with over 100 suspend/resume
> cycles with GNOME DE (Mutter + Wayland).
> 
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Reviewed-by: Steven Price <steven.price@arm.com>

> ---
>  drivers/gpu/drm/panfrost/panfrost_drv.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> index 82f3c5fe9c58..f63382d9ab04 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> @@ -734,7 +734,7 @@ static const struct panfrost_compatible mediatek_mt8183_b_data = {
>  	.supply_names = mediatek_mt8183_b_supplies,
>  	.num_pm_domains = ARRAY_SIZE(mediatek_mt8183_pm_domains),
>  	.pm_domain_names = mediatek_mt8183_pm_domains,
> -	.pm_features = BIT(GPU_PM_CLK_DIS),
> +	.pm_features = BIT(GPU_PM_CLK_DIS) | BIT(GPU_PM_VREG_OFF),
>  };
>  
>  static const char * const mediatek_mt8186_pm_domains[] = { "core0", "core1" };
> @@ -743,7 +743,7 @@ static const struct panfrost_compatible mediatek_mt8186_data = {
>  	.supply_names = mediatek_mt8183_b_supplies,
>  	.num_pm_domains = ARRAY_SIZE(mediatek_mt8186_pm_domains),
>  	.pm_domain_names = mediatek_mt8186_pm_domains,
> -	.pm_features = BIT(GPU_PM_CLK_DIS),
> +	.pm_features = BIT(GPU_PM_CLK_DIS) | BIT(GPU_PM_VREG_OFF),
>  };
>  
>  static const char * const mediatek_mt8192_supplies[] = { "mali", NULL };
> @@ -754,7 +754,7 @@ static const struct panfrost_compatible mediatek_mt8192_data = {
>  	.supply_names = mediatek_mt8192_supplies,
>  	.num_pm_domains = ARRAY_SIZE(mediatek_mt8192_pm_domains),
>  	.pm_domain_names = mediatek_mt8192_pm_domains,
> -	.pm_features = BIT(GPU_PM_CLK_DIS),
> +	.pm_features = BIT(GPU_PM_CLK_DIS) | BIT(GPU_PM_VREG_OFF),
>  };
>  
>  static const struct of_device_id dt_match[] = {