[RFC 34/34] drm/xe: Enable D3Cold on 'low' VRAM utilization

[Matthew Auld]

On 26/01/2024 20:30, Rodrigo Vivi wrote:
> Now that we eliminated all the mem_access get/put with its
> locking issues from the inner calls of migration, we can
> allow D3Cold.
> 
> Enable it when VRAM utilization is lower then 300Mb. On
> higher utilization we only allow D3hot so we don't increase
> so much the latency on runtime resume due to the memory
> restoration.

Note that nothing in CI is d3cold capable it seems, so they will never 
trigger this path AFAIK. All platforms return:

[drm:xe_pci_probe [xe]] d3cold: capable=no

Is that a bug, or perhaps there is something else needed? Main question 
is how to get CI test coverage for this here.

> 
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
> ---
>   drivers/gpu/drm/xe/xe_pm.h | 7 +------
>   1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_pm.h b/drivers/gpu/drm/xe/xe_pm.h
> index 0ae4f6a60c6d..bc6bd2a01189 100644
> --- a/drivers/gpu/drm/xe/xe_pm.h
> +++ b/drivers/gpu/drm/xe/xe_pm.h
> @@ -8,12 +8,7 @@
>   
>   #include <linux/pm_runtime.h>
>   
> -/*
> - * TODO: Threshold = 0 will block D3Cold.
> - *       Before we can move this to a higher value (like 300), we need to:
> - *           1. rewrite the VRAM save / restore to avoid buffer object locks
> - */
> -#define DEFAULT_VRAM_THRESHOLD 0 /* in MB */
> +#define DEFAULT_VRAM_THRESHOLD 300 /* in MB */
>   
>   struct xe_device;
>