[PATCH 08/11] drm/xe/xe2hpg: Limit chunk size to 4MiB for vram

[Matt Roper]

On Tue, Apr 02, 2024 at 06:17:21PM +0530, Balasubramani Vivekanandan wrote:
> From: Akshata Jahagirdar <akshata.jahagirdar at intel.com>
> 
> Currently, The maximum chunk size for vram copy is 8 MiB, which means
> flat ccs copy would be able handle 8 MiB/(page_sizes).  Since page size
> for vram is 4k the value will be 2048 pages which won't fit in 10
> bitspace.
> 
> Therefore we need to limit chunk size to 4MiB the way it is for LNL.

I found this explanation a bit hard to follow, you might want to clarify
that it's the XY_CTRL_SURF_COPY_BLT instruction specifically that drives
this limit.  I.e., the change on Xe2 is that the size provided to that
instruction now represents one less than the number of 4K pages of the
main surface for which CCS data needs to be copied.  Since that field is
10-bits, we can only copy CCS data that corresponds to 1024 * 4k.

Although now I'm wondering when we actually wind up needing to copy CCS
data directly on Xe2?  With compression controlled by PAT bits in the
PTE, doesn't the writing of the FlatCCS metadata happen automatically on
all main surface copies (both for compressed and non-compressed
surfaces)?


Matt

> 
> Signed-off-by: Akshata Jahagirdar <akshata.jahagirdar at intel.com>
> Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray at intel.com>
> Signed-off-by: Balasubramani Vivekanandan <balasubramani.vivekanandan at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_migrate.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_migrate.c b/drivers/gpu/drm/xe/xe_migrate.c
> index ee1bb938c493..07a09649787d 100644
> --- a/drivers/gpu/drm/xe/xe_migrate.c
> +++ b/drivers/gpu/drm/xe/xe_migrate.c
> @@ -407,7 +407,7 @@ struct xe_migrate *xe_migrate_init(struct xe_tile *tile)
>  
>  static u64 max_mem_transfer_per_pass(struct xe_device *xe)
>  {
> -	if (!IS_DGFX(xe) && xe_device_has_flat_ccs(xe))
> +	if (GRAPHICS_VER(xe) >= 20 && xe_device_has_flat_ccs(xe))
>  		return MAX_CCS_LIMITED_TRANSFER;
>  
>  	return MAX_PREEMPTDISABLE_TRANSFER;
> -- 
> 2.25.1
> 

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation