Re: [PATCH] drm/xe: handle flat ccs during hibernation on igpu

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Tue, Nov 12, 2024 at 04:28:28PM +0000, Matthew Auld wrote:
> Starting from LNL, CCS has moved over to flat CCS model where there is
> now dedicated memory reserved for storing compression state. On
> platforms like LNL this reserved memory lives inside graphics stolen
> memory, which is not treated like normal RAM and is therefore skipped by
> the core kernel when creating the hibernation image. Currently if
> something was compressed and we enter hibernation all the corresponding
> CCS state is lost on such HW, resulting in corrupted memory. To fix this
> evict user buffers from TT -> SYSTEM to ensure we take a snapshot of the
> raw CCS state when entering hibernation, where upon resuming we can
> restore the raw CCS state back when next validating the buffer. This has
> been confirmed to fix display corruption on LNL when coming back from
> hibernation.
> 
> Fixes: cbdc52c11c9b ("drm/xe/xe2: Support flat ccs")
> Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/3409
> Signed-off-by: Matthew Auld <matthew.auld@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: <stable@vger.kernel.org> # v6.8+
> ---
>  drivers/gpu/drm/xe/xe_bo_evict.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_bo_evict.c b/drivers/gpu/drm/xe/xe_bo_evict.c
> index b01bc20eb90b..8fb2be061003 100644
> --- a/drivers/gpu/drm/xe/xe_bo_evict.c
> +++ b/drivers/gpu/drm/xe/xe_bo_evict.c
> @@ -35,10 +35,21 @@ int xe_bo_evict_all(struct xe_device *xe)
>  	int ret;
>  
>  	/* User memory */
> -	for (mem_type = XE_PL_VRAM0; mem_type <= XE_PL_VRAM1; ++mem_type) {
> +	for (mem_type = XE_PL_TT; mem_type <= XE_PL_VRAM1; ++mem_type) {
>  		struct ttm_resource_manager *man =
>  			ttm_manager_type(bdev, mem_type);
>  
> +		/*
> +		 * On igpu platforms with flat CCS we need to ensure we save and restore any CCS
> +		 * state since this state lives inside graphics stolen memory which doesn't survive
> +		 * hibernation.
> +		 *
> +		 * This can be further improved by only evicting objects that we know have actually
> +		 * used a compression enabled PAT index.

yeap, but for now let's keep it simple...


Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>


> +		 */
> +		if (mem_type == XE_PL_TT && (IS_DGFX(xe) || !xe_device_has_flat_ccs(xe)))
> +			continue;
> +
>  		if (man) {
>  			ret = ttm_resource_manager_evict_all(bdev, man);
>  			if (ret)
> -- 
> 2.47.0
>