[PATCH 1/3] drm/xe/vf: Don't check has flat ccs in bios on VF

[Matt Roper]

On Wed, Dec 11, 2024 at 07:42:09AM +0100, Marcin Bernatowicz wrote:
> From: Jakub Kolakowski <jakub1.kolakowski at intel.com>
> 
> Don't check for flat ccs from VF-level as VF does not have direct
> access to the register.
> 
> If the BIOS disables FlatCCS support (a use-case that will nearly never
> be used) and the has_flat_ccs flag is set, there shouldn't be
> any functional impact. The hardware will drop writes to the CCS region,
> and reads from the CCS region will always return 0.
> For the native case, the flag is disabled if the BIOS disables
> it to avoid unnecessary overhead in buffer object (BO) creation
> and migration.
> 
> Signed-off-by: Jakub Kolakowski <jakub1.kolakowski at intel.com>
> Suggested-by: Piotr Piórkowski <piotr.piorkowski at intel.com>
> Cc: Adam Miszczak <adam.miszczak at linux.intel.com>
> Cc: Jakub Kolakowski <jakub1.kolakowski at intel.com>
> Cc: Lukasz Laguna <lukasz.laguna at intel.com>
> Cc: Marcin Bernatowicz <marcin.bernatowicz at linux.intel.com>
> Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
> Cc: Michal Winiarski <michal.winiarski at intel.com>
> Cc: Narasimha C V <narasimha.c.v at intel.com>
> Cc: Piotr Piorkowski <piotr.piorkowski at intel.com>
> Cc: Satyanarayana K V P <satyanarayana.k.v.p at intel.com>
> Cc: Tomasz Lis <tomasz.lis at intel.com>
> Cc: Matt Roper <matthew.d.roper at intel.com>
> Signed-off-by: Marcin Bernatowicz <marcin.bernatowicz at linux.intel.com>

Reviewed-by: Matt Roper <matthew.d.roper at intel.com>

> ---
>  drivers/gpu/drm/xe/xe_device.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
> index 56d4ffb650da..ec0ea9c914b4 100644
> --- a/drivers/gpu/drm/xe/xe_device.c
> +++ b/drivers/gpu/drm/xe/xe_device.c
> @@ -604,7 +604,7 @@ static int probe_has_flat_ccs(struct xe_device *xe)
>  	u32 reg;
>  
>  	/* Always enabled/disabled, no runtime check to do */
> -	if (GRAPHICS_VER(xe) < 20 || !xe->info.has_flat_ccs)
> +	if (GRAPHICS_VER(xe) < 20 || !xe->info.has_flat_ccs || IS_SRIOV_VF(xe))
>  		return 0;
>  
>  	gt = xe_root_mmio_gt(xe);
> -- 
> 2.31.1
> 

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