Re: [PATCH] drm/radeon: Add RADEON_GEM_CPU_ACCESS BO creation flag

["Christian König" <deathsimple@vodafone.de>]

Am 28.08.2014 um 08:56 schrieb Michel Dänzer:
> From: Michel Dänzer <michel.daenzer@amd.com>
>
> This flag is a hint that userspace expects the BO to be accessed by the
> CPU. We can use that hint to prevent such BOs from ever being stored in
> the CPU inaccessible part of VRAM.
>
> Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>

This patch is Reviewed-by: Christian König <christian.koenig@amd.com>

I think we need a similar negative flags as well, e.g. 
RADEON_GEM_NO_CPU_ACCESS.

This way we can stop forcing buffers into the visible VRAM while pinning 
them for scanout.

Regards,
Christian.

> ---
>   drivers/gpu/drm/radeon/radeon_object.c | 11 +++++++++--
>   include/uapi/drm/radeon_drm.h          |  2 ++
>   2 files changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_object.c b/drivers/gpu/drm/radeon/radeon_object.c
> index dc74cc5..908ea541 100644
> --- a/drivers/gpu/drm/radeon/radeon_object.c
> +++ b/drivers/gpu/drm/radeon/radeon_object.c
> @@ -143,7 +143,12 @@ void radeon_ttm_placement_from_domain(struct radeon_bo *rbo, u32 domain)
>   
>   	for (i = 0; i < c; ++i) {
>   		rbo->placements[i].fpfn = 0;
> -		rbo->placements[i].lpfn = 0;
> +		if ((rbo->flags & RADEON_GEM_CPU_ACCESS) &&
> +		    (rbo->placements[i].flags & TTM_PL_FLAG_VRAM))
> +			rbo->placements[i].lpfn =
> +				rbo->rdev->mc.visible_vram_size >> PAGE_SHIFT;
> +		else
> +			rbo->placements[i].lpfn = 0;
>   	}
>   
>   	/*
> @@ -151,7 +156,9 @@ void radeon_ttm_placement_from_domain(struct radeon_bo *rbo, u32 domain)
>   	 * improve fragmentation quality.
>   	 * 512kb was measured as the most optimal number.
>   	 */
> -	if (rbo->tbo.mem.size > 512 * 1024) {
> +	if (!((rbo->flags & RADEON_GEM_CPU_ACCESS) &&
> +	      (rbo->placements[i].flags & TTM_PL_FLAG_VRAM)) &&
> +	    rbo->tbo.mem.size > 512 * 1024) {
>   		for (i = 0; i < c; i++) {
>   			rbo->placements[i].flags |= TTM_PL_FLAG_TOPDOWN;
>   		}
> diff --git a/include/uapi/drm/radeon_drm.h b/include/uapi/drm/radeon_drm.h
> index 509b2d7..bf0067b 100644
> --- a/include/uapi/drm/radeon_drm.h
> +++ b/include/uapi/drm/radeon_drm.h
> @@ -799,6 +799,8 @@ struct drm_radeon_gem_info {
>   #define RADEON_GEM_NO_BACKING_STORE	(1 << 0)
>   #define RADEON_GEM_GTT_UC		(1 << 1)
>   #define RADEON_GEM_GTT_WC		(1 << 2)
> +/* BO is expected to be accessed by the CPU */
> +#define RADEON_GEM_CPU_ACCESS		(1 << 3)
>   
>   struct drm_radeon_gem_create {
>   	uint64_t	size;

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