Re: [PATCH 3/4] drm/nouveau: hook up cache sync functions

[Lucas Stach <l.stach-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]

Am Montag, den 19.05.2014, 16:10 +0900 schrieb Alexandre Courbot:
> From: Lucas Stach <dev-8ppwABl0HbeELgA04lAiVw@public.gmane.org>
> 
> Signed-off-by: Lucas Stach <dev-8ppwABl0HbeELgA04lAiVw@public.gmane.org>
> [acourbot-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org: make conditional and platform-friendly]
> Signed-off-by: Alexandre Courbot <acourbot-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> ---
>  drivers/gpu/drm/nouveau/nouveau_bo.c  | 32 ++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/nouveau/nouveau_bo.h  | 20 ++++++++++++++++++++
>  drivers/gpu/drm/nouveau/nouveau_gem.c |  8 +++++++-
>  3 files changed, 59 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
> index b6dc85c614be..0886f47e5244 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_bo.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
> @@ -407,6 +407,8 @@ nouveau_bo_validate(struct nouveau_bo *nvbo, bool interruptible,
>  {
>  	int ret;
>  
> +	nouveau_bo_sync_for_device(nvbo);
> +
>  	ret = ttm_bo_validate(&nvbo->bo, &nvbo->placement,
>  			      interruptible, no_wait_gpu);
>  	if (ret)
> @@ -487,6 +489,36 @@ nouveau_bo_invalidate_caches(struct ttm_bo_device *bdev, uint32_t flags)
>  	return 0;
>  }
>  
> +#ifdef NOUVEAU_NEED_CACHE_SYNC

I don't like this ifdef at all. I know calling this functions will add a
little overhead to x86 where it isn't strictly required, but I think
it's negligible.

When I looked at them the dma_sync_single_for_[device|cpu] functions
which are called here map out to just a drain of the PCI store buffer on
x86, which should be fast enough to be done unconditionally. They won't
so any time-consuming cache synchronization on PCI coherent arches.

Regards,
Lucas

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