From: Lucas Stach Date: Thu, 30 Nov 2017 17:34:28 +0000 (+0100) Subject: drm/prime: skip CPU sync in map/unmap dma_buf X-Git-Tag: v4.16-rc1~96^2~28^2~40 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=ca0e68e21aae;p=linux.git drm/prime: skip CPU sync in map/unmap dma_buf Dma-bufs should already be device coherent, as they are only pulled in the CPU domain via the begin/end cpu_access calls. As we cache the mapping set up by dma_map_sg a CPU sync at this point will not actually guarantee proper coherency on non-coherent architectures, so we can as well stop pretending. This is an important performance fix for architectures which need explicit cache synchronization and userspace doing lots of dma-buf imports. Improves Weston on Etnaviv performance 5x, where before this patch > 90% of Weston CPU time was spent synchronizing caches for buffers which are already device coherent. Signed-off-by: Lucas Stach Reviewed-by: Chris Wilson Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20171130173428.8666-1-l.stach@pengutronix.de --- diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c index 8de93a226c24..9a17725b0f7a 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -218,8 +218,9 @@ static void drm_gem_map_detach(struct dma_buf *dma_buf, sgt = prime_attach->sgt; if (sgt) { if (prime_attach->dir != DMA_NONE) - dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents, - prime_attach->dir); + dma_unmap_sg_attrs(attach->dev, sgt->sgl, sgt->nents, + prime_attach->dir, + DMA_ATTR_SKIP_CPU_SYNC); sg_free_table(sgt); } @@ -277,7 +278,8 @@ static struct sg_table *drm_gem_map_dma_buf(struct dma_buf_attachment *attach, sgt = obj->dev->driver->gem_prime_get_sg_table(obj); if (!IS_ERR(sgt)) { - if (!dma_map_sg(attach->dev, sgt->sgl, sgt->nents, dir)) { + if (!dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir, + DMA_ATTR_SKIP_CPU_SYNC)) { sg_free_table(sgt); kfree(sgt); sgt = ERR_PTR(-ENOMEM);