Commit 3546fb0c authored Dec 12, 2016 by Lucas Stach

drm/etnaviv: trick drm_mm into giving out a low IOVA

After rollover of the IOVA space, we want to get a low IOVA address,
otherwise the the games we play by remembering the last IOVA are
pointless. When we search for a free hole with DRM_MM_SEARCH_DEFAULT,
drm_mm will pop the next entry from the free holes stack, which will
likely be a high IOVA. By using DRM_MM_SEARCH_BELOW we can trick
drm_mm into reversing the search and provide us with a low IOVA.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Wladimir van der Laan <laanwj@gmail.com>

parent 7ce7d89f

drivers/gpu/drm/etnaviv/etnaviv_mmu.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -116,9 +116,14 @@ static int etnaviv_iommu_find_iova(struct etnaviv_iommu *mmu,
		struct list_head list;
		bool found;

		/*
		* XXX: The DRM_MM_SEARCH_BELOW is really a hack to trick
		* drm_mm into giving out a low IOVA after address space
		* rollover. This needs a proper fix.
		*/
		ret = drm_mm_insert_node_in_range(&mmu->mm, node,
		size, 0, mmu->last_iova, ~0UL,
		DRM_MM_SEARCH_DEFAULT);
		mmu->last_iova ? DRM_MM_SEARCH_DEFAULT : DRM_MM_SEARCH_BELOW);

		if (ret != -ENOSPC)
		break;