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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>
This commit is contained in:
Lucas Stach 2016-12-12 16:15:17 +01:00
parent 7ce7d89f48
commit 3546fb0cda
1 changed files with 6 additions and 1 deletions
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7
drivers/gpu/drm/etnaviv/etnaviv_mmu.c
View File

@ -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;