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drm/panfrost: Split io-pgtable requests properly

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Although we don't use 1GB block mappings, we still need to split
map/unmap requests at 1GB boundaries to match what io-pgtable expects.
Fix that, and add some explanation to make sense of it all.

Fixes: 3740b081795a ("drm/panfrost: Update io-pgtable API")
Reported-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/49e54bb4019cd06e01549b106d7ac37c3d182cd3.1667927179.git.robin.murphy@arm.com
This commit is contained in:
Robin Murphy 2022-11-08 17:06:19 +00:00 committed by Steven Price
parent e0b26b9482
commit f352262f72
1 changed files with 10 additions and 1 deletions
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11
drivers/gpu/drm/panfrost/panfrost_mmu.c
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@ -250,13 +250,22 @@ void panfrost_mmu_reset(struct panfrost_device *pfdev)
static size_t get_pgsize(u64 addr, size_t size, size_t *count)
{
/*
* io-pgtable only operates on multiple pages within a single table
* entry, so we need to split at boundaries of the table size, i.e.
* the next block size up. The distance from address A to the next
* boundary of block size B is logically B - A % B, but in unsigned
* two's complement where B is a power of two we get the equivalence
* B - A % B == (B - A) % B == (n * B - A) % B, and choose n = 0 :)
*/
size_t blk_offset = -addr % SZ_2M;
if (blk_offset || size < SZ_2M) {
*count = min_not_zero(blk_offset, size) / SZ_4K;
return SZ_4K;
}
*count = size / SZ_2M;
blk_offset = -addr % SZ_1G ?: SZ_1G;
*count = min(blk_offset, size) / SZ_2M;
return SZ_2M;
}