From f352262f727215553879705bacbcb208979f3eff Mon Sep 17 00:00:00 2001 From: Robin Murphy Date: Tue, 8 Nov 2022 17:06:19 +0000 Subject: drm/panfrost: Split io-pgtable requests properly 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 Signed-off-by: Robin Murphy Tested-by: Dmitry Osipenko Reviewed-by: Steven Price Signed-off-by: Steven Price Link: https://patchwork.freedesktop.org/patch/msgid/49e54bb4019cd06e01549b106d7ac37c3d182cd3.1667927179.git.robin.murphy@arm.com --- drivers/gpu/drm/panfrost/panfrost_mmu.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'drivers/gpu/drm/panfrost/panfrost_mmu.c') diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c index e246d914e7f6..4e83a1891f3e 100644 --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c @@ -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; } -- cgit