[PATCH] drm/panthor: Fix handling of partial GPU mapping of BOs

[Akash Goel]

This commit fixes the handling of partial GPU mapping of buffer objects
in Panthor.
VM_BIND ioctl allows Userspace to partially map the BOs to GPU.
To map a BO, Panthor walks through the sg_table to retrieve the physical
address of pages. If the mapping is created at an offset into the BO,
then the scatterlist(s) at the beginning have to be skipped to reach the
one corresponding to the offset. But the case where the offset didn't
point to the first page of desired scatterlist wasn't handled correctly.
The bug caused the partial GPU mapping of BO to go wrong for the said
case, as the pages didn't get map at the expected virtual address and
consequently there were kernel warnings on unmap.

Signed-off-by: Akash Goel <akash.goel at arm.com>
---
 drivers/gpu/drm/panthor/panthor_mmu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index d8cc9e7d064e..6bc188d9a9ad 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -957,6 +957,7 @@ panthor_vm_map_pages(struct panthor_vm *vm, u64 iova, int prot,
 
 		paddr += offset;
 		len -= offset;
+		offset = 0;
 		len = min_t(size_t, len, size);
 		size -= len;
 
-- 
2.25.1