[PATCH v2 2/2] drm/imagination: Size page table preallocation by device address

[Gyeyoung Baek]

Commit 0a8224058a58 ("drm/imagination: Fix page count for page table for
map() interface") passed the device address to
pvr_mmu_op_context_create(), but the preallocation is still sized from
device_addr + sgt_offset with an exclusive end. The offset into the
object's pages has no place in a device-virtual range, and the exclusive
end allocates one table too many when the range ends on a table
boundary.

Count the tables from device_addr and the inclusive end of the range.

Fixes: 0a8224058a58 ("drm/imagination: Fix page count for page table for map() interface")
Fixes: ff5f643de0bf ("drm/imagination: Add GEM and VM related code")
Signed-off-by: Gyeyoung Baek <gye976@xxxxxxxxx>
---
 drivers/gpu/drm/imagination/pvr_mmu.c | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/imagination/pvr_mmu.c b/drivers/gpu/drm/imagination/pvr_mmu.c
index 62eae7fcd5a..67e73d7d5d0 100644
--- a/drivers/gpu/drm/imagination/pvr_mmu.c
+++ b/drivers/gpu/drm/imagination/pvr_mmu.c
@@ -2337,7 +2337,7 @@ void pvr_mmu_op_context_destroy(struct pvr_mmu_op_context *op_ctx)
  * @ctx: MMU context associated with owning VM context.
  * @sgt: Scatter gather table containing pages pinned for use by this context.
  * @device_addr: Virtual device address at the start of the requested mapping.
- * @sgt_offset: Start offset of the requested device-virtual memory mapping.
+ * @sgt_offset: Offset into @sgt of the start of the requested mapping.
  * @size: Size in bytes of the requested device-virtual memory mapping. For an
  * unmapping, this should be zero so that no page tables are allocated.
  *
@@ -2350,7 +2350,6 @@ struct pvr_mmu_op_context *
 pvr_mmu_op_context_create(struct pvr_mmu_context *ctx, struct sg_table *sgt,
 			  u64 device_addr, u64 sgt_offset, u64 size)
 {
-	u64 start_addr = device_addr + sgt_offset;
 	int err;
 
 	struct pvr_mmu_op_context *op_ctx = kzalloc_obj(*op_ctx);
@@ -2365,18 +2364,18 @@ pvr_mmu_op_context_create(struct pvr_mmu_context *ctx, struct sg_table *sgt,
 
 	if (size) {
 		/*
-		 * The number of page table objects we need to prealloc is
-		 * indicated by the mapping size, start address and the sizes
-		 * of the areas mapped per PT or PD. The range calculation is
-		 * identical to that for the index into a table for a device
-		 * address, so we reuse those functions here.
+		 * The page tables needed are set by the device-virtual range
+		 * being mapped: one level 1 table per 1GiB region and one
+		 * level 0 table per 2MiB region the range touches. Tables that
+		 * already exist are not consumed, so this is an upper bound.
 		 */
-		const u32 l1_start_idx = pvr_page_table_l2_idx(start_addr);
-		const u32 l1_end_idx = pvr_page_table_l2_idx(start_addr + size);
-		const u32 l1_count = l1_end_idx - l1_start_idx + 1;
-		const u32 l0_start_idx = pvr_page_table_l1_idx(start_addr);
-		const u32 l0_end_idx = pvr_page_table_l1_idx(start_addr + size);
-		const u32 l0_count = l0_end_idx - l0_start_idx + 1;
+		const u64 last_addr = device_addr + size - 1;
+		const u64 l1_count =
+			(last_addr >> ROGUE_MMUCTRL_VADDR_PC_INDEX_SHIFT) -
+			(device_addr >> ROGUE_MMUCTRL_VADDR_PC_INDEX_SHIFT) + 1;
+		const u64 l0_count =
+			(last_addr >> ROGUE_MMUCTRL_VADDR_PD_INDEX_SHIFT) -
+			(device_addr >> ROGUE_MMUCTRL_VADDR_PD_INDEX_SHIFT) + 1;
 
 		/*
 		 * Alloc and push page table entries until we have enough of

-- 
2.43.0