drm/xe/migrate: Cap PTEs written by MI_STORE_DATA_IMM to 510

Although MI_STORE_DATA_IMM's "length" field is 10-bits, 0x3FE is
considered the largest legal value accepted.  Since that instruction
field is always encoded in (val-2) format, this translates to 0x400
dwords for the true maximum length of the instruction.  Subtracting the
instruction header (1 dword) and address (2 dwords), that leaves 0x3FD
dwords (i.e., 0x1FE qwords) for PTE values.

Bspec: 60246, 45753
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20240111220238.1467572-2-matthew.d.roper@intel.comSigned-off-by: Matt Roper <matthew.d.roper@intel.com>

drivers/gpu/drm/xe/xe_migrate.c

@@ -72,6 +72,15 @@ struct xe_migrate {
 #define NUM_PT_SLOTS 32
 #define LEVEL0_PAGE_TABLE_ENCODE_SIZE SZ_2M
 
+/*
+ * Although MI_STORE_DATA_IMM's "length" field is 10-bits, 0x3FE is the largest
+ * legal value accepted.  Since that instruction field is always stored in
+ * (val-2) format, this translates to 0x400 dwords for the true maximum length
+ * of the instruction.  Subtracting the instruction header (1 dword) and
+ * address (2 dwords), that leaves 0x3FD dwords (0x1FE qwords) for PTE values.
+ */
+#define MAX_PTE_PER_SDI 0x1FE
+
 /**
  * xe_tile_migrate_engine() - Get this tile's migrate engine.
  * @tile: The tile.
@@ -444,7 +453,7 @@ static u32 pte_update_size(struct xe_migrate *m,
 		*L0_ofs = xe_migrate_vm_addr(pt_ofs, 0);
 
 		/* MI_STORE_DATA_IMM */
-		cmds += 3 * DIV_ROUND_UP(num_4k_pages, 0x1ff);
+		cmds += 3 * DIV_ROUND_UP(num_4k_pages, MAX_PTE_PER_SDI);
 
 		/* PDE qwords */
 		cmds += num_4k_pages * 2;
@@ -479,7 +488,7 @@ static void emit_pte(struct xe_migrate *m,
 	ptes = DIV_ROUND_UP(size, XE_PAGE_SIZE);
 
 	while (ptes) {
-		u32 chunk = min(0x1ffU, ptes);
+		u32 chunk = min(MAX_PTE_PER_SDI, ptes);
 
 		bb->cs[bb->len++] = MI_STORE_DATA_IMM | MI_SDI_NUM_QW(chunk);
 		bb->cs[bb->len++] = ofs;
@@ -1098,7 +1107,7 @@ static void write_pgtable(struct xe_tile *tile, struct xe_bb *bb, u64 ppgtt_ofs,
 	 * This shouldn't be possible in practice.. might change when 16K
 	 * pages are used. Hence the assert.
 	 */
-	xe_tile_assert(tile, update->qwords <= 0x1ff);
+	xe_tile_assert(tile, update->qwords <= MAX_PTE_PER_SDI);
 	if (!ppgtt_ofs)
 		ppgtt_ofs = xe_migrate_vram_ofs(tile_to_xe(tile),
 						xe_bo_addr(update->pt_bo, 0,
@@ -1107,7 +1116,7 @@ static void write_pgtable(struct xe_tile *tile, struct xe_bb *bb, u64 ppgtt_ofs,
 	do {
 		u64 addr = ppgtt_ofs + ofs * 8;
 
-		chunk = min(update->qwords, 0x1ffU);
+		chunk = min(update->qwords, MAX_PTE_PER_SDI);
 
 		/* Ensure populatefn can do memset64 by aligning bb->cs */
 		if (!(bb->len & 1))
@@ -1283,7 +1292,7 @@ xe_migrate_update_pgtables(struct xe_migrate *m,
 		batch_size = 6 + num_updates * 2;
 
 	for (i = 0; i < num_updates; i++) {
-		u32 num_cmds = DIV_ROUND_UP(updates[i].qwords, 0x1ff);
+		u32 num_cmds = DIV_ROUND_UP(updates[i].qwords, MAX_PTE_PER_SDI);
 
 		/* align noop + MI_STORE_DATA_IMM cmd prefix */
 		batch_size += 4 * num_cmds + updates[i].qwords * 2;