[PATCH 2/2] drm/xe/pat: Default XE_CACHE_NONE_COMPRESSION to invalid and assert on use

[Xin Wang <x.wang@intel.com>]

Initialize XE_CACHE_NONE_COMPRESSION PAT index to XE_PAT_INVALID_IDX by
default, and add xe_assert() checks at the sites that use it for PTE
encoding. This ensures platforms that don't support this cache mode fail
loudly rather than silently encoding an invalid index into PTEs.

Suggested-by: Matthew Auld <matthew.auld@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Xin Wang <x.wang@intel.com>
---
 drivers/gpu/drm/xe/xe_migrate.c | 9 +++++++--
 drivers/gpu/drm/xe/xe_pat.c     | 1 +
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_migrate.c b/drivers/gpu/drm/xe/xe_migrate.c
index fc918b4fba54..cad47866435d 100644
--- a/drivers/gpu/drm/xe/xe_migrate.c
+++ b/drivers/gpu/drm/xe/xe_migrate.c
@@ -30,6 +30,7 @@
 #include "xe_lrc.h"
 #include "xe_map.h"
 #include "xe_mocs.h"
+#include "xe_pat.h"
 #include "xe_printk.h"
 #include "xe_pt.h"
 #include "xe_res_cursor.h"
@@ -341,6 +342,7 @@ static void xe_migrate_prepare_vm(struct xe_tile *tile, struct xe_migrate *m,
 				DIV_ROUND_UP_ULL(actual_phy_size, SZ_1G);
 			u64 pt31_ofs = xe_bo_size(bo) - XE_PAGE_SIZE;
 
+			xe_assert(xe, comp_pat_index != XE_PAT_INVALID_IDX);
 			xe_assert(xe, actual_phy_size <= (MAX_NUM_PTE - IDENTITY_OFFSET -
 							  IDENTITY_OFFSET / 2) * SZ_1G);
 			xe_migrate_program_identity(xe, vm, bo, map_ofs, vram_offset,
@@ -635,11 +637,14 @@ static void emit_pte(struct xe_migrate *m,
 	u64 cur_ofs;
 
 	/* Indirect access needs compression enabled uncached PAT index */
-	if (GRAPHICS_VERx100(xe) >= 2000)
+	if (GRAPHICS_VERx100(xe) >= 2000) {
 		pat_index = is_comp_pte ? xe->pat.idx[XE_CACHE_NONE_COMPRESSION] :
 					  xe->pat.idx[XE_CACHE_WB];
-	else
+		if (is_comp_pte)
+			xe_assert(xe, pat_index != XE_PAT_INVALID_IDX);
+	} else {
 		pat_index = xe->pat.idx[XE_CACHE_WB];
+	}
 
 	ptes = DIV_ROUND_UP(size, XE_PAGE_SIZE);
 
diff --git a/drivers/gpu/drm/xe/xe_pat.c b/drivers/gpu/drm/xe/xe_pat.c
index 75aaae7b003d..fad5b5a5ed4a 100644
--- a/drivers/gpu/drm/xe/xe_pat.c
+++ b/drivers/gpu/drm/xe/xe_pat.c
@@ -559,6 +559,7 @@ static const struct xe_pat_ops xe3p_xpc_pat_ops = {
 void xe_pat_init_early(struct xe_device *xe)
 {
 	xe->pat.idx[XE_CACHE_WB_COMPRESSION] = XE_PAT_INVALID_IDX;
+	xe->pat.idx[XE_CACHE_NONE_COMPRESSION] = XE_PAT_INVALID_IDX;
 	if (GRAPHICS_VERx100(xe) == 3511) {
 		xe->pat.ops = &xe3p_xpc_pat_ops;
 		xe->pat.table = xe3p_xpc_pat_table;
-- 
2.43.0