drm/xe/mocs: Clarify difference between hw and sw sizes

It's not very obvious what the difference is between the 'size' and
'n_entries' fields of the MOCS structure.  Rename both fields slightly
and add some comments explaining that one is the documentation-defined
table size, while the other is the number of entries that can be
programmed into the hardware (and the documented table size can
potentially be smaller than the number of hardware entries).
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240627203741.2042752-4-matthew.d.roper@intel.com

drivers/gpu/drm/xe/tests/xe_mocs.c

@@ -31,9 +31,9 @@ static int live_mocs_init(struct live_mocs *arg, struct xe_gt *gt)
 
 	kunit_info(test, "gt %d", gt->info.id);
 	kunit_info(test, "gt type %d", gt->info.type);
-	kunit_info(test, "table size %d", arg->table.size);
+	kunit_info(test, "table size %d", arg->table.table_size);
 	kunit_info(test, "table uc_index %d", arg->table.uc_index);
-	kunit_info(test, "table n_entries %d", arg->table.n_entries);
+	kunit_info(test, "table num_mocs_regs %d", arg->table.num_mocs_regs);
 
 	return flags;
 }
@@ -50,7 +50,7 @@ static void read_l3cc_table(struct xe_gt *gt,
 	ret = xe_force_wake_get(gt_to_fw(gt), XE_FW_GT);
 	KUNIT_ASSERT_EQ_MSG(test, ret, 0, "Forcewake Failed.\n");
 
-	for (i = 0; i < info->n_entries; i++) {
+	for (i = 0; i < info->num_mocs_regs; i++) {
 		if (!(i & 1)) {
 			if (regs_are_mcr(gt))
 				reg_val = xe_gt_mcr_unicast_read_any(gt, XEHP_LNCFCMOCS(i >> 1));
@@ -90,7 +90,7 @@ static void read_mocs_table(struct xe_gt *gt,
 	ret = xe_force_wake_get(gt_to_fw(gt), XE_FW_GT);
 	KUNIT_ASSERT_EQ_MSG(test, ret, 0, "Forcewake Failed.\n");
 
-	for (i = 0; i < info->n_entries; i++) {
+	for (i = 0; i < info->num_mocs_regs; i++) {
 		if (regs_are_mcr(gt))
 			reg_val = xe_gt_mcr_unicast_read_any(gt, XEHP_GLOBAL_MOCS(i));
 		else

drivers/gpu/drm/xe/xe_mocs.c

@@ -47,8 +47,16 @@ struct xe_mocs_ops {
 };
 
 struct xe_mocs_info {
-	unsigned int size;
-	unsigned int n_entries;
+	/*
+	 * Size of the spec's suggested MOCS programming table.  The list of
+	 * table entries from the spec can potentially be smaller than the
+	 * number of hardware registers used to program the MOCS table; in such
+	 * cases the registers for the remaining indices will be programmed to
+	 * match unused_entries_index.
+	 */
+	unsigned int table_size;
+	/* Number of MOCS entries supported by the hardware */
+	unsigned int num_mocs_regs;
 	const struct xe_mocs_entry *table;
 	const struct xe_mocs_ops *ops;
 	u8 uc_index;
@@ -266,7 +274,7 @@ static void xelp_lncf_dump(struct xe_mocs_info *info, struct xe_gt *gt, struct d
 
 	drm_printf(p, "LNCFCMOCS[idx] = [ESC, SCC, L3CC] (value)\n\n");
 
-	for (i = 0, j = 0; i < (info->n_entries + 1) / 2; i++, j++) {
+	for (i = 0, j = 0; i < (info->num_mocs_regs + 1) / 2; i++, j++) {
 		if (regs_are_mcr(gt))
 			reg_val = xe_gt_mcr_unicast_read_any(gt, XEHP_LNCFCMOCS(i));
 		else
@@ -298,7 +306,7 @@ static void xelp_mocs_dump(struct xe_mocs_info *info, unsigned int flags,
 		drm_printf(p, "Global mocs table configuration:\n");
 		drm_printf(p, "GLOB_MOCS[idx] = [LeCC, TC, LRUM, AOM, RSC, SCC, PFM, SCF, CoS, SSE] (value)\n\n");
 
-		for (i = 0; i < info->n_entries; i++) {
+		for (i = 0; i < info->num_mocs_regs; i++) {
 			if (regs_are_mcr(gt))
 				reg_val = xe_gt_mcr_unicast_read_any(gt, XEHP_GLOBAL_MOCS(i));
 			else
@@ -371,7 +379,7 @@ static void xehp_lncf_dump(struct xe_mocs_info *info, unsigned int flags,
 
 	drm_printf(p, "LNCFCMOCS[idx] = [UCL3LOOKUP, GLBGO, L3CC] (value)\n\n");
 
-	for (i = 0, j = 0; i < (info->n_entries + 1) / 2; i++, j++) {
+	for (i = 0, j = 0; i < (info->num_mocs_regs + 1) / 2; i++, j++) {
 		if (regs_are_mcr(gt))
 			reg_val = xe_gt_mcr_unicast_read_any(gt, XEHP_LNCFCMOCS(i));
 		else
@@ -416,7 +424,7 @@ static void pvc_mocs_dump(struct xe_mocs_info *info, unsigned int flags, struct
 
 	drm_printf(p, "LNCFCMOCS[idx] = [ L3CC ] (value)\n\n");
 
-	for (i = 0, j = 0; i < (info->n_entries + 1) / 2; i++, j++) {
+	for (i = 0, j = 0; i < (info->num_mocs_regs + 1) / 2; i++, j++) {
 		if (regs_are_mcr(gt))
 			reg_val = xe_gt_mcr_unicast_read_any(gt, XEHP_LNCFCMOCS(i));
 		else
@@ -498,7 +506,7 @@ static void mtl_mocs_dump(struct xe_mocs_info *info, unsigned int flags,
 	drm_printf(p, "Global mocs table configuration:\n");
 	drm_printf(p, "GLOB_MOCS[idx] = [IG_PAT, L4_CACHE_POLICY] (value)\n\n");
 
-	for (i = 0; i < info->n_entries; i++) {
+	for (i = 0; i < info->num_mocs_regs; i++) {
 		if (regs_are_mcr(gt))
 			reg_val = xe_gt_mcr_unicast_read_any(gt, XEHP_GLOBAL_MOCS(i));
 		else
@@ -541,7 +549,7 @@ static void xe2_mocs_dump(struct xe_mocs_info *info, unsigned int flags,
 	drm_printf(p, "Global mocs table configuration:\n");
 	drm_printf(p, "GLOB_MOCS[idx] = [IG_PAT, L3_CLOS, L3_CACHE_POLICY, L4_CACHE_POLICY] (value)\n\n");
 
-	for (i = 0; i < info->n_entries; i++) {
+	for (i = 0; i < info->num_mocs_regs; i++) {
 		if (regs_are_mcr(gt))
 			reg_val = xe_gt_mcr_unicast_read_any(gt, XEHP_GLOBAL_MOCS(i));
 		else
@@ -571,48 +579,48 @@ static unsigned int get_mocs_settings(struct xe_device *xe,
 	case XE_LUNARLAKE:
 	case XE_BATTLEMAGE:
 		info->ops = &xe2_mocs_ops;
-		info->size = ARRAY_SIZE(xe2_mocs_table);
+		info->table_size = ARRAY_SIZE(xe2_mocs_table);
 		info->table = xe2_mocs_table;
-		info->n_entries = XE2_NUM_MOCS_ENTRIES;
+		info->num_mocs_regs = XE2_NUM_MOCS_ENTRIES;
 		info->uc_index = 3;
 		info->wb_index = 4;
 		info->unused_entries_index = 4;
 		break;
 	case XE_PVC:
 		info->ops = &pvc_mocs_ops;
-		info->size = ARRAY_SIZE(pvc_mocs_desc);
+		info->table_size = ARRAY_SIZE(pvc_mocs_desc);
 		info->table = pvc_mocs_desc;
-		info->n_entries = PVC_NUM_MOCS_ENTRIES;
+		info->num_mocs_regs = PVC_NUM_MOCS_ENTRIES;
 		info->uc_index = 1;
 		info->wb_index = 2;
 		info->unused_entries_index = 2;
 		break;
 	case XE_METEORLAKE:
 		info->ops = &mtl_mocs_ops;
-		info->size = ARRAY_SIZE(mtl_mocs_desc);
+		info->table_size = ARRAY_SIZE(mtl_mocs_desc);
 		info->table = mtl_mocs_desc;
-		info->n_entries = MTL_NUM_MOCS_ENTRIES;
+		info->num_mocs_regs = MTL_NUM_MOCS_ENTRIES;
 		info->uc_index = 9;
 		info->unused_entries_index = 1;
 		break;
 	case XE_DG2:
 		info->ops = &xehp_mocs_ops;
-		info->size = ARRAY_SIZE(dg2_mocs_desc);
+		info->table_size = ARRAY_SIZE(dg2_mocs_desc);
 		info->table = dg2_mocs_desc;
 		info->uc_index = 1;
 		/*
 		 * Last entry is RO on hardware, don't bother with what was
 		 * written when checking later
 		 */
-		info->n_entries = XELP_NUM_MOCS_ENTRIES - 1;
+		info->num_mocs_regs = XELP_NUM_MOCS_ENTRIES - 1;
 		info->unused_entries_index = 3;
 		break;
 	case XE_DG1:
 		info->ops = &xelp_mocs_ops;
-		info->size = ARRAY_SIZE(dg1_mocs_desc);
+		info->table_size = ARRAY_SIZE(dg1_mocs_desc);
 		info->table = dg1_mocs_desc;
 		info->uc_index = 1;
-		info->n_entries = XELP_NUM_MOCS_ENTRIES;
+		info->num_mocs_regs = XELP_NUM_MOCS_ENTRIES;
 		info->unused_entries_index = 5;
 		break;
 	case XE_TIGERLAKE:
@@ -621,9 +629,9 @@ static unsigned int get_mocs_settings(struct xe_device *xe,
 	case XE_ALDERLAKE_P:
 	case XE_ALDERLAKE_N:
 		info->ops = &xelp_mocs_ops;
-		info->size  = ARRAY_SIZE(gen12_mocs_desc);
+		info->table_size  = ARRAY_SIZE(gen12_mocs_desc);
 		info->table = gen12_mocs_desc;
-		info->n_entries = XELP_NUM_MOCS_ENTRIES;
+		info->num_mocs_regs = XELP_NUM_MOCS_ENTRIES;
 		info->uc_index = 3;
 		info->unused_entries_index = 2;
 		break;
@@ -643,7 +651,7 @@ static unsigned int get_mocs_settings(struct xe_device *xe,
 	xe_assert(xe, info->unused_entries_index != 0);
 
 	xe_assert(xe, info->ops && info->ops->dump);
-	xe_assert(xe, info->size <= info->n_entries);
+	xe_assert(xe, info->table_size <= info->num_mocs_regs);
 
 	if (!IS_DGFX(xe) || GRAPHICS_VER(xe) >= 20)
 		flags |= HAS_GLOBAL_MOCS;
@@ -660,7 +668,7 @@ static unsigned int get_mocs_settings(struct xe_device *xe,
 static u32 get_entry_control(const struct xe_mocs_info *info,
 			     unsigned int index)
 {
-	if (index < info->size && info->table[index].used)
+	if (index < info->table_size && info->table[index].used)
 		return info->table[index].control_value;
 	return info->table[info->unused_entries_index].control_value;
 }
@@ -671,9 +679,9 @@ static void __init_mocs_table(struct xe_gt *gt,
 	unsigned int i;
 	u32 mocs;
 
-	mocs_dbg(gt, "mocs entries: %d\n", info->n_entries);
+	mocs_dbg(gt, "mocs entries: %d\n", info->num_mocs_regs);
 
-	for (i = 0; i < info->n_entries; i++) {
+	for (i = 0; i < info->num_mocs_regs; i++) {
 		mocs = get_entry_control(info, i);
 
 		mocs_dbg(gt, "GLOB_MOCS[%d] 0x%x 0x%x\n", i,
@@ -694,7 +702,7 @@ static void __init_mocs_table(struct xe_gt *gt,
 static u16 get_entry_l3cc(const struct xe_mocs_info *info,
 			  unsigned int index)
 {
-	if (index < info->size && info->table[index].used)
+	if (index < info->table_size && info->table[index].used)
 		return info->table[index].l3cc_value;
 	return info->table[info->unused_entries_index].l3cc_value;
 }
@@ -710,9 +718,9 @@ static void init_l3cc_table(struct xe_gt *gt,
 	unsigned int i;
 	u32 l3cc;
 
-	mocs_dbg(gt, "l3cc entries: %d\n", info->n_entries);
+	mocs_dbg(gt, "l3cc entries: %d\n", info->num_mocs_regs);
 
-	for (i = 0; i < (info->n_entries + 1) / 2; i++) {
+	for (i = 0; i < (info->num_mocs_regs + 1) / 2; i++) {
 		l3cc = l3cc_combine(get_entry_l3cc(info, 2 * i),
 				    get_entry_l3cc(info, 2 * i + 1));