Re: [PATCH 1/1] drm/i915/gt: Initialize reserved and unspecified MOCS indices

Lucas De Marchi <lucas.demarchi@xxxxxxxxx> · Mon, 22 Jun 2020 23:15:59 -0700

On Tue, Jun 23, 2020 at 10:29:57AM +0530, Ayaz A Siddiqui wrote:
In order to avoid functional breakage of mis-programmed applications that
have grown to depend on unused MOCS entries, we are programming
those entries to be equal to fully cached ("L3 + LLC") entry.

These reserved and unspecified entries should not be used as they may be
changed to less performant variants with better coherency in the future
if more entries are needed.

Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
Cc: Tomasz Lis <tomasz.lis@xxxxxxxxx>
Cc: Matt Roper <matthew.d.roper@xxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Francisco Jerez <currojerez@xxxxxxxxxx>
Cc: Mathew, Alwin <alwin.mathew@xxxxxxxxx>
Cc: Mcguire, Russell W <russell.w.mcguire@xxxxxxxxx>
Cc: Spruit, Neil R <neil.r.spruit@xxxxxxxxx>
Cc: Zhou, Cheng <cheng.zhou@xxxxxxxxx>
Cc: Benemelis, Mike G <mike.g.benemelis@xxxxxxxxx>

Signed-off-by: Ayaz A Siddiqui <ayaz.siddiqui@xxxxxxxxx>
---
drivers/gpu/drm/i915/gt/intel_mocs.c | 93 ++++++++++++++++++++++++++--
1 file changed, 89 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_mocs.c b/drivers/gpu/drm/i915/gt/intel_mocs.c
index 632e08a4592b2..1089bd5fdba2c 100644
--- a/drivers/gpu/drm/i915/gt/intel_mocs.c
+++ b/drivers/gpu/drm/i915/gt/intel_mocs.c
@@ -234,10 +234,6 @@ static const struct drm_i915_mocs_entry broxton_mocs_table[] = {
		   L3_1_UC)

static const struct drm_i915_mocs_entry tgl_mocs_table[] = {
-	/* Base - Error (Reserved for Non-Use) */
-	MOCS_ENTRY(0, 0x0, 0x0),
-	/* Base - Reserved */
-	MOCS_ENTRY(1, 0x0, 0x0),

	GEN11_MOCS_ENTRIES,

@@ -265,6 +261,95 @@ static const struct drm_i915_mocs_entry tgl_mocs_table[] = {
	MOCS_ENTRY(61,
		   LE_1_UC | LE_TC_1_LLC,
		   L3_3_WB),
+
+	/* NOTE:
+	 * Reserved and unspecified MOCS indices have been set to (L3 + LCC).
+	 * These reserved entry should never be used, they may be chanaged
+	 * to low performant variants with better coherency in the future if
+	 * more entries are needed.
+	 */

the whole point of structing this table the way it is is that it doesn't
take more space than needed and we can override values from previous
platforms.

MOCS_ENTRY() will set .used = 1. It seems that what you want is to
actually change the value when .used == 0 is set.

It seems you actually want to set the unused ones to that specific
value. See __init_mocs_table()

Lucas De Marchi

+
+	/* Reserved index 0 and 1 */
+	MOCS_ENTRY(0, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(1, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+
+	/* Reserved index 16 and 17 */
+	MOCS_ENTRY(16, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(17, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+
+	/* Reserved index 24 and 25 */
+	MOCS_ENTRY(24, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(25, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+
+	/* Unspecified indices 26 to 47 */
+	MOCS_ENTRY(26, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(27, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(28, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(29, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(30, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(31, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(32, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(33, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(34, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(35, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(36, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(37, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(38, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(39, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(40, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(41, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(42, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(43, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(44, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(45, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(46, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(47, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+
+	/* Unspecified indices 52 to 59 */
+	MOCS_ENTRY(52, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(53, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(54, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(55, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(56, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(57, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(58, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
+	MOCS_ENTRY(59, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB)
};

static const struct drm_i915_mocs_entry icl_mocs_table[] = {
--
2.26.2

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