Re: [PATCH v2 1/1] drm/i915/gt: Initialize reserved and unspecified MOCS indices

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On Thu, Jul 02, 2020 at 07:19:03PM +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.

V2: As suggested by Lucas "De Marchi" to utilise __init_mocs_table for
programming default value, setting I915_MOCS_PTE index of tgl_mocs_table
with desired value.

either Lucas or Lucas De Marchi, but quoting last name like this is too
creative.

Also, check for some typos below. Other than those,

Reviewed-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>



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 | 15 +++++++++++----
1 file changed, 11 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..c32f90bd56693 100644
--- a/drivers/gpu/drm/i915/gt/intel_mocs.c
+++ b/drivers/gpu/drm/i915/gt/intel_mocs.c
@@ -234,11 +234,17 @@ 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),

+	/* 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. We are programming index I915_MOCS_PTE(1)
+	 * only, __init_mocs_table() take care to prgramm unseud index with

	/* NOTE:
	 * Reserved and unspecified MOCS indices have been set to (L3 + LCC).
	 * These reserved entries should never be used, they may be changed
	 * to low performant variants with better coherency in the future if
	 * more entries are needed. We are programming index I915_MOCS_PTE(1)
	 * only, __init_mocs_table() takes care to program unused index with


Lucas De Marchi

+	 * this entry.
+	 */
+	MOCS_ENTRY(1, LE_3_WB | LE_TC_1_LLC | LE_LRUM(3),
+		   L3_3_WB),
	GEN11_MOCS_ENTRIES,

	/* Implicitly enable L1 - HDC:L1 + L3 + LLC */
@@ -265,6 +271,7 @@ static const struct drm_i915_mocs_entry tgl_mocs_table[] = {
	MOCS_ENTRY(61,
		   LE_1_UC | LE_TC_1_LLC,
		   L3_3_WB),
+
};

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

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