[v2,1/1] drm/i915/gt: Initialize reserved and unspecified MOCS indices
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Message ID 20200702134903.602364-2-ayaz.siddiqui@intel.com
State New
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  • drm/i915/gt: Initialize reserved and unspecified MOCS indices
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Commit Message

Siddiqui, Ayaz A July 2, 2020, 1:49 p.m. UTC
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.

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

Signed-off-by: Ayaz A Siddiqui <ayaz.siddiqui@intel.com>
---
 drivers/gpu/drm/i915/gt/intel_mocs.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

Comments

Lucas De Marchi July 6, 2020, 4:36 p.m. UTC | #1
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@intel.com>


>
>Cc: Chris Wilson <chris@chris-wilson.co.uk>
>Cc: Lucas De Marchi <lucas.demarchi@intel.com>
>Cc: Tomasz Lis <tomasz.lis@intel.com>
>Cc: Matt Roper <matthew.d.roper@intel.com>
>Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
>Cc: Francisco Jerez <currojerez@riseup.net>
>Cc: Mathew Alwin <alwin.mathew@intel.com>
>Cc: Mcguire Russell W <russell.w.mcguire@intel.com>
>Cc: Spruit Neil R <neil.r.spruit@intel.com>
>Cc: Zhou Cheng <cheng.zhou@intel.com>
>Cc: Benemelis Mike G <mike.g.benemelis@intel.com>
>
>Signed-off-by: Ayaz A Siddiqui <ayaz.siddiqui@intel.com>
>---
> 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
>

Patch
diff mbox series

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
+	 * 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[] = {