Re: [PATCH 2/4] drm/i915/tgl: Define MOCS entries for Tigerlake

Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx> · Fri, 26 Jul 2019 13:17:06 -0700

On 7/26/19 12:31 PM, Lucas De Marchi wrote:
On Fri, Jul 26, 2019 at 11:38:16AM -0700, Daniele Ceraolo Spurio wrote:


On 7/25/19 5:12 PM, Lucas De Marchi wrote:
From: Tomasz Lis <tomasz.lis@xxxxxxxxx>

The MOCS table is published as part of bspec, and versioned. Entries
are supposed to never be modified, but new ones can be added. Adding
entries increases table version. The patch includes version 1 entries.

Two of the 3 legacy entries used for gen9 are no longer expected to 
work.
Although we are changing the gen11 table, those changes are supposed to
be backward compatible since we are only touching previously undefined
entries.

v2: Add the missing entries in 49-51 range and replace "HW reserved"
    terminology to what it actually is: L1 is implicitly enabled 
(from Daniele)

Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>
Signed-off-by: Tomasz Lis <tomasz.lis@xxxxxxxxx>
Signed-off-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
---
 drivers/gpu/drm/i915/gt/intel_mocs.c | 37 +++++++++++++++++++++++++---
 1 file changed, 34 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_mocs.c 
b/drivers/gpu/drm/i915/gt/intel_mocs.c
index 290a5e9b90b9..ca370c7487f9 100644
--- a/drivers/gpu/drm/i915/gt/intel_mocs.c
+++ b/drivers/gpu/drm/i915/gt/intel_mocs.c
@@ -62,6 +62,10 @@ struct drm_i915_mocs_table {
 #define GEN11_NUM_MOCS_ENTRIES    64  /* 63-64 are reserved, but 
configured. */
 /* (e)LLC caching options */
+/*
+ * Note: LE_0_PAGETABLE works only up to Gen11; for newer gens it means
+ * the same as LE_UC
+ */
 #define LE_0_PAGETABLE        _LE_CACHEABILITY(0)
 #define LE_1_UC            _LE_CACHEABILITY(1)
 #define LE_2_WT            _LE_CACHEABILITY(2)
@@ -100,8 +104,9 @@ struct drm_i915_mocs_table {
  * of bspec.
  *
  * Entries not part of the following tables are undefined as far as
- * userspace is concerned and shouldn't be relied upon.  For the time
- * being they will be initialized to PTE.
+ * userspace is concerned and shouldn't be relied upon.  For Gen < 12
+ * they will be initialized to PTE. Gen >= 12 onwards don't have a 
setting for
+ * PTE. We use the same value, but that actually means Uncached.
  *
  * The last two entries are reserved by the hardware. For ICL+ they
  * should be initialized according to bspec and never used, for older
@@ -137,11 +142,13 @@ static const struct drm_i915_mocs_entry 
broxton_mocs_table[] = {
 };
 #define GEN11_MOCS_ENTRIES \
-    /* Base - Uncached (Deprecated) */ \
+    /* Gen11: Base - Uncached (Deprecated) */ \
+    /* Gen12+: Base - Error (Reserved for Non-Use) */ \
     MOCS_ENTRY(I915_MOCS_UNCACHED, \
            LE_1_UC | LE_TC_1_LLC, \
            L3_1_UC), \
     /* Base - L3 + LeCC:PAT (Deprecated) */ \
+    /* Gen12+: Base - Reserved */ \
     MOCS_ENTRY(I915_MOCS_PTE, \
            LE_0_PAGETABLE | LE_TC_1_LLC, \
            L3_3_WB), \


I've double-checked the specs and noticed that they now say that MOCS 
0 and 1 should be set to all zeros for Gen12 (possibly just to 
highlight the fact that they're deprecated/reserved). These are not 
supposes to be used so programming them to different values shouldn't 
matter, but it might be worth sticking to the specs and add a separate 
Gen12 table.

I noticed that too, but while implementing the IGT tests. These are 0,
but they are RO, it doesn't matter what we write on them.

I could add a comment here and change the IGT test to check they are in
fact 0 (rather than setting them as unused). Would this cover your
concern? I feel reluctant to add a big table like this per platform if
there's a wayto avoid it.


Yes, that works for me.

Daniele



I've confirmed all the other entries in the gen11 table are kept the 
same in the TGL one, and the ones added below match the table as well.

@@ -233,6 +240,30 @@ static const struct drm_i915_mocs_entry 
broxton_mocs_table[] = {
     MOCS_ENTRY(23, \
            LE_3_WB | LE_TC_1_LLC | LE_LRUM(3) | LE_RSC(1) | 
LE_SCC(7), \
            L3_3_WB), \
+    /* Gen12+: Implicitly enable L1 - HDC:L1 + L3 + LLC */ \
+    MOCS_ENTRY(48, \
+           LE_3_WB | LE_TC_1_LLC | LE_LRUM(3), \
+           L3_3_WB), \
+    /* Gen12+: Implicitly enable L1 - HDC:L1 + L3 */ \
+    MOCS_ENTRY(49, \
+           LE_1_UC | LE_TC_1_LLC, \
+           L3_3_WB), \
+    /* Gen12+: Implicitly enable L1 - HDC:L1 + LLC */ \
+    MOCS_ENTRY(50, \
+           LE_3_WB | LE_TC_1_LLC | LE_LRUM(3), \
+           L3_1_UC), \
+    /* Gen12+: Implicitly enable L1 - HDC:L1 */ \
+    MOCS_ENTRY(51, \
+           LE_1_UC | LE_TC_1_LLC, \
+           L3_1_UC), \
+    /* Gen12+: HW Reserved - HW Special Case (CCS) */ \

Entries 60 and 61 are not reserved for HW usage but are special cases 
that trigger implicit behaviors. I'd drop the "HW Reserved" tag and 
leave just "HW Special Case"

ok

thanks
Lucas De Marchi


Daniele

+    MOCS_ENTRY(60, \
+           LE_3_WB | LE_TC_1_LLC | LE_LRUM(3), \
+           L3_1_UC), \
+    /* Gen12+: HW Reserved - HW Special Case (Displayable) */ \
+    MOCS_ENTRY(61, \
+           LE_1_UC | LE_TC_1_LLC | LE_SCF(1), \
+           L3_3_WB), \
     /* HW Reserved - SW program but never use */ \
     MOCS_ENTRY(62, \
            LE_3_WB | LE_TC_1_LLC | LE_LRUM(3), \

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