Historically we've initialized all undefined/reserved entries in
a platform's MOCS table to the contents of table entry #1 (i.e.,
I915_MOCS_PTE).
Going forward, we can't assume that table entry #1 will always
contain suitable values to use for undefined/reserved table
indices. We'll allow a platform-specific table index to be
selected at table initialization time in these cases.
This new mechanism to select L3 WB entry will be applicable for
all the Gen12+ platforms except TGL and RKL.
Since TGL and RLK are already in production so their mocs settings
are intact to avoid ABI break.
Signed-off-by: Ayaz A Siddiqui <ayaz.siddiqui@xxxxxxxxx>
---
drivers/gpu/drm/i915/gt/intel_mocs.c | 41 +++++++++++++++-------------
1 file changed, 22 insertions(+), 19 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_mocs.c b/drivers/gpu/drm/i915/gt/intel_mocs.c
index 82eafa8d22453..a97cc08e5a395 100644
--- a/drivers/gpu/drm/i915/gt/intel_mocs.c
+++ b/drivers/gpu/drm/i915/gt/intel_mocs.c
@@ -25,6 +25,7 @@ struct drm_i915_mocs_table {
unsigned int n_entries;
const struct drm_i915_mocs_entry *table;
u8 uc_index;
+ u8 unused_entries_index;
};
enum register_type {
@@ -113,18 +114,25 @@ struct drm_i915_aux_table {
*
* Entries not part of the following tables are undefined as far as
* 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 and will be initialized to an invalid value.
+ * they will be initialized to PTE. Gen >= 12 don't have a setting for
+ * PTE and those platforms except TGL/RKL will be initialized L3 WB to
+ * catch accidental use of reserved and unused mocs indexes.
*
* The last few entries are reserved by the hardware. For ICL+ they
* should be initialized according to bspec and never used, for older
* platforms they should never be written to.
*
- * NOTE: These tables are part of bspec and defined as part of hardware
+ * NOTE1: These tables are part of bspec and defined as part of hardware
* interface for ICL+. For older platforms, they are part of kernel
* ABI. It is expected that, for specific hardware platform, existing
* entries will remain constant and the table will only be updated by
* adding new entries, filling unused positions.
+ *
+ * NOTE2: For GEN >= 12 except TGL and RKL, reserved and unspecified MOCS
+ * indices have been set to L3 WB. 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.
+ * For TGL/RKL, all the unspecified MOCS indexes are mapped to L3 UC.
*/
#define GEN9_MOCS_ENTRIES \
MOCS_ENTRY(I915_MOCS_UNCACHED, \
@@ -307,17 +315,9 @@ static const struct drm_i915_mocs_entry icl_mocs_table[] = {
};
static const struct drm_i915_mocs_entry dg1_mocs_table[] = {
- /* Error */
- MOCS_ENTRY(0, 0, L3_0_DIRECT),
/* UC */
MOCS_ENTRY(1, 0, L3_1_UC),
-
- /* Reserved */
- MOCS_ENTRY(2, 0, L3_0_DIRECT),
- MOCS_ENTRY(3, 0, L3_0_DIRECT),
- MOCS_ENTRY(4, 0, L3_0_DIRECT),
-
/* WB - L3 */
MOCS_ENTRY(5, 0, L3_3_WB),
/* WB - L3 50% */
@@ -469,6 +469,7 @@ static unsigned int get_mocs_settings(const struct drm_i915_private *i915,
table->table = dg1_mocs_table;
table->n_entries = GEN9_NUM_MOCS_ENTRIES;
table->uc_index = 1;
+ table->unused_entries_index = 5;
} else if (GRAPHICS_VER(i915) >= 12) {
table->size = ARRAY_SIZE(tgl_mocs_table);
table->table = tgl_mocs_table;
@@ -600,16 +601,17 @@ int apply_mocs_aux_regs_ctx(struct i915_request *rq)
}
/*
- * Get control_value from MOCS entry taking into account when it's not used:
- * I915_MOCS_PTE's value is returned in this case.
+ * Get control_value from MOCS entry taking into account when it's not used
+ * then if unused_entries_index is non-zero then its value will be returned
+ * otherwise I915_MOCS_PTE's value is returned in this case.
*/
static u32 get_entry_control(const struct drm_i915_mocs_table *table,
unsigned int index)
{
if (index < table->size && table->table[index].used)
return table->table[index].control_value;
-
- return table->table[I915_MOCS_PTE].control_value;
+ index = table->unused_entries_index ? : I915_MOCS_PTE;
+ return table->table[index].control_value;
}
#define for_each_mocs(mocs, t, i) \
@@ -650,16 +652,17 @@ static void init_mocs_table(struct intel_engine_cs *engine,
}
/*
- * Get l3cc_value from MOCS entry taking into account when it's not used:
- * I915_MOCS_PTE's value is returned in this case.
+ * Get l3cc_value from MOCS entry taking into account when it's not used
+ * then if unused_entries_index is not zero then its value will be returned
+ * otherwise I915_MOCS_PTE's value is returned in this case.
*/
static u16 get_entry_l3cc(const struct drm_i915_mocs_table *table,
unsigned int index)
{
if (index < table->size && table->table[index].used)
return table->table[index].l3cc_value;
-
- return table->table[I915_MOCS_PTE].l3cc_value;
+ index = table->unused_entries_index ? : I915_MOCS_PTE;
+ return table->table[index].l3cc_value;
}
static u32 l3cc_combine(u16 low, u16 high)
--
2.26.2
