drm/i915/icl: new context descriptor support

Starting from Gen11 the context descriptor format has been updated in
the HW. The hw_id field has been considerably reduced in size and engine
class and instance fields have been added.

There is a slight name clashing issue because the field that we call
hw_id is actually called SW Context ID in the specs for Gen11+.

With the current size of the hw_id field we can have a maximum of 2k
contexts at any time, but we could use the sw_counter field (which is sw
defined) to increase that because the HW requirement is that
engine_id + sw id + sw_counter is a unique number.
GuC uses a similar method to support more contexts but does its tracking
at lrc level. To avoid doing an implementation that will need to be
reworked once GuC support lands, defer it for now and mark it as TODO.

v2: rebased, add documentation, fix GEN11_ENGINE_INSTANCE_SHIFT
v3: rebased, bring back lost code from i915_gem_context.c
v4: make TODO comment more generic
v5: be consistent with bit ordering, add extra checks (Chris)

Cc: Oscar Mateo <oscar.mateo@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Oscar Mateo <oscar.mateo@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180302161501.28594-3-mika.kuoppala@linux.intel.com
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>

1 files changed, 34 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 75d2daa..69838f6 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -204,6 +204,18 @@ static inline bool need_preempt(const struct intel_engine_cs *engine,
  *      bits 32-52:    ctx ID, a globally unique tag
  *      bits 53-54:    mbz, reserved for use by hardware
  *      bits 55-63:    group ID, currently unused and set to 0
+ *
+ * Starting from Gen11, the upper dword of the descriptor has a new format:
+ *
+ *      bits 32-36:    reserved
+ *      bits 37-47:    SW context ID
+ *      bits 48:53:    engine instance
+ *      bit 54:        mbz, reserved for use by hardware
+ *      bits 55-60:    SW counter
+ *      bits 61-63:    engine class
+ *
+ * engine info, SW context ID and SW counter need to form a unique number
+ * (Context ID) per lrc.
  */
 static void
 intel_lr_context_descriptor_update(struct i915_gem_context *ctx,
@@ -212,12 +224,32 @@ intel_lr_context_descriptor_update(struct i915_gem_context *ctx,
 	struct intel_context *ce = &ctx->engine[engine->id];
 	u64 desc;
 
-	BUILD_BUG_ON(MAX_CONTEXT_HW_ID > (1<<GEN8_CTX_ID_WIDTH));
+	BUILD_BUG_ON(MAX_CONTEXT_HW_ID > (BIT(GEN8_CTX_ID_WIDTH)));
+	BUILD_BUG_ON(GEN11_MAX_CONTEXT_HW_ID > (BIT(GEN11_SW_CTX_ID_WIDTH)));
 
 	desc = ctx->desc_template;				/* bits  0-11 */
+	GEM_BUG_ON(desc & GENMASK_ULL(63, 12));
+
 	desc |= i915_ggtt_offset(ce->state) + LRC_HEADER_PAGES * PAGE_SIZE;
 								/* bits 12-31 */
-	desc |= (u64)ctx->hw_id << GEN8_CTX_ID_SHIFT;		/* bits 32-52 */
+	GEM_BUG_ON(desc & GENMASK_ULL(63, 32));
+
+	if (INTEL_GEN(ctx->i915) >= 11) {
+		GEM_BUG_ON(ctx->hw_id >= BIT(GEN11_SW_CTX_ID_WIDTH));
+		desc |= (u64)ctx->hw_id << GEN11_SW_CTX_ID_SHIFT;
+								/* bits 37-47 */
+
+		desc |= (u64)engine->instance << GEN11_ENGINE_INSTANCE_SHIFT;
+								/* bits 48-53 */
+
+		/* TODO: decide what to do with SW counter (bits 55-60) */
+
+		desc |= (u64)engine->class << GEN11_ENGINE_CLASS_SHIFT;
+								/* bits 61-63 */
+	} else {
+		GEM_BUG_ON(ctx->hw_id >= BIT(GEN8_CTX_ID_WIDTH));
+		desc |= (u64)ctx->hw_id << GEN8_CTX_ID_SHIFT;	/* bits 32-52 */
+	}
 
 	ce->lrc_desc = desc;
 }