drm/i915/guc: Ensure G2H response has space in buffer

Ensure G2H response has space in the buffer before sending H2G CTB as
the GuC can't handle any backpressure on the G2H interface.

v2:
 (Matthew)
  - s/INTEL_GUC_SEND/INTEL_GUC_CT_SEND
v3:
 (Matthew)
  - Add G2H credit accounting to blocking path, add g2h_release_space
    helper
 (John H)
  - CTB_G2H_BUFFER_SIZE / 4 == G2H_ROOM_BUFFER_SIZE

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210721215101.139794-15-matthew.brost@intel.com

1 files changed, 10 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h
index edd1bba0445d..dda2d6a75392 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h
@@ -33,6 +33,7 @@ struct intel_guc;
  * @desc: pointer to the buffer descriptor
  * @cmds: pointer to the commands buffer
  * @size: size of the commands buffer in dwords
+ * @resv_space: reserved space in buffer in dwords
  * @head: local shadow copy of head in dwords
  * @tail: local shadow copy of tail in dwords
  * @space: local shadow copy of space in dwords
@@ -43,9 +44,10 @@ struct intel_guc_ct_buffer {
 	struct guc_ct_buffer_desc *desc;
 	u32 *cmds;
 	u32 size;
+	u32 resv_space;
 	u32 tail;
 	u32 head;
-	u32 space;
+	atomic_t space;
 	bool broken;
 };
 
@@ -97,6 +99,13 @@ static inline bool intel_guc_ct_enabled(struct intel_guc_ct *ct)
 }
 
 #define INTEL_GUC_CT_SEND_NB		BIT(31)
+#define INTEL_GUC_CT_SEND_G2H_DW_SHIFT	0
+#define INTEL_GUC_CT_SEND_G2H_DW_MASK	(0xff << INTEL_GUC_CT_SEND_G2H_DW_SHIFT)
+#define MAKE_SEND_FLAGS(len) ({ \
+	typeof(len) len_ = (len); \
+	GEM_BUG_ON(!FIELD_FIT(INTEL_GUC_CT_SEND_G2H_DW_MASK, len_)); \
+	(FIELD_PREP(INTEL_GUC_CT_SEND_G2H_DW_MASK, len_) | INTEL_GUC_CT_SEND_NB); \
+})
 int intel_guc_ct_send(struct intel_guc_ct *ct, const u32 *action, u32 len,
 		      u32 *response_buf, u32 response_buf_size, u32 flags);
 void intel_guc_ct_event_handler(struct intel_guc_ct *ct);