drm/xe/xe3p_xpc: Add support for compute walker for non-MSIx

Current implementation of compute walker has dependency on GPU/SW Stack
which requires SW/UMD to wait for event from KMD to indicate
PIPE_CONTROL interrupt was done. This created latency on SW stack.

This feature adds support to generate completion interrupt from GPGPU
walker which does not support MSIx and avoid software using Pipe control
drain/idle latency.

The only thing needed for the kernel driver to do here is to wakeup the
thread waiting on the ufence, which is already handled by the irq
handler. Before waiting on this event, the userspace side can opt-in to
this interrupt being generated by the HW by selecting the flag in the
POST_SYNC_DATA_2 substructure's dw0[3] of COMPUTE_WALKER_2 instruction.

Bspec: 62346, 74334
Suggested-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Signed-off-by: S A Muqthyar Ahmed <syed.abdul.muqthyar.ahmed@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://lore.kernel.org/r/20251016-xe3p-v3-21-3dd173a3097a@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

Author: Lucas De Marchi

drivers/gpu/drm/xe/regs/xe_irq_regs.h

@@ -85,6 +85,7 @@
 #define   GSC_ER_COMPLETE			REG_BIT(5)
 #define   GT_FLUSH_COMPLETE_INTERRUPT	REG_BIT(4)
 #define   GT_CS_MASTER_ERROR_INTERRUPT		REG_BIT(3)
+#define   GT_COMPUTE_WALKER_INTERRUPT		REG_BIT(2)
 #define   GT_MI_USER_INTERRUPT			REG_BIT(0)
 
 /* irqs for OTHER_KCR_INSTANCE */

drivers/gpu/drm/xe/xe_irq.c

@@ -149,6 +149,12 @@ void xe_irq_enable_hwe(struct xe_gt *gt)
 	if (xe_device_uc_enabled(xe)) {
 		common_mask = GT_MI_USER_INTERRUPT |
 			      GT_FLUSH_COMPLETE_INTERRUPT;
+
+		/* Enable Compute Walker Interrupt for non-MSIX platforms */
+		if (GRAPHICS_VERx100(xe) >= 3511 && !xe_device_has_msix(xe)) {
+			rcs_mask |= GT_COMPUTE_WALKER_INTERRUPT;
+			ccs_mask |= GT_COMPUTE_WALKER_INTERRUPT;
+		}
 	} else {
 		common_mask = GT_MI_USER_INTERRUPT |
 			      GT_CS_MASTER_ERROR_INTERRUPT |