drm/i915: Only access SFC_DONE when media domain is not fused off

The SFC_DONE register lives within the corresponding VD0/VD2/VD4/VD6
forcewake domain and is not accessible if the vdbox in that domain is
fused off and the forcewake is not initialized.

This mistake went unnoticed because until recently we were using the
wrong register offset for the SFC_DONE register; once the register
offset was corrected, we started hitting errors like

  <4> [544.989065] i915 0000:cc:00.0: Uninitialized forcewake domain(s) 0x80 accessed at 0x1ce000

on parts with fused-off vdbox engines.

Fixes: e50dbdbf ("drm/i915/tgl: Add SFC instdone to error state")
Fixes: 82929a21 ("drm/i915: Correct SFC_DONE register offset")
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210806174130.1058960-1-matthew.d.roper@intel.comReviewed-by: José Roberto de Souza <jose.souza@intel.com>

drivers/gpu/drm/i915/i915_gpu_error.c

@@ -727,9 +727,18 @@ static void err_print_gt(struct drm_i915_error_state_buf *m,
 	if (GRAPHICS_VER(m->i915) >= 12) {
 		int i;
 
-		for (i = 0; i < GEN12_SFC_DONE_MAX; i++)
+		for (i = 0; i < GEN12_SFC_DONE_MAX; i++) {
+			/*
+			 * SFC_DONE resides in the VD forcewake domain, so it
+			 * only exists if the corresponding VCS engine is
+			 * present.
+			 */
+			if (!HAS_ENGINE(gt->_gt, _VCS(i * 2)))
+				continue;
+
 			err_printf(m, "  SFC_DONE[%d]: 0x%08x\n", i,
 				   gt->sfc_done[i]);
+		}
 
 		err_printf(m, "  GAM_DONE: 0x%08x\n", gt->gam_done);
 	}
@@ -1581,6 +1590,14 @@ static void gt_record_regs(struct intel_gt_coredump *gt)
 
 	if (GRAPHICS_VER(i915) >= 12) {
 		for (i = 0; i < GEN12_SFC_DONE_MAX; i++) {
+			/*
+			 * SFC_DONE resides in the VD forcewake domain, so it
+			 * only exists if the corresponding VCS engine is
+			 * present.
+			 */
+			if (!HAS_ENGINE(gt->_gt, _VCS(i * 2)))
+				continue;
+
 			gt->sfc_done[i] =
 				intel_uncore_read(uncore, GEN12_SFC_DONE(i));
 		}