[Intel-gfx] [PATCH v2 1/1] drm/i915/guc: Fix GuC error capture sizing estimation and reporting

[Alan Previn]

During GuC error capture initialization, we estimate the amount of size
we need for the error-capture-region of the shared GuC-log-buffer.
This calculation was incorrect so fix that. Additionally, if the size
was insufficient, don't drm_warn or drm_notice, just drm_debug since
actually running out based on that estimation is a corner case. It
can only occur if all engine instances get reset all at once and i915
isn't able extract the capture data fast enough within G2H handler
worker.

Fixes d7c15d76a5547: drm/i915/guc: Check sizing of guc_capture output

Signed-off-by: Alan Previn <alan.previn.teres.alexis at intel.com>
---
 .../gpu/drm/i915/gt/uc/intel_guc_capture.c    | 29 ++++++++++++-------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_capture.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_capture.c
index 8f1165146013..b3c6ed839163 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_capture.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_capture.c
@@ -502,8 +502,9 @@ intel_guc_capture_getlistsize(struct intel_guc *guc, u32 owner, u32 type, u32 cl
 	if (!num_regs)
 		return -ENODATA;
 
-	*size = PAGE_ALIGN((sizeof(struct guc_debug_capture_list)) +
-			   (num_regs * sizeof(struct guc_mmio_reg)));
+	if (size)
+		*size = PAGE_ALIGN((sizeof(struct guc_debug_capture_list)) +
+				   (num_regs * sizeof(struct guc_mmio_reg)));
 
 	return 0;
 }
@@ -606,7 +607,7 @@ guc_capture_output_min_size_est(struct intel_guc *guc)
 	struct intel_gt *gt = guc_to_gt(guc);
 	struct intel_engine_cs *engine;
 	enum intel_engine_id id;
-	int worst_min_size = 0, num_regs = 0;
+	int worst_min_size = 0;
 	size_t tmp = 0;
 
 	if (!guc->capture)
@@ -628,20 +629,18 @@ guc_capture_output_min_size_est(struct intel_guc *guc)
 					 (3 * sizeof(struct guc_state_capture_header_t));
 
 		if (!intel_guc_capture_getlistsize(guc, 0, GUC_CAPTURE_LIST_TYPE_GLOBAL, 0, &tmp))
-			num_regs += tmp;
+			worst_min_size += tmp;
 
 		if (!intel_guc_capture_getlistsize(guc, 0, GUC_CAPTURE_LIST_TYPE_ENGINE_CLASS,
 						   engine->class, &tmp)) {
-			num_regs += tmp;
+			worst_min_size += tmp;
 		}
 		if (!intel_guc_capture_getlistsize(guc, 0, GUC_CAPTURE_LIST_TYPE_ENGINE_INSTANCE,
 						   engine->class, &tmp)) {
-			num_regs += tmp;
+			worst_min_size += tmp;
 		}
 	}
 
-	worst_min_size += (num_regs * sizeof(struct guc_mmio_reg));
-
 	return worst_min_size;
 }
 
@@ -658,15 +657,23 @@ static void check_guc_capture_size(struct intel_guc *guc)
 	int spare_size = min_size * GUC_CAPTURE_OVERBUFFER_MULTIPLIER;
 	u32 buffer_size = intel_guc_log_section_size_capture(&guc->log);
 
+	/*
+	 * Don't drm_warn or drm_error here on "possible" insufficient size because we only run out
+	 * of space if all engines were to suffer resets all at once AND the driver is not able to
+	 * extract that data fast enough in the interrupt handler worker (moving them to the
+	 * larger pool of pre-allocated capture nodes. If GuC does run out of space, we will
+	 * print an error when processing the G2H event capture-notification (search for
+	 * "INTEL_GUC_STATE_CAPTURE_EVENT_STATUS_NOSPACE").
+	 */
 	if (min_size < 0)
 		drm_warn(&i915->drm, "Failed to calculate GuC error state capture buffer minimum size: %d!\n",
 			 min_size);
 	else if (min_size > buffer_size)
-		drm_warn(&i915->drm, "GuC error state capture buffer is too small: %d < %d\n",
+		drm_warn(&i915->drm, "GuC error state capture buffer maybe small: %d < %d\n",
 			 buffer_size, min_size);
 	else if (spare_size > buffer_size)
-		drm_notice(&i915->drm, "GuC error state capture buffer maybe too small: %d < %d (min = %d)\n",
-			   buffer_size, spare_size, min_size);
+		drm_dbg(&i915->drm, "GuC error state capture buffer lacks spare size: %d < %d (min = %d)\n",
+			buffer_size, spare_size, min_size);
 }
 
 /*
-- 
2.34.1