[PATCH] drm/i915/guc/slpc: Use non-blocking H2G for waitboost

From: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
To: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org
Cc: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Subject: [PATCH] drm/i915/guc/slpc: Use non-blocking H2G for waitboost
Date: Sat, 14 May 2022 23:05:06 -0700	[thread overview]
Message-ID: <20220515060506.22084-1-vinay.belgaumkar@intel.com> (raw)

SLPC min/max frequency updates require H2G calls. We are seeing
timeouts when GuC channel is backed up and it is unable to respond
in a timely fashion causing warnings and affecting CI.

This is seen when waitboosting happens during a stress test.
this patch updates the waitboost path to use a non-blocking
H2G call instead, which returns as soon as the message is
successfully transmitted.

v2: Use drm_notice to report any errors that might occur while
sending the waitboost H2G request (Tvrtko)

Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
---
 drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c | 44 +++++++++++++++++----
 1 file changed, 36 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c
index 1db833da42df..e5e869c96262 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c
@@ -98,6 +98,30 @@ static u32 slpc_get_state(struct intel_guc_slpc *slpc)
 	return data->header.global_state;
 }
 
+static int guc_action_slpc_set_param_nb(struct intel_guc *guc, u8 id, u32 value)
+{
+	u32 request[] = {
+		GUC_ACTION_HOST2GUC_PC_SLPC_REQUEST,
+		SLPC_EVENT(SLPC_EVENT_PARAMETER_SET, 2),
+		id,
+		value,
+	};
+	int ret;
+
+	ret = intel_guc_send_nb(guc, request, ARRAY_SIZE(request), 0);
+
+	return ret > 0 ? -EPROTO : ret;
+}
+
+static int slpc_set_param_nb(struct intel_guc_slpc *slpc, u8 id, u32 value)
+{
+	struct intel_guc *guc = slpc_to_guc(slpc);
+
+	GEM_BUG_ON(id >= SLPC_MAX_PARAM);
+
+	return guc_action_slpc_set_param_nb(guc, id, value);
+}
+
 static int guc_action_slpc_set_param(struct intel_guc *guc, u8 id, u32 value)
 {
 	u32 request[] = {
@@ -208,12 +232,10 @@ static int slpc_force_min_freq(struct intel_guc_slpc *slpc, u32 freq)
 	 */
 
 	with_intel_runtime_pm(&i915->runtime_pm, wakeref) {
-		ret = slpc_set_param(slpc,
-				     SLPC_PARAM_GLOBAL_MIN_GT_UNSLICE_FREQ_MHZ,
-				     freq);
-		if (ret)
-			i915_probe_error(i915, "Unable to force min freq to %u: %d",
-					 freq, ret);
+		/* Non-blocking request will avoid stalls */
+		ret = slpc_set_param_nb(slpc,
+					SLPC_PARAM_GLOBAL_MIN_GT_UNSLICE_FREQ_MHZ,
+					freq);
 	}
 
 	return ret;
@@ -222,6 +244,8 @@ static int slpc_force_min_freq(struct intel_guc_slpc *slpc, u32 freq)
 static void slpc_boost_work(struct work_struct *work)
 {
 	struct intel_guc_slpc *slpc = container_of(work, typeof(*slpc), boost_work);
+	struct drm_i915_private *i915 = slpc_to_i915(slpc);
+	int err;
 
 	/*
 	 * Raise min freq to boost. It's possible that
@@ -231,8 +255,12 @@ static void slpc_boost_work(struct work_struct *work)
 	 */
 	mutex_lock(&slpc->lock);
 	if (atomic_read(&slpc->num_waiters)) {
-		slpc_force_min_freq(slpc, slpc->boost_freq);
-		slpc->num_boosts++;
+		err = slpc_force_min_freq(slpc, slpc->boost_freq);
+		if (!err)
+			slpc->num_boosts++;
+		else
+			drm_notice(&i915->drm, "Failed to send waitboost request (%d)\n",
+				   err);
 	}
 	mutex_unlock(&slpc->lock);
 }
-- 
2.35.1

