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

[Vinay Belgaumkar <vinay.belgaumkar@xxxxxxxxx>]

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.

Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@xxxxxxxxx>
---
 drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c | 38 ++++++++++++++++-----
 1 file changed, 30 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..c852f73cf521 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;
@@ -231,8 +253,8 @@ 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++;
+		if (!slpc_force_min_freq(slpc, slpc->boost_freq))
+			slpc->num_boosts++;
 	}
 	mutex_unlock(&slpc->lock);
 }
-- 
2.35.1