drm/i915/guc/slpc: Allow SLPC to use efficient frequency

Host Turbo operates at efficient frequency when GT is not idle unless
the user or workload has forced it to a higher level. Replicate the same
behavior in SLPC by allowing the algorithm to use efficient frequency.
We had disabled it during boot due to concerns that it might break
kernel ABI for min frequency. However, this is not the case since
SLPC will still abide by the (min,max) range limits.

With this change, min freq will be at efficient frequency level at init
instead of fused min (RPn). If user chooses to reduce min freq below the
efficient freq, we will turn off usage of efficient frequency and honor
the user request. When a higher value is written, it will get toggled
back again.

The patch also corrects the register which needs to be read for obtaining
the correct efficient frequency for Gen9+.

We see much better perf numbers with benchmarks like glmark2 with
efficient frequency usage enabled as expected.

v2: Address review comments (Rodrigo)
v3: with efficient frequency being dynamic, it is possible that the req
frequency may go beyond max freq. This will cause SLPC selftests to fail.
Add a FIXME there to start the test with [RPn, RP0] instead and restore
it afterwards.

BugLink: https://gitlab.freedesktop.org/drm/intel/-/issues/5468

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220820010832.15350-1-vinay.belgaumkar@intel.com

drivers/gpu/drm/i915/gt/intel_rps.c

@@ -1107,6 +1107,11 @@ void gen6_rps_get_freq_caps(struct intel_rps *rps, struct intel_rps_freq_caps *c
 		caps->min_freq = (rp_state_cap >>  0) & 0xff;
 	} else {
 		caps->rp0_freq = (rp_state_cap >>  0) & 0xff;
+		if (GRAPHICS_VER(i915) >= 10)
+			caps->rp1_freq = REG_FIELD_GET(RPE_MASK,
+						       intel_uncore_read(to_gt(i915)->uncore,
+						       GEN10_FREQ_INFO_REC));
+		else
 			caps->rp1_freq = (rp_state_cap >>  8) & 0xff;
 		caps->min_freq = (rp_state_cap >> 16) & 0xff;
 	}

drivers/gpu/drm/i915/gt/selftest_slpc.c

@@ -166,6 +166,15 @@ static int run_test(struct intel_gt *gt, int test_type)
 		return -EIO;
 	}
 
+	/*
+	 * FIXME: With efficient frequency enabled, GuC can request
+	 * frequencies higher than the SLPC max. While this is fixed
+	 * in GuC, we level set these tests with RPn as min.
+	 */
+	err = slpc_set_min_freq(slpc, slpc->min_freq);
+	if (err)
+		return err;
+
 	if (slpc->min_freq == slpc->rp0_freq) {
 		pr_err("Min/Max are fused to the same value\n");
 		return -EINVAL;

drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c

@@ -137,17 +137,6 @@ static int guc_action_slpc_set_param(struct intel_guc *guc, u8 id, u32 value)
 	return ret > 0 ? -EPROTO : ret;
 }
 
-static int guc_action_slpc_unset_param(struct intel_guc *guc, u8 id)
-{
-	u32 request[] = {
-		GUC_ACTION_HOST2GUC_PC_SLPC_REQUEST,
-		SLPC_EVENT(SLPC_EVENT_PARAMETER_UNSET, 1),
-		id,
-	};
-
-	return intel_guc_send(guc, request, ARRAY_SIZE(request));
-}
-
 static bool slpc_is_running(struct intel_guc_slpc *slpc)
 {
 	return slpc_get_state(slpc) == SLPC_GLOBAL_STATE_RUNNING;
@@ -201,16 +190,6 @@ static int slpc_set_param(struct intel_guc_slpc *slpc, u8 id, u32 value)
 	return ret;
 }
 
-static int slpc_unset_param(struct intel_guc_slpc *slpc,
-			    u8 id)
-{
-	struct intel_guc *guc = slpc_to_guc(slpc);
-
-	GEM_BUG_ON(id >= SLPC_MAX_PARAM);
-
-	return guc_action_slpc_unset_param(guc, id);
-}
-
 static int slpc_force_min_freq(struct intel_guc_slpc *slpc, u32 freq)
 {
 	struct drm_i915_private *i915 = slpc_to_i915(slpc);
@@ -491,6 +470,16 @@ int intel_guc_slpc_set_min_freq(struct intel_guc_slpc *slpc, u32 val)
 
 	with_intel_runtime_pm(&i915->runtime_pm, wakeref) {
 
+		/* Ignore efficient freq if lower min freq is requested */
+		ret = slpc_set_param(slpc,
+				     SLPC_PARAM_IGNORE_EFFICIENT_FREQUENCY,
+				     val < slpc->rp1_freq);
+		if (unlikely(ret)) {
+			i915_probe_error(i915, "Failed to toggle efficient freq (%pe)\n",
+					 ERR_PTR(ret));
+			return ret;
+		}
+
 		ret = slpc_set_param(slpc,
 				     SLPC_PARAM_GLOBAL_MIN_GT_UNSLICE_FREQ_MHZ,
 				     val);
@@ -587,7 +576,9 @@ static int slpc_set_softlimits(struct intel_guc_slpc *slpc)
 		return ret;
 
 	if (!slpc->min_freq_softlimit) {
-		slpc->min_freq_softlimit = slpc->min_freq;
+		ret = intel_guc_slpc_get_min_freq(slpc, &slpc->min_freq_softlimit);
+		if (unlikely(ret))
+			return ret;
 		slpc_to_gt(slpc)->defaults.min_freq = slpc->min_freq_softlimit;
 	} else if (slpc->min_freq_softlimit != slpc->min_freq) {
 		return intel_guc_slpc_set_min_freq(slpc,
@@ -597,29 +588,6 @@ static int slpc_set_softlimits(struct intel_guc_slpc *slpc)
 	return 0;
 }
 
-static int slpc_ignore_eff_freq(struct intel_guc_slpc *slpc, bool ignore)
-{
-	int ret = 0;
-
-	if (ignore) {
-		ret = slpc_set_param(slpc,
-				     SLPC_PARAM_IGNORE_EFFICIENT_FREQUENCY,
-				     ignore);
-		if (!ret)
-			return slpc_set_param(slpc,
-					      SLPC_PARAM_GLOBAL_MIN_GT_UNSLICE_FREQ_MHZ,
-					      slpc->min_freq);
-	} else {
-		ret = slpc_unset_param(slpc,
-				       SLPC_PARAM_IGNORE_EFFICIENT_FREQUENCY);
-		if (!ret)
-			return slpc_unset_param(slpc,
-						SLPC_PARAM_GLOBAL_MIN_GT_UNSLICE_FREQ_MHZ);
-	}
-
-	return ret;
-}
-
 static int slpc_use_fused_rp0(struct intel_guc_slpc *slpc)
 {
 	/* Force SLPC to used platform rp0 */
@@ -679,14 +647,6 @@ int intel_guc_slpc_enable(struct intel_guc_slpc *slpc)
 
 	slpc_get_rp_values(slpc);
 
-	/* Ignore efficient freq and set min to platform min */
-	ret = slpc_ignore_eff_freq(slpc, true);
-	if (unlikely(ret)) {
-		i915_probe_error(i915, "Failed to set SLPC min to RPn (%pe)\n",
-				 ERR_PTR(ret));
-		return ret;
-	}
-
 	/* Set SLPC max limit to RP0 */
 	ret = slpc_use_fused_rp0(slpc);
 	if (unlikely(ret)) {

drivers/gpu/drm/i915/intel_mchbar_regs.h

@@ -196,6 +196,9 @@
 #define   RP1_CAP_MASK				REG_GENMASK(15, 8)
 #define   RPN_CAP_MASK				REG_GENMASK(23, 16)
 
+#define GEN10_FREQ_INFO_REC			_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x5ef0)
+#define   RPE_MASK				REG_GENMASK(15, 8)
+
 /* snb MCH registers for priority tuning */
 #define MCH_SSKPD				_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x5d10)
 #define   SSKPD_NEW_WM0_MASK_HSW		REG_GENMASK64(63, 56)