[PATCH] drm/i915/slpc: Use platform limits for min/max frequency

[Vinay Belgaumkar <vinay.belgaumkar@xxxxxxxxx>]

GuC will set the min/max frequencies to theoretical max on
ATS-M. This will break kernel ABI, so limit min/max frequency
to RP0(platform max) instead.

Also modify the SLPC selftest to update the min frequency
when we have a server part so that we can iterate between
platform min and max.

Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@xxxxxxxxx>
---
 drivers/gpu/drm/i915/gt/selftest_slpc.c       | 40 +++++++++++++------
 drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c   | 29 ++++++++++++++
 .../gpu/drm/i915/gt/uc/intel_guc_slpc_types.h |  3 ++
 3 files changed, 60 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/selftest_slpc.c b/drivers/gpu/drm/i915/gt/selftest_slpc.c
index 4c6e9257e593..1f84362af737 100644
--- a/drivers/gpu/drm/i915/gt/selftest_slpc.c
+++ b/drivers/gpu/drm/i915/gt/selftest_slpc.c
@@ -234,6 +234,7 @@ static int run_test(struct intel_gt *gt, int test_type)
 	enum intel_engine_id id;
 	struct igt_spinner spin;
 	u32 slpc_min_freq, slpc_max_freq;
+	u32 saved_min_freq;
 	int err = 0;
 
 	if (!intel_uc_uses_guc_slpc(&gt->uc))
@@ -252,20 +253,35 @@ 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;
+		/* Servers will have min/max clamped to RP0 */
+		if (slpc->min_is_rpmax) {
+			err = slpc_set_min_freq(slpc, slpc->min_freq);
+			if (err) {
+				pr_err("Unable to update min freq on server part");
+				return err;
+			}
+
+		} else {
+			pr_err("Min/Max are fused to the same value\n");
+			return -EINVAL;
+		}
+	} else {
+		/*
+		 * 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;
 	}
 
+	saved_min_freq = slpc_min_freq;
+
+	/* New temp min freq = RPn */
+	slpc_min_freq = slpc->min_freq;
+
 	intel_gt_pm_wait_for_idle(gt);
 	intel_gt_pm_get(gt);
 	for_each_engine(engine, gt, id) {
@@ -347,7 +363,7 @@ static int run_test(struct intel_gt *gt, int test_type)
 
 	/* Restore min/max frequencies */
 	slpc_set_max_freq(slpc, slpc_max_freq);
-	slpc_set_min_freq(slpc, slpc_min_freq);
+	slpc_set_min_freq(slpc, saved_min_freq);
 
 	if (igt_flush_test(gt->i915))
 		err = -EIO;
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 fdd895f73f9f..11613d373a49 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c
@@ -263,6 +263,7 @@ int intel_guc_slpc_init(struct intel_guc_slpc *slpc)
 
 	slpc->max_freq_softlimit = 0;
 	slpc->min_freq_softlimit = 0;
+	slpc->min_is_rpmax = false;
 
 	slpc->boost_freq = 0;
 	atomic_set(&slpc->num_waiters, 0);
@@ -588,6 +589,31 @@ static int slpc_set_softlimits(struct intel_guc_slpc *slpc)
 	return 0;
 }
 
+static bool is_slpc_min_freq_rpmax(struct intel_guc_slpc *slpc)
+{
+	int slpc_min_freq;
+
+	if (intel_guc_slpc_get_min_freq(slpc, &slpc_min_freq))
+		return false;
+
+	if (slpc_min_freq > slpc->rp0_freq)
+		return true;
+	else
+		return false;
+}
+
+static void update_server_min_softlimit(struct intel_guc_slpc *slpc)
+{
+	/* For server parts, SLPC min will be at RPMax.
+	 * Use min softlimit to clamp it to RP0 instead.
+	 */
+	if (is_slpc_min_freq_rpmax(slpc) &&
+	    !slpc->min_freq_softlimit) {
+		slpc->min_is_rpmax = true;
+		slpc->min_freq_softlimit = slpc->rp0_freq;
+	}
+}
+
 static int slpc_use_fused_rp0(struct intel_guc_slpc *slpc)
 {
 	/* Force SLPC to used platform rp0 */
@@ -647,6 +673,9 @@ int intel_guc_slpc_enable(struct intel_guc_slpc *slpc)
 
 	slpc_get_rp_values(slpc);
 
+	/* Handle the case where min=max=RPmax */
+	update_server_min_softlimit(slpc);
+
 	/* Set SLPC max limit to RP0 */
 	ret = slpc_use_fused_rp0(slpc);
 	if (unlikely(ret)) {
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_slpc_types.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_slpc_types.h
index 73d208123528..a6ef53b04e04 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_slpc_types.h
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_slpc_types.h
@@ -19,6 +19,9 @@ struct intel_guc_slpc {
 	bool supported;
 	bool selected;
 
+	/* Indicates this is a server part */
+	bool min_is_rpmax;
+
 	/* platform frequency limits */
 	u32 min_freq;
 	u32 rp0_freq;
-- 
2.35.1