drm/i915/slpc: Let's fix the PCODE min freq table setup for SLPC

We need to inform PCODE of a desired ring frequencies so PCODE update
the memory frequencies to us. rps->min_freq and rps->max_freq are the
frequencies used in that request. However they were unset when SLPC was
enabled and PCODE never updated the memory freq.

v2 (as Suggested by Ashutosh): if SLPC is in use, let's pick the right
   frequencies from the get_ia_constants instead of the fake init of
   rps' min and max.

v3: don't forget the max <= min return

v4: Move all the freq conversion to intel_rps.c. And the max <= min
    check to where it belongs.

v5: (Ashutosh) Fix old comment s/50 HZ/50 MHz and add a doc explaining
    the "raw format"

Fixes: 7ba79a6715 ("drm/i915/guc/slpc: Gate Host RPS when SLPC is enabled")
Cc: <stable@vger.kernel.org> # v5.15+
Cc: Ashutosh Dixit <ashutosh.dixit@intel.com>
Tested-by: Sushma Venkatesh Reddy <sushma.venkatesh.reddy@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220831214538.143950-1-rodrigo.vivi@intel.com

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

@@ -12,6 +12,7 @@
 #include "intel_llc.h"
 #include "intel_mchbar_regs.h"
 #include "intel_pcode.h"
+#include "intel_rps.h"
 
 struct ia_constants {
 	unsigned int min_gpu_freq;
@@ -55,9 +56,6 @@ static bool get_ia_constants(struct intel_llc *llc,
 	if (!HAS_LLC(i915) || IS_DGFX(i915))
 		return false;
 
-	if (rps->max_freq <= rps->min_freq)
-		return false;
-
 	consts->max_ia_freq = cpu_max_MHz();
 
 	consts->min_ring_freq =
@@ -65,13 +63,8 @@ static bool get_ia_constants(struct intel_llc *llc,
 	/* convert DDR frequency from units of 266.6MHz to bandwidth */
 	consts->min_ring_freq = mult_frac(consts->min_ring_freq, 8, 3);
 
-	consts->min_gpu_freq = rps->min_freq;
-	consts->max_gpu_freq = rps->max_freq;
-	if (GRAPHICS_VER(i915) >= 9) {
-		/* Convert GT frequency to 50 HZ units */
-		consts->min_gpu_freq /= GEN9_FREQ_SCALER;
-		consts->max_gpu_freq /= GEN9_FREQ_SCALER;
-	}
+	consts->min_gpu_freq = intel_rps_get_min_raw_freq(rps);
+	consts->max_gpu_freq = intel_rps_get_max_raw_freq(rps);
 
 	return true;
 }
@@ -130,6 +123,12 @@ static void gen6_update_ring_freq(struct intel_llc *llc)
 	if (!get_ia_constants(llc, &consts))
 		return;
 
+	/*
+	 * Although this is unlikely on any platform during initialization,
+	 * let's ensure we don't get accidentally into infinite loop
+	 */
+	if (consts.max_gpu_freq <= consts.min_gpu_freq)
+		return;
 	/*
 	 * For each potential GPU frequency, load a ring frequency we'd like
 	 * to use for memory access.  We do this by specifying the IA frequency

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

@@ -2133,6 +2133,31 @@ u32 intel_rps_get_max_frequency(struct intel_rps *rps)
 		return intel_gpu_freq(rps, rps->max_freq_softlimit);
 }
 
+/**
+ * intel_rps_get_max_raw_freq - returns the max frequency in some raw format.
+ * @rps: the intel_rps structure
+ *
+ * Returns the max frequency in a raw format. In newer platforms raw is in
+ * units of 50 MHz.
+ */
+u32 intel_rps_get_max_raw_freq(struct intel_rps *rps)
+{
+	struct intel_guc_slpc *slpc = rps_to_slpc(rps);
+	u32 freq;
+
+	if (rps_uses_slpc(rps)) {
+		return DIV_ROUND_CLOSEST(slpc->rp0_freq,
+					 GT_FREQUENCY_MULTIPLIER);
+	} else {
+		freq = rps->max_freq;
+		if (GRAPHICS_VER(rps_to_i915(rps)) >= 9) {
+			/* Convert GT frequency to 50 MHz units */
+			freq /= GEN9_FREQ_SCALER;
+		}
+		return freq;
+	}
+}
+
 u32 intel_rps_get_rp0_frequency(struct intel_rps *rps)
 {
 	struct intel_guc_slpc *slpc = rps_to_slpc(rps);
@@ -2221,6 +2246,31 @@ u32 intel_rps_get_min_frequency(struct intel_rps *rps)
 		return intel_gpu_freq(rps, rps->min_freq_softlimit);
 }
 
+/**
+ * intel_rps_get_min_raw_freq - returns the min frequency in some raw format.
+ * @rps: the intel_rps structure
+ *
+ * Returns the min frequency in a raw format. In newer platforms raw is in
+ * units of 50 MHz.
+ */
+u32 intel_rps_get_min_raw_freq(struct intel_rps *rps)
+{
+	struct intel_guc_slpc *slpc = rps_to_slpc(rps);
+	u32 freq;
+
+	if (rps_uses_slpc(rps)) {
+		return DIV_ROUND_CLOSEST(slpc->min_freq,
+					 GT_FREQUENCY_MULTIPLIER);
+	} else {
+		freq = rps->min_freq;
+		if (GRAPHICS_VER(rps_to_i915(rps)) >= 9) {
+			/* Convert GT frequency to 50 MHz units */
+			freq /= GEN9_FREQ_SCALER;
+		}
+		return freq;
+	}
+}
+
 static int set_min_freq(struct intel_rps *rps, u32 val)
 {
 	int ret = 0;

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

@@ -37,8 +37,10 @@ u32 intel_rps_get_cagf(struct intel_rps *rps, u32 rpstat1);
 u32 intel_rps_read_actual_frequency(struct intel_rps *rps);
 u32 intel_rps_get_requested_frequency(struct intel_rps *rps);
 u32 intel_rps_get_min_frequency(struct intel_rps *rps);
+u32 intel_rps_get_min_raw_freq(struct intel_rps *rps);
 int intel_rps_set_min_frequency(struct intel_rps *rps, u32 val);
 u32 intel_rps_get_max_frequency(struct intel_rps *rps);
+u32 intel_rps_get_max_raw_freq(struct intel_rps *rps);
 int intel_rps_set_max_frequency(struct intel_rps *rps, u32 val);
 u32 intel_rps_get_rp0_frequency(struct intel_rps *rps);
 u32 intel_rps_get_rp1_frequency(struct intel_rps *rps);