drm/i915/gt: Extract per-platform function for frequency read

Instead of calling read_clock_frequency() to walk the if/else ladder
per platform, move the ladder to intel_gt_init_clock_frequency() and
use one function per branch.

With the new logic, it's now clear the call to
gen9_get_crystal_clock_freq() was just dead code, as gen9 is handled by
another function and there is no version 10. Remove that function and
the caller.

v2: Correctly handle intel_gt_check_clock_frequency() that also calls
the function to read clock frequency (Gustavo)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220908-if-ladder-v2-2-7a7b15545c93@intel.com

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

@@ -26,26 +26,6 @@ static u32 read_reference_ts_freq(struct intel_uncore *uncore)
 	return base_freq + frac_freq;
 }
 
-static u32 gen9_get_crystal_clock_freq(struct intel_uncore *uncore,
-				       u32 rpm_config_reg)
-{
-	u32 f19_2_mhz = 19200000;
-	u32 f24_mhz = 24000000;
-	u32 crystal_clock =
-		(rpm_config_reg & GEN9_RPM_CONFIG0_CRYSTAL_CLOCK_FREQ_MASK) >>
-		GEN9_RPM_CONFIG0_CRYSTAL_CLOCK_FREQ_SHIFT;
-
-	switch (crystal_clock) {
-	case GEN9_RPM_CONFIG0_CRYSTAL_CLOCK_FREQ_19_2_MHZ:
-		return f19_2_mhz;
-	case GEN9_RPM_CONFIG0_CRYSTAL_CLOCK_FREQ_24_MHZ:
-		return f24_mhz;
-	default:
-		MISSING_CASE(crystal_clock);
-		return 0;
-	}
-}
-
 static u32 gen11_get_crystal_clock_freq(struct intel_uncore *uncore,
 					u32 rpm_config_reg)
 {
@@ -72,17 +52,15 @@ static u32 gen11_get_crystal_clock_freq(struct intel_uncore *uncore,
 	}
 }
 
-static u32 read_clock_frequency(struct intel_uncore *uncore)
+static u32 gen11_read_clock_frequency(struct intel_uncore *uncore)
 {
-	u32 f12_5_mhz = 12500000;
-	u32 f19_2_mhz = 19200000;
-	u32 f24_mhz = 24000000;
-
-	if (GRAPHICS_VER(uncore->i915) >= 11) {
 	u32 ctc_reg = intel_uncore_read(uncore, CTC_MODE);
 	u32 freq = 0;
 
 	/*
+	 * Note that on gen11+, the clock frequency may be reconfigured.
+	 * We do not, and we assume nobody else does.
+	 *
 	 * First figure out the reference frequency. There are 2 ways
 	 * we can compute the frequency, either through the
 	 * TIMESTAMP_OVERRIDE register or through RPM_CONFIG. CTC_MODE
@@ -93,10 +71,7 @@ static u32 read_clock_frequency(struct intel_uncore *uncore)
 	} else {
 		u32 c0 = intel_uncore_read(uncore, RPM_CONFIG0);
 
-			if (GRAPHICS_VER(uncore->i915) >= 11)
 		freq = gen11_get_crystal_clock_freq(uncore, c0);
-			else
-				freq = gen9_get_crystal_clock_freq(uncore, c0);
 
 		/*
 		 * Now figure out how the command stream's timestamp
@@ -108,14 +83,17 @@ static u32 read_clock_frequency(struct intel_uncore *uncore)
 	}
 
 	return freq;
-	} else if (GRAPHICS_VER(uncore->i915) >= 9) {
+}
+
+static u32 gen9_read_clock_frequency(struct intel_uncore *uncore)
+{
 	u32 ctc_reg = intel_uncore_read(uncore, CTC_MODE);
 	u32 freq = 0;
 
 	if ((ctc_reg & CTC_SOURCE_PARAMETER_MASK) == CTC_SOURCE_DIVIDE_LOGIC) {
 		freq = read_reference_ts_freq(uncore);
 	} else {
-			freq = IS_GEN9_LP(uncore->i915) ? f19_2_mhz : f24_mhz;
+		freq = IS_GEN9_LP(uncore->i915) ? 19200000 : 24000000;
 
 		/*
 		 * Now figure out how the command stream's timestamp
@@ -127,7 +105,10 @@ static u32 read_clock_frequency(struct intel_uncore *uncore)
 	}
 
 	return freq;
-	} else if (GRAPHICS_VER(uncore->i915) >= 5) {
+}
+
+static u32 gen5_read_clock_frequency(struct intel_uncore *uncore)
+{
 	/*
 	 * PRMs say:
 	 *
@@ -135,8 +116,11 @@ static u32 read_clock_frequency(struct intel_uncore *uncore)
 	 *      reflects bits 38:3 of the TSC (i.e. 80ns granularity,
 	 *      rolling over every 1.5 hours).
 	 */
-		return f12_5_mhz;
-	} else {
+	return 12500000;
+}
+
+static u32 gen2_read_clock_frequency(struct intel_uncore *uncore)
+{
 	/*
 	 * PRMs say:
 	 *
@@ -145,22 +129,29 @@ static u32 read_clock_frequency(struct intel_uncore *uncore)
 	 *      (“CLKCFG”) MCHBAR register)
 	 */
 	return RUNTIME_INFO(uncore->i915)->rawclk_freq * 1000 / 16;
-	}
+}
+
+static u32 read_clock_frequency(struct intel_uncore *uncore)
+{
+	if (GRAPHICS_VER(uncore->i915) >= 11)
+		return gen11_read_clock_frequency(uncore);
+	else if (GRAPHICS_VER(uncore->i915) >= 9)
+		return gen9_read_clock_frequency(uncore);
+	else if (GRAPHICS_VER(uncore->i915) >= 5)
+		return gen5_read_clock_frequency(uncore);
+	else
+		return gen2_read_clock_frequency(uncore);
 }
 
 void intel_gt_init_clock_frequency(struct intel_gt *gt)
 {
-	/*
-	 * Note that on gen11+, the clock frequency may be reconfigured.
-	 * We do not, and we assume nobody else does.
-	 */
 	gt->clock_frequency = read_clock_frequency(gt->uncore);
-	if (gt->clock_frequency)
-		gt->clock_period_ns = intel_gt_clock_interval_to_ns(gt, 1);
 
 	/* Icelake appears to use another fixed frequency for CTX_TIMESTAMP */
 	if (GRAPHICS_VER(gt->i915) == 11)
 		gt->clock_period_ns = NSEC_PER_SEC / 13750000;
+	else if (gt->clock_frequency)
+		gt->clock_period_ns = intel_gt_clock_interval_to_ns(gt, 1);
 
 	GT_TRACE(gt,
 		 "Using clock frequency: %dkHz, period: %dns, wrap: %lldms\n",