soc/intel/common/block/acpi: fix P-States extra entry

The ratio_max step is appearing twice when (ratio_max - ratio_min)
is evenly divisible by the ratio step.

This is because in this case there are no rounding down of ratio_max in
the for loop.

Thanks Jay Talbott for the step calculation algorithm.

Change-Id: I91090b4d87eb82b57055c24271d679d1cbb3b7a7
Signed-off-by: Julien Viard de Galbert <jviarddegalbert@online.net>
Reviewed-on: https://review.coreboot.org/c/25429
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

1 files changed, 16 insertions, 10 deletions

diff --git a/src/soc/intel/common/block/acpi/acpi.c b/src/soc/intel/common/block/acpi/acpi.c
index 0ea6cb9d70..21d877b162 100644
--- a/src/soc/intel/common/block/acpi/acpi.c
+++ b/src/soc/intel/common/block/acpi/acpi.c
@@ -299,11 +299,13 @@ void generate_p_state_entries(int core, int cores_per_package)
 	int ratio_min, ratio_max, ratio_turbo, ratio_step;
 	int coord_type, power_max, num_entries;
 	int ratio, power, clock, clock_max;
+	bool turbo;
 
 	coord_type = cpu_get_coord_type();
 	ratio_min = cpu_get_min_ratio();
 	ratio_max = cpu_get_max_ratio();
 	clock_max = (ratio_max * cpu_get_bus_clock()) / KHz;
+	turbo = (get_turbo_state() == TURBO_ENABLED);
 
 	/* Calculate CPU TDP in mW */
 	power_max = cpu_get_power_max();
@@ -321,16 +323,21 @@ void generate_p_state_entries(int core, int cores_per_package)
 
 	/* Determine ratio points */
 	ratio_step = PSS_RATIO_STEP;
-	num_entries = ((ratio_max - ratio_min) / ratio_step) + 1;
-	if (num_entries > PSS_MAX_ENTRIES) {
-		ratio_step += 1;
+	do {
 		num_entries = ((ratio_max - ratio_min) / ratio_step) + 1;
-	}
+		if (((ratio_max - ratio_min) % ratio_step) > 0)
+			num_entries += 1;
+		if (turbo)
+			num_entries += 1;
+		if (num_entries > PSS_MAX_ENTRIES)
+			ratio_step += 1;
+	} while (num_entries > PSS_MAX_ENTRIES);
+
+	/* _PSS package count depends on Turbo */
+	acpigen_write_package(num_entries);
 
 	/* P[T] is Turbo state if enabled */
-	if (get_turbo_state() == TURBO_ENABLED) {
-		/* _PSS package count including Turbo */
-		acpigen_write_package(num_entries + 2);
+	if (turbo) {
 		ratio_turbo = cpu_get_max_turbo_ratio();
 
 		/* Add entry for Turbo ratio */
@@ -340,9 +347,7 @@ void generate_p_state_entries(int core, int cores_per_package)
 					  PSS_LATENCY_BUSMASTER,/* lat2 */
 					  ratio_turbo << 8,	/* control */
 					  ratio_turbo << 8);	/* status */
-	} else {
-		/* _PSS package count without Turbo */
-		acpigen_write_package(num_entries + 1);
+		num_entries -= 1;
 	}
 
 	/* First regular entry is max non-turbo ratio */
@@ -352,6 +357,7 @@ void generate_p_state_entries(int core, int cores_per_package)
 				  PSS_LATENCY_BUSMASTER,/* lat2 */
 				  ratio_max << 8,	/* control */
 				  ratio_max << 8);	/* status */
+	num_entries -= 1;
 
 	/* Generate the remaining entries */
 	for (ratio = ratio_min + ((num_entries - 1) * ratio_step);