[S] Change in coreboot[main]: arch/x86/cpu_common: Add cpu_get_c_state_support

[Patrick Rudolph (Code Review)]

Patrick Rudolph has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/78224?usp=email )

Change subject: arch/x86/cpu_common: Add cpu_get_c_state_support
......................................................................

arch/x86/cpu_common: Add cpu_get_c_state_support

Add a function to get the number of substates supported by
an Intel CPU C-state.

Test: Can read out the supported C-state substates.

Change-Id: Ie57e87609ea5d6ec6f37154e8b84f1e9574aa4a9
Signed-off-by: Patrick Rudolph 
---
M src/arch/x86/cpu_common.c
M src/arch/x86/include/arch/cpu.h
2 files changed, 30 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/24/78224/1

diff --git a/src/arch/x86/cpu_common.c b/src/arch/x86/cpu_common.c
index 9387f3b..f18b501 100644
--- a/src/arch/x86/cpu_common.c
+++ b/src/arch/x86/cpu_common.c
@@ -187,6 +187,23 @@
    return info->num_ways * info->physical_partitions * info->line_size * info->num_sets;
 }

+/*
+ * Returns the sub-states supported by the specified CPU
+ * C-state level.
+ *
+ * Level 0 corresponds to the lowest C-state (C0).
+ * Higher levels are processor specific.
+ */
+uint8_t cpu_get_c_substate_support(const int state)
+{
+	if ((cpuid_get_max_func() < 5) ||
+	    !(cpuid_ecx(5) & CPUID_FEATURE_MONITOR_MWAIT) ||
+	    (state > 4))
+		return 0;
+
+	return (cpuid_edx(5) >> (state * 4)) & 0xf;
+}
+
 bool fill_cpu_cache_info(uint8_t level, struct cpu_cache_info *info)
 {
    if (!info)
diff --git a/src/arch/x86/include/arch/cpu.h b/src/arch/x86/include/arch/cpu.h
index 2c98d1e..f9517af 100644
--- a/src/arch/x86/include/arch/cpu.h
+++ b/src/arch/x86/include/arch/cpu.h
@@ -99,6 +99,10 @@
 #define CPUID_CACHE_NO_OF_SETS_MASK 0xffffffff
 #define CPUID_CACHE_NO_OF_SETS(res) CPUID_CACHE(NO_OF_SETS, (res).ecx)

+// Intel leaf 0x5
+#define CPUID_FEATURE_MONITOR_MWAIT		(1 << 0)
+#define CPUID_FEATURE_INTERUPT_BREAK_EVENT	(1 << 1)
+
 unsigned int cpu_cpuid_extended_level(void);
 int cpu_have_cpuid(void);

@@ -311,6 +315,15 @@
 size_t get_cache_size(const struct cpu_cache_info *info);

/*
+ * Returns the sub-states supported by the specified CPU
+ * C-state level.
+ *
+ * Level 0 corresponds to the lowest C-state (C0).
+ * Higher levels are processor specific.
+ */
+uint8_t cpu_get_c_substate_support(const int lvl);
+
+/*
  * fill_cpu_cache_info to get all required cache info data and fill into cpu_cache_info
  * structure by calling CPUID.EAX=leaf and ECX=Cache Level.
  */