cpufreq: intel_pstate: get P1 from TAR when available

After Ivybridge, the max non turbo ratio obtained from platform info msr
is not always guaranteed P1 on client platforms. The max non turbo
activation ratio (TAR), determines the max for the current level of TDP.
The ratio in platform info is physical max. The TAR MSR can be locked,
so updating this value is not possible on all platforms.
This change gets this ratio from MSR TURBO_ACTIVATION_RATIO if
available,
but also do some sanity checking to make sure that this value is
correct.
The sanity check involves reading the TDP ratio for the current tdp
control value when platform has configurable TDP present and matching
TAC
with this.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Acked-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 35 insertions, 4 deletions

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 3af9dd7332e6..da92d0201d52 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -43,7 +43,6 @@
 #define int_tofp(X) ((int64_t)(X) << FRAC_BITS)
 #define fp_toint(X) ((X) >> FRAC_BITS)
 
-
 static inline int32_t mul_fp(int32_t x, int32_t y)
 {
 	return ((int64_t)x * (int64_t)y) >> FRAC_BITS;
@@ -593,10 +592,42 @@ static int core_get_min_pstate(void)
 
 static int core_get_max_pstate(void)
 {
-	u64 value;
+	u64 tar;
+	u64 plat_info;
+	int max_pstate;
+	int err;
+
+	rdmsrl(MSR_PLATFORM_INFO, plat_info);
+	max_pstate = (plat_info >> 8) & 0xFF;
+
+	err = rdmsrl_safe(MSR_TURBO_ACTIVATION_RATIO, &tar);
+	if (!err) {
+		/* Do some sanity checking for safety */
+		if (plat_info & 0x600000000) {
+			u64 tdp_ctrl;
+			u64 tdp_ratio;
+			int tdp_msr;
+
+			err = rdmsrl_safe(MSR_CONFIG_TDP_CONTROL, &tdp_ctrl);
+			if (err)
+				goto skip_tar;
+
+			tdp_msr = MSR_CONFIG_TDP_NOMINAL + tdp_ctrl;
+			err = rdmsrl_safe(tdp_msr, &tdp_ratio);
+			if (err)
+				goto skip_tar;
+
+			if (tdp_ratio - 1 == tar) {
+				max_pstate = tar;
+				pr_debug("max_pstate=TAC %x\n", max_pstate);
+			} else {
+				goto skip_tar;
+			}
+		}
+	}
 
-	rdmsrl(MSR_PLATFORM_INFO, value);
-	return (value >> 8) & 0xFF;
+skip_tar:
+	return max_pstate;
 }
 
 static int core_get_turbo_pstate(void)