[CPUFREQ] powernow-k8: determine exact CPU frequency for HW Pstates
Slightly modified by trenn@suse.de -> only do this on fam 10h and fam 11h.
Currently powernow-k8 determines CPU frequency from ACPI PSS objects, but
according to AMD family 11h BKDG this frequency is just a rounded value:
"CoreFreq (MHz) = The CPU COF specified by MSRC001_00[6B:64][CpuFid]
rounded to the nearest 100 Mhz."
As a consequnce powernow-k8 reports wrong CPU frequency on some systems,
e.g. on Turion X2 Ultra:
powernow-k8: Found 1 AMD Turion(tm)X2 Ultra DualCore Mobile ZM-82
processors (2 cpu cores) (version 2.20.00)
powernow-k8: 0 : pstate 0 (2200 MHz)
powernow-k8: 1 : pstate 1 (1100 MHz)
powernow-k8: 2 : pstate 2 (600 MHz)
But this is wrong as frequency for Pstate2 is 550 MHz. x86info reports it
correctly:
#x86info -a |grep Pstate
...
Pstate-0: fid=e, did=0, vid=24 (2200MHz)
Pstate-1: fid=e, did=1, vid=30 (1100MHz)
Pstate-2: fid=e, did=2, vid=3c (550MHz) (current)
Solution is to determine the frequency directly from Pstate MSRs instead
of using rounded values from ACPI table.
Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Dave Jones <davej@redhat.com>
diff --git a/arch/x86/kernel/cpu/cpufreq/powernow-k8.c b/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
index feef10c..f6b32d1 100644
--- a/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
+++ b/arch/x86/kernel/cpu/cpufreq/powernow-k8.c
@@ -649,6 +649,20 @@
data->batps);
}
+static u32 freq_from_fid_did(u32 fid, u32 did)
+{
+ u32 mhz = 0;
+
+ if (boot_cpu_data.x86 == 0x10)
+ mhz = (100 * (fid + 0x10)) >> did;
+ else if (boot_cpu_data.x86 == 0x11)
+ mhz = (100 * (fid + 8)) >> did;
+ else
+ BUG();
+
+ return mhz * 1000;
+}
+
static int fill_powernow_table(struct powernow_k8_data *data,
struct pst_s *pst, u8 maxvid)
{
@@ -923,8 +937,13 @@
powernow_table[i].index = index;
- powernow_table[i].frequency =
- data->acpi_data.states[i].core_frequency * 1000;
+ /* Frequency may be rounded for these */
+ if (boot_cpu_data.x86 == 0x10 || boot_cpu_data.x86 == 0x11) {
+ powernow_table[i].frequency =
+ freq_from_fid_did(lo & 0x3f, (lo >> 6) & 7);
+ } else
+ powernow_table[i].frequency =
+ data->acpi_data.states[i].core_frequency * 1000;
}
return 0;
}
