[PATCH v4 07/15] xen/cpufreq: fix core frequency calculation for AMD Family 1Ah CPUs

[Penny Zheng <Penny.Zheng@xxxxxxx>]

AMD Family 1Ah CPU needs a different COF(Core Operating Frequency) formula,
due to a change in the PStateDef MSR layout in AMD Family 1Ah.
In AMD Family 1Ah, Core current operating frequency in MHz is calculated as
follows:
    CoreCOF = Core::X86::Msr::PStateDef[CpuFid[11:0]] * 5MHz

We introduce a helper amd_parse_freq() to parse cpu min/nominal/max core
frequency from PstateDef register, to replace the original macro FREQ(v).
amd_parse_freq() is declared as const, as it mainly consists of mathematical
conputation.

Signed-off-by: Penny Zheng <Penny.Zheng@xxxxxxx>
---
v2 -> v3:
- new commit
---
v3 -> v4:
 - introduce amd_parse_freq() and declare it as const
 - express if-else-arry() as switch()
---
 xen/arch/x86/cpu/amd.c | 43 +++++++++++++++++++++++++++++++++++-------
 1 file changed, 36 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/cpu/amd.c b/xen/arch/x86/cpu/amd.c
index ce4e1df710..f93dda927e 100644
--- a/xen/arch/x86/cpu/amd.c
+++ b/xen/arch/x86/cpu/amd.c
@@ -56,6 +56,9 @@ bool __initdata amd_virt_spec_ctrl;
 
 static bool __read_mostly fam17_c6_disabled;
 
+static uint64_t attr_const amd_parse_freq(unsigned char c, uint64_t value);
+#define INVAL_FREQ_MHZ  ~(uint64_t)0
+
 static inline int rdmsr_amd_safe(unsigned int msr, unsigned int *lo,
                                 unsigned int *hi)
 {
@@ -570,12 +573,35 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
                                                           : c->cpu_core_id);
 }
 
+static uint64_t amd_parse_freq(unsigned char c, uint64_t value)
+{
+       uint64_t freq = INVAL_FREQ_MHZ;
+
+       switch (c) {
+       case 0x10 ... 0x16:
+               freq = (((value & 0x3f) + 0x10) * 100) >> ((value >> 6) & 7);
+               break;
+       case 0x17 ... 0x19:
+               freq = ((value & 0xff) * 25 * 8) / ((value >> 8) & 0x3f);
+               break;
+       case 0x1A:
+               freq = (value & 0xfff) * 5;
+               break;
+       default:
+               printk(XENLOG_ERR
+                      "Unsupported cpu familly %c on cpufreq parsing", c);
+               break;
+       }
+
+       return freq;
+}
+
 void amd_log_freq(const struct cpuinfo_x86 *c)
 {
        unsigned int idx = 0, h;
        uint64_t hi, lo, val;
 
-       if (c->x86 < 0x10 || c->x86 > 0x19 ||
+       if (c->x86 < 0x10 || c->x86 > 0x1A ||
            (c != &boot_cpu_data &&
             (!opt_cpu_info || (c->apicid & (c->x86_num_siblings - 1)))))
                return;
@@ -656,19 +682,22 @@ void amd_log_freq(const struct cpuinfo_x86 *c)
        if (!(lo >> 63))
                return;
 
-#define FREQ(v) (c->x86 < 0x17 ? ((((v) & 0x3f) + 0x10) * 100) >> (((v) >> 6) 
& 7) \
-                                    : (((v) & 0xff) * 25 * 8) / (((v) >> 8) & 
0x3f))
        if (idx && idx < h &&
            !rdmsr_safe(0xC0010064 + idx, val) && (val >> 63) &&
            !rdmsr_safe(0xC0010064, hi) && (hi >> 63))
                printk("CPU%u: %lu (%lu ... %lu) MHz\n",
-                      smp_processor_id(), FREQ(val), FREQ(lo), FREQ(hi));
+                      smp_processor_id(),
+                      amd_parse_freq(c->x86, val),
+                      amd_parse_freq(c->x86, lo),
+                      amd_parse_freq(c->x86, hi));
        else if (h && !rdmsr_safe(0xC0010064, hi) && (hi >> 63))
                printk("CPU%u: %lu ... %lu MHz\n",
-                      smp_processor_id(), FREQ(lo), FREQ(hi));
+                      smp_processor_id(),
+                      amd_parse_freq(c->x86, lo),
+                      amd_parse_freq(c->x86, hi));
        else
-               printk("CPU%u: %lu MHz\n", smp_processor_id(), FREQ(lo));
-#undef FREQ
+               printk("CPU%u: %lu MHz\n", smp_processor_id(),
+                      amd_parse_freq(c->x86, lo));
 }
 
 void cf_check early_init_amd(struct cpuinfo_x86 *c)
-- 
2.34.1