On Fri, Oct 07, 2022 at 09:34:46AM -0500, Scott Cheloha wrote:
> On Thu, Sep 29, 2022 at 09:14:51AM -0500, Scott Cheloha wrote:
> > This patch computes the TSC frequency for AMD family 17h and 19h CPUs
> > (Zen microarchitecture and up) from AMD-specific MSRs. Computing the
> > TSC frequency is faster than calibrating with a separate timer and
> > introduces no error.
> >
> > We already do this for Intel CPUs in tsc_freq_cpuid().
> >
> > I got several successful test reports on family 17h and 19h CPUs in
> > response to this mail:
> >
> > https://marc.info/?l=openbsd-tech&m=166394236029484&w=2
> >
> > The details for computing the frequency are in the PPR for 17h and
> > 19h, found here (page numbers are cited in the patch):
> >
> > https://www.amd.com/system/files/TechDocs/55570-B1-PUB.zip
> > https://www.amd.com/system/files/TechDocs/56214-B0-PUB.zip
> >
> > The process is slightly more complicated on AMD CPU families 10h-16h.
> > I will deal with them in a separate commit.
> >
> > ok?
>
> 1 week bump.
Whoops, forgot the patch, my mistake.
Index: amd64/tsc.c
===================================================================
RCS file: /cvs/src/sys/arch/amd64/amd64/tsc.c,v
retrieving revision 1.29
diff -u -p -r1.29 tsc.c
--- amd64/tsc.c 22 Sep 2022 04:57:08 -0000 1.29
+++ amd64/tsc.c 29 Sep 2022 01:52:27 -0000
@@ -100,6 +100,66 @@ tsc_freq_cpuid(struct cpu_info *ci)
return (0);
}
+uint64_t
+tsc_freq_msr(struct cpu_info *ci)
+{
+ uint64_t base, def, divisor, multiplier;
+
+ if (strcmp(cpu_vendor, "AuthenticAMD") != 0)
+ return 0;
+
+ /*
+ * All family 10h+ CPUs have MSR_HWCR and the TscFreqSel bit.
+ * If TscFreqSel is not set the TSC does not advance at the P0
+ * frequency, in which case something is wrong and we need to
+ * calibrate by hand.
+ */
+ if (ci->ci_family < 0x10)
+ return 0;
+ if (!ISSET(rdmsr(MSR_HWCR), HWCR_TSCFREQSEL))
+ return 0;
+
+ /*
+ * In family 10h+, core P-state voltage/frequency definitions
+ * are kept in MSR_PSTATEDEF. We're interested in the MSR
+ * describing P0. If the EN bit isn't set, the register doesn't
+ * define a valid P-state.
+ */
+ def = rdmsr(MSR_PSTATEDEF(0));
+ if (!ISSET(def, PSTATEDEF_EN))
+ return 0;
+
+ switch (ci->ci_family) {
+ case 0x17:
+ case 0x19:
+ /*
+ * PPR for AMD Family 17h [...]:
+ * Models 01h,08h B2, Rev 3.03, pp. 33, 139-140
+ * Model 18h B1, Rev 3.16, pp. 36, 143-144
+ * Model 60h A1, Rev 3.06, pp. 33, 155-157
+ * Model 71h B0, Rev 3.06, pp. 28, 150-151
+ *
+ * PPR for AMD Family 19h [...]:
+ * Model 21h B0, Rev 3.05, pp. 33, 166-167
+ *
+ * OSRR for AMD Family 17h processors,
+ * Models 00h-2Fh, Rev 3.03, pp. 130-131
+ */
+ base = 200000000; /* 200.0 MHz */
+ divisor = (def >> 8) & 0x3f;
+ if (divisor < 0x8 || divisor > 0x2c)
+ return 0; /* reserved */
+ if (divisor >= 0x1b && divisor % 2 == 1)
+ return 0; /* reserved */
+ multiplier = def & 0xff;
+ break;
+ default:
+ return 0;
+ }
+
+ return base * multiplier / divisor;
+}
+
void
tsc_identify(struct cpu_info *ci)
{
@@ -118,6 +178,8 @@ tsc_identify(struct cpu_info *ci)
tsc_is_invariant = 1;
tsc_frequency = tsc_freq_cpuid(ci);
+ if (tsc_frequency == 0)
+ tsc_frequency = tsc_freq_msr(ci);
if (tsc_frequency > 0)
delay_init(tsc_delay, 5000);
}
Index: include/specialreg.h
===================================================================
RCS file: /cvs/src/sys/arch/amd64/include/specialreg.h,v
retrieving revision 1.94
diff -u -p -r1.94 specialreg.h
--- include/specialreg.h 30 Aug 2022 17:09:21 -0000 1.94
+++ include/specialreg.h 29 Sep 2022 01:52:28 -0000
@@ -540,6 +540,10 @@
*/
#define MSR_HWCR 0xc0010015
#define HWCR_FFDIS 0x00000040
+#define HWCR_TSCFREQSEL 0x01000000
+
+#define MSR_PSTATEDEF(_n) (0xc0010064 + (_n))
+#define PSTATEDEF_EN 0x8000000000000000ULL
#define MSR_NB_CFG 0xc001001f
#define NB_CFG_DISIOREQLOCK 0x0000000000000004ULL
