timestamp: add tick frequency to exported table

Add the timestamp tick frequency within the timestamp table so
the cbmem utility doesn't try to figure it out on its own. Those
paths still exist for x86 systems which don't provide tsc_freq_mhz().
All other non-x86 systems use the monotonic timer which has a 1us
granularity or 1MHz.

One of the main reasons is that Linux is reporting
/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq as the true
turbo frequency on turbo enables machines. This change also fixes
the p-state values honored in cpufreq for turbo machines in that
turbo p-pstates were reported as 100MHz greater than nominal.

BUG=chrome-os-partner:44669
BRANCH=firmware-strago-7287.B
TEST=Built and booted on glados. Confirmed table frequency honored.

Change-Id: I763fe2d9a7b01d0ef5556e5abff36032062f5801
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/11470
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/src/arch/x86/timestamp.c b/src/arch/x86/timestamp.c
index 9df505a570..d308146070 100644
--- a/src/arch/x86/timestamp.c
+++ b/src/arch/x86/timestamp.c
@@ -24,3 +24,16 @@ uint64_t timestamp_get(void)
 {
 	return rdtscll();
 }
+
+unsigned long __attribute__((weak)) tsc_freq_mhz(void)
+{
+	/* Default to not knowing TSC frequency. cbmem will have to fallback
+	 * on trying to determine it in userspace. */
+	return 0;
+}
+
+int timestamp_tick_freq_mhz(void)
+{
+	/* Chipsets that have a constant TSC provide this value correctly. */
+	return tsc_freq_mhz();
+}