Aaron Durbin (adurbin@google.com) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/3168
-gerrit
commit a5a317bd47de7ce5c0dbba3df0c874cca819f2c1 Author: Aaron Durbin adurbin@chromium.org Date: Wed May 1 15:27:09 2013 -0500
x86: add TSC_CONSTANT_RATE option
Some boards use the local apic for udelay(), but they also provide their own implementation of udelay() for SMM. The reason for using the local apic for udelay() in ramstage is to not have to pay the penalty of calibrating the TSC frequency. Therefore provide a TSC_CONSTANT_RATE option to indicate that TSC calibration is not needed. Instead rely on the presence of a tsc_freq_mhz() function provided by the cpu/board. Additionally, assume that if TSC_CONSTANT_RATE is selected the udelay() function in SMM will be the tsc.
Change-Id: I1629c2fbe3431772b4e80495160584fb6f599e9e Signed-off-by: Aaron Durbin adurbin@chromium.org --- src/cpu/x86/Kconfig | 7 +++++++ src/cpu/x86/tsc/Makefile.inc | 4 ++++ src/cpu/x86/tsc/delay_tsc.c | 27 ++++++++++++++++++++++++--- src/include/cpu/x86/tsc.h | 4 ++++ 4 files changed, 39 insertions(+), 3 deletions(-)
diff --git a/src/cpu/x86/Kconfig b/src/cpu/x86/Kconfig index 5cf40fa..c64a8e4 100644 --- a/src/cpu/x86/Kconfig +++ b/src/cpu/x86/Kconfig @@ -25,6 +25,13 @@ config UDELAY_TSC bool default n
+config TSC_CONSTANT_RATE + def_bool n + depends on UDELAY_TSC + help + This option asserts that the TSC ticks at a known constant rate. + Therefore, no TSC calibration is required. + config TSC_MONOTONIC_TIMER def_bool n depends on UDELAY_TSC diff --git a/src/cpu/x86/tsc/Makefile.inc b/src/cpu/x86/tsc/Makefile.inc index 44bfe85..3bbae84 100644 --- a/src/cpu/x86/tsc/Makefile.inc +++ b/src/cpu/x86/tsc/Makefile.inc @@ -1,2 +1,6 @@ ramstage-$(CONFIG_UDELAY_TSC) += delay_tsc.c +romstage-$(CONFIG_TSC_CONSTANT_RATE) += delay_tsc.c +ifeq ($(CONFIG_HAVE_SMI_HANDLER),y) +smm-$(CONFIG_TSC_CONSTANT_RATE) += delay_tsc.c +endif
diff --git a/src/cpu/x86/tsc/delay_tsc.c b/src/cpu/x86/tsc/delay_tsc.c index e4993d0..0540496 100644 --- a/src/cpu/x86/tsc/delay_tsc.c +++ b/src/cpu/x86/tsc/delay_tsc.c @@ -5,8 +5,16 @@ #include <smp/spinlock.h> #include <delay.h>
+#if !defined(__PRE_RAM__) + static unsigned long clocks_per_usec;
+#if CONFIG_TSC_CONSTANT_RATE +static unsigned long calibrate_tsc(void) +{ + return tsc_freq_mhz(); +} +#else /* CONFIG_TSC_CONSTANT_RATE */ #if !CONFIG_TSC_CALIBRATE_WITH_IO #define CLOCK_TICK_RATE 1193180U /* Underlying HZ */
@@ -139,6 +147,7 @@ static unsigned long long calibrate_tsc(void)
#endif /* CONFIG_TSC_CALIBRATE_WITH_IO */ +#endif /* CONFIG_TSC_CONSTANT_RATE */
void init_timer(void) { @@ -148,15 +157,27 @@ void init_timer(void) } }
+static inline unsigned long get_clocks_per_usec(void) +{ + init_timer(); + return clocks_per_usec; +} +#else /* !defined(__PRE_RAM__) */ +/* romstage calls into cpu/board specific function every time. */ +static inline unsigned long get_clocks_per_usec(void) +{ + return tsc_freq_mhz(); +} +#endif /* !defined(__PRE_RAM__) */ + void udelay(unsigned us) { unsigned long long count; unsigned long long stop; unsigned long long clocks;
- init_timer(); clocks = us; - clocks *= clocks_per_usec; + clocks *= get_clocks_per_usec(); count = rdtscll(); stop = clocks + count; while(stop > count) { @@ -165,7 +186,7 @@ void udelay(unsigned us) } }
-#if CONFIG_TSC_MONOTONIC_TIMER +#if CONFIG_TSC_MONOTONIC_TIMER && !defined(__PRE_RAM__) && !defined(__SMM__) #include <timer.h>
static struct monotonic_counter { diff --git a/src/include/cpu/x86/tsc.h b/src/include/cpu/x86/tsc.h index 6ce7f5f..8e49a66 100644 --- a/src/include/cpu/x86/tsc.h +++ b/src/include/cpu/x86/tsc.h @@ -40,4 +40,8 @@ static inline unsigned long long rdtscll(void) } #endif
+#if CONFIG_TSC_CONSTANT_RATE +unsigned long tsc_freq_mhz(void); +#endif + #endif /* CPU_X86_TSC_H */