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| author | Kyösti Mälkki <kyosti.malkki@gmail.com> | 2019-10-31 14:52:20 +0200 |
|---|---|---|
| committer | Kyösti Mälkki <kyosti.malkki@gmail.com> | 2019-11-03 06:15:35 +0000 |
| commit | 0d6ddf8da7632e775dde92c9114ac6ace5ca5f14 (patch) | |
| tree | 67b37afc2c6bc3cfaa3750a87394c5b056067137 /src/drivers | |
| parent | ea2bec2c4b1a986b059147506c99a202d5c8fad3 (diff) | |
cpu/x86/tsc: Flip and rename TSC_CONSTANT_RATE to UNKNOWN_TSC_RATE
The x86 timers are a bit of a mess. Cases where different stages use
different counters and timestamps use different counters from udelays.
The original intention was to only flip TSC_CONSTANT_RATE Kconfig
to NOT_CONSTANT_TSC_RATE. The name would be incorrect though, those
counters do run with a constant rate but we just lack tsc_freq_mhz()
implementation for three platforms.
Note that for boards with UNKNOWN_TSC_RATE=y, each stage will have a
slow run of calibrate_tsc_with_pit(). This is easy enough to fix with
followup implementation of tsc_freq_mhz() for the platforms.
Implementations with LAPIC_MONOTONIC_TIMER typically will not have
tsc_freq_mhz() implemented and default to UNKNOWN_TSC_RATE. However,
as they don't use TSC for udelay() the slow calibrate_tsc_with_pit()
is avoided.
Because x86/tsc_delay.tsc was using two different guards and nb/via/vx900
claimed UDELAY_TSC, but pulled UDELAY_IO implementation, we also switch
that romstage to use UDELAY_TSC.
Change-Id: I1690cb80295d6b006b75ed69edea28899b674b68
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33928
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Diffstat (limited to 'src/drivers')
| -rw-r--r-- | src/drivers/pc80/pc/i8254.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/src/drivers/pc80/pc/i8254.c b/src/drivers/pc80/pc/i8254.c index 8e15d4ded1..654f84a6d7 100644 --- a/src/drivers/pc80/pc/i8254.c +++ b/src/drivers/pc80/pc/i8254.c @@ -11,6 +11,7 @@ * GNU General Public License for more details. */ +#include <arch/early_variables.h> #include <arch/io.h> #include <commonlib/helpers.h> #include <cpu/x86/tsc.h> @@ -122,3 +123,25 @@ unsigned long calibrate_tsc_with_pit(void) bad_ctc: return 0; } + +#if CONFIG(UNKNOWN_TSC_RATE) +static u32 g_timer_tsc CAR_GLOBAL; + +unsigned long tsc_freq_mhz(void) +{ + u32 tsc; + + tsc = car_get_var(g_timer_tsc); + if (tsc > 0) + return tsc; + + tsc = calibrate_tsc_with_pit(); + + /* Set some semi-ridiculous rate if approximation fails. */ + if (tsc == 0) + tsc = 5000; + + car_set_var(g_timer_tsc, tsc); + return tsc; +} +#endif |