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>

src/cpu/intel/fsp_model_406dx/Kconfig

@@ -32,7 +32,6 @@ config CPU_SPECIFIC_OPTIONS
 	select PARALLEL_CPU_INIT
 	select TSC_SYNC_MFENCE
 	select TSC_MONOTONIC_TIMER
-	select TSC_CONSTANT_RATE
 	select CPU_INTEL_COMMON
 	select CPU_INTEL_COMMON_TIMEBASE
 	select NO_SMM

src/cpu/intel/haswell/Kconfig

@@ -14,7 +14,6 @@ config CPU_SPECIFIC_OPTIONS
 	select MMX
 	select SSE2
 	select UDELAY_TSC
-	select TSC_CONSTANT_RATE
 	select TSC_MONOTONIC_TIMER
 	select SUPPORT_CPU_UCODE_IN_CBFS
 	#select AP_IN_SIPI_WAIT

src/cpu/intel/model_1067x/Kconfig

@@ -7,7 +7,6 @@ config CPU_INTEL_MODEL_1067X
 	select SMP
 	select SSE2
 	select UDELAY_TSC
-	select TSC_CONSTANT_RATE
 	select TSC_MONOTONIC_TIMER
 	select TSC_SYNC_MFENCE
 	select SUPPORT_CPU_UCODE_IN_CBFS

src/cpu/intel/model_106cx/Kconfig

@@ -7,7 +7,6 @@ config CPU_INTEL_MODEL_106CX
 	select SMP
 	select SSE2
 	select UDELAY_TSC
-	select TSC_CONSTANT_RATE
 	select TSC_MONOTONIC_TIMER
 	select SIPI_VECTOR_IN_ROM
 	select AP_IN_SIPI_WAIT

src/cpu/intel/model_2065x/Kconfig

@@ -12,7 +12,6 @@ config CPU_SPECIFIC_OPTIONS
 	select SMP
 	select SSE2
 	select UDELAY_TSC
-	select TSC_CONSTANT_RATE
 	select TSC_MONOTONIC_TIMER
 	select SUPPORT_CPU_UCODE_IN_CBFS
 	select PARALLEL_CPU_INIT

src/cpu/intel/model_206ax/Kconfig

@@ -13,7 +13,6 @@ config CPU_SPECIFIC_OPTIONS
 	select MMX
 	select SSE2
 	select UDELAY_TSC
-	select TSC_CONSTANT_RATE
 	select TSC_MONOTONIC_TIMER
 	select SUPPORT_CPU_UCODE_IN_CBFS
 	#select AP_IN_SIPI_WAIT

src/cpu/intel/model_6ex/Kconfig

@@ -7,7 +7,6 @@ config CPU_INTEL_MODEL_6EX
 	select SMP
 	select SSE2
 	select UDELAY_TSC
-	select TSC_CONSTANT_RATE
 	select TSC_MONOTONIC_TIMER
 	select AP_IN_SIPI_WAIT
 	select TSC_SYNC_MFENCE

src/cpu/intel/model_6fx/Kconfig

@@ -7,7 +7,6 @@ config CPU_INTEL_MODEL_6FX
 	select SMP
 	select SSE2
 	select UDELAY_TSC
-	select TSC_CONSTANT_RATE
 	select TSC_MONOTONIC_TIMER
 	select AP_IN_SIPI_WAIT
 	select TSC_SYNC_MFENCE

src/cpu/intel/slot_1/Kconfig

@@ -25,6 +25,7 @@ config SLOT_SPECIFIC_OPTIONS # dummy
 	select CPU_INTEL_MODEL_6XX
 	select NO_SMM
 	select NO_MONOTONIC_TIMER
+	select UNKNOWN_TSC_RATE
 
 config DCACHE_RAM_BASE
 	hex

src/cpu/intel/socket_mPGA604/Kconfig

@@ -9,7 +9,6 @@ config SOCKET_SPECIFIC_OPTIONS # dummy
 	select MMX
 	select SSE
 	select UDELAY_TSC
-	select TSC_CONSTANT_RATE
 	select TSC_MONOTONIC_TIMER
 	select SIPI_VECTOR_IN_ROM
 	select C_ENVIRONMENT_BOOTBLOCK

src/cpu/qemu-x86/Kconfig

@@ -20,5 +20,6 @@ config CPU_QEMU_X86
 	select SMP
 	select UDELAY_TSC
 	select TSC_MONOTONIC_TIMER
+	select UNKNOWN_TSC_RATE
 	select C_ENVIRONMENT_BOOTBLOCK
 	select SMM_ASEG

src/cpu/via/nano/Kconfig

@@ -25,6 +25,7 @@ config CPU_SPECIFIC_OPTIONS
 	select ARCH_RAMSTAGE_X86_32
 	select UDELAY_TSC
 	select TSC_MONOTONIC_TIMER
+	select UNKNOWN_TSC_RATE
 	select MMX
 	select SSE2
 	select SUPPORT_CPU_UCODE_IN_CBFS

src/cpu/x86/Kconfig

@@ -34,12 +34,9 @@ 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 UNKNOWN_TSC_RATE
+	bool
+	default y if LAPIC_MONOTONIC_TIMER
 
 config TSC_MONOTONIC_TIMER
 	def_bool n

src/cpu/x86/tsc/Makefile.inc

@@ -1,6 +1,6 @@
 bootblock-$(CONFIG_UDELAY_TSC) += delay_tsc.c
 ramstage-$(CONFIG_UDELAY_TSC) += delay_tsc.c
-romstage-$(CONFIG_TSC_CONSTANT_RATE) += delay_tsc.c
-verstage-$(CONFIG_TSC_CONSTANT_RATE) += delay_tsc.c
-postcar-$(CONFIG_TSC_CONSTANT_RATE) += delay_tsc.c
-smm-$(CONFIG_TSC_CONSTANT_RATE) += delay_tsc.c
+romstage-$(CONFIG_UDELAY_TSC) += delay_tsc.c
+verstage-$(CONFIG_UDELAY_TSC) += delay_tsc.c
+postcar-$(CONFIG_UDELAY_TSC) += delay_tsc.c
+smm-$(CONFIG_UDELAY_TSC) += delay_tsc.c

src/cpu/x86/tsc/delay_tsc.c

@@ -18,26 +18,9 @@
 #include <delay.h>
 #include <thread.h>
 
-static unsigned long clocks_per_usec CAR_GLOBAL;
-
-static unsigned long calibrate_tsc(void)
-{
-	if (CONFIG(TSC_CONSTANT_RATE))
-		return tsc_freq_mhz();
-	else
-		return calibrate_tsc_with_pit();
-}
-
 void init_timer(void)
 {
-	if (!car_get_var(clocks_per_usec))
-		car_set_var(clocks_per_usec, calibrate_tsc());
-}
-
-static inline unsigned long get_clocks_per_usec(void)
-{
-	init_timer();
-	return car_get_var(clocks_per_usec);
+	(void)tsc_freq_mhz();
 }
 
 void udelay(unsigned int us)
@@ -51,7 +34,7 @@ void udelay(unsigned int us)
 
 	start = rdtscll();
 	clocks = us;
-	clocks *= get_clocks_per_usec();
+	clocks *= tsc_freq_mhz();
 	current = rdtscll();
 	while ((current - start) < clocks) {
 		cpu_relax();
@@ -89,7 +72,7 @@ void timer_monotonic_get(struct mono_time *mt)
 
 	current_tick = rdtscll();
 	ticks_elapsed = current_tick - mono_counter->last_value;
-	ticks_per_usec = get_clocks_per_usec();
+	ticks_per_usec = tsc_freq_mhz();
 
 	/* Update current time and tick values only if a full tick occurred. */
 	if (ticks_elapsed >= ticks_per_usec) {