u-boot/arch/x86/lib/tsc_timer.c
Bin Meng 3ba6a0f4f6 x86: Allow a hardcoded TSC frequency provided by Kconfig
By default U-Boot automatically calibrates TSC running frequency via
MSR and PIT. The calibration may not work on every x86 processor, so
a new Kconfig option CONFIG_TSC_CALIBRATION_BYPASS is introduced to
allow bypassing the calibration and assign a hardcoded TSC frequency
CONFIG_TSC_FREQ_IN_MHZ.

Normally the bypass should be turned on in a simulation environment
like qemu.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
2015-01-13 07:25:02 -08:00

369 lines
9 KiB
C

/*
* Copyright (c) 2012 The Chromium OS Authors.
*
* TSC calibration codes are adapted from Linux kernel
* arch/x86/kernel/tsc_msr.c and arch/x86/kernel/tsc.c
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include <common.h>
#include <malloc.h>
#include <asm/io.h>
#include <asm/i8254.h>
#include <asm/ibmpc.h>
#include <asm/msr.h>
#include <asm/u-boot-x86.h>
/* CPU reference clock frequency: in KHz */
#define FREQ_83 83200
#define FREQ_100 99840
#define FREQ_133 133200
#define FREQ_166 166400
#define MAX_NUM_FREQS 8
DECLARE_GLOBAL_DATA_PTR;
/*
* According to Intel 64 and IA-32 System Programming Guide,
* if MSR_PERF_STAT[31] is set, the maximum resolved bus ratio can be
* read in MSR_PLATFORM_ID[12:8], otherwise in MSR_PERF_STAT[44:40].
* Unfortunately some Intel Atom SoCs aren't quite compliant to this,
* so we need manually differentiate SoC families. This is what the
* field msr_plat does.
*/
struct freq_desc {
u8 x86_family; /* CPU family */
u8 x86_model; /* model */
/* 2: use 100MHz, 1: use MSR_PLATFORM_INFO, 0: MSR_IA32_PERF_STATUS */
u8 msr_plat;
u32 freqs[MAX_NUM_FREQS];
};
static struct freq_desc freq_desc_tables[] = {
/* PNW */
{ 6, 0x27, 0, { 0, 0, 0, 0, 0, FREQ_100, 0, FREQ_83 } },
/* CLV+ */
{ 6, 0x35, 0, { 0, FREQ_133, 0, 0, 0, FREQ_100, 0, FREQ_83 } },
/* TNG */
{ 6, 0x4a, 1, { 0, FREQ_100, FREQ_133, 0, 0, 0, 0, 0 } },
/* VLV2 */
{ 6, 0x37, 1, { FREQ_83, FREQ_100, FREQ_133, FREQ_166, 0, 0, 0, 0 } },
/* Ivybridge */
{ 6, 0x3a, 2, { 0, 0, 0, 0, 0, 0, 0, 0 } },
/* ANN */
{ 6, 0x5a, 1, { FREQ_83, FREQ_100, FREQ_133, FREQ_100, 0, 0, 0, 0 } },
};
static int match_cpu(u8 family, u8 model)
{
int i;
for (i = 0; i < ARRAY_SIZE(freq_desc_tables); i++) {
if ((family == freq_desc_tables[i].x86_family) &&
(model == freq_desc_tables[i].x86_model))
return i;
}
return -1;
}
/* Map CPU reference clock freq ID(0-7) to CPU reference clock freq(KHz) */
#define id_to_freq(cpu_index, freq_id) \
(freq_desc_tables[cpu_index].freqs[freq_id])
/*
* Do MSR calibration only for known/supported CPUs.
*
* Returns the calibration value or 0 if MSR calibration failed.
*/
static unsigned long __maybe_unused try_msr_calibrate_tsc(void)
{
u32 lo, hi, ratio, freq_id, freq;
unsigned long res;
int cpu_index;
cpu_index = match_cpu(gd->arch.x86, gd->arch.x86_model);
if (cpu_index < 0)
return 0;
if (freq_desc_tables[cpu_index].msr_plat) {
rdmsr(MSR_PLATFORM_INFO, lo, hi);
ratio = (lo >> 8) & 0x1f;
} else {
rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
ratio = (hi >> 8) & 0x1f;
}
debug("Maximum core-clock to bus-clock ratio: 0x%x\n", ratio);
if (!ratio)
goto fail;
if (freq_desc_tables[cpu_index].msr_plat == 2) {
/* TODO: Figure out how best to deal with this */
freq = FREQ_100;
debug("Using frequency: %u KHz\n", freq);
} else {
/* Get FSB FREQ ID */
rdmsr(MSR_FSB_FREQ, lo, hi);
freq_id = lo & 0x7;
freq = id_to_freq(cpu_index, freq_id);
debug("Resolved frequency ID: %u, frequency: %u KHz\n",
freq_id, freq);
}
if (!freq)
goto fail;
/* TSC frequency = maximum resolved freq * maximum resolved bus ratio */
res = freq * ratio / 1000;
debug("TSC runs at %lu MHz\n", res);
return res;
fail:
debug("Fast TSC calibration using MSR failed\n");
return 0;
}
/*
* This reads the current MSB of the PIT counter, and
* checks if we are running on sufficiently fast and
* non-virtualized hardware.
*
* Our expectations are:
*
* - the PIT is running at roughly 1.19MHz
*
* - each IO is going to take about 1us on real hardware,
* but we allow it to be much faster (by a factor of 10) or
* _slightly_ slower (ie we allow up to a 2us read+counter
* update - anything else implies a unacceptably slow CPU
* or PIT for the fast calibration to work.
*
* - with 256 PIT ticks to read the value, we have 214us to
* see the same MSB (and overhead like doing a single TSC
* read per MSB value etc).
*
* - We're doing 2 reads per loop (LSB, MSB), and we expect
* them each to take about a microsecond on real hardware.
* So we expect a count value of around 100. But we'll be
* generous, and accept anything over 50.
*
* - if the PIT is stuck, and we see *many* more reads, we
* return early (and the next caller of pit_expect_msb()
* then consider it a failure when they don't see the
* next expected value).
*
* These expectations mean that we know that we have seen the
* transition from one expected value to another with a fairly
* high accuracy, and we didn't miss any events. We can thus
* use the TSC value at the transitions to calculate a pretty
* good value for the TSC frequencty.
*/
static inline int pit_verify_msb(unsigned char val)
{
/* Ignore LSB */
inb(0x42);
return inb(0x42) == val;
}
static inline int pit_expect_msb(unsigned char val, u64 *tscp,
unsigned long *deltap)
{
int count;
u64 tsc = 0, prev_tsc = 0;
for (count = 0; count < 50000; count++) {
if (!pit_verify_msb(val))
break;
prev_tsc = tsc;
tsc = rdtsc();
}
*deltap = rdtsc() - prev_tsc;
*tscp = tsc;
/*
* We require _some_ success, but the quality control
* will be based on the error terms on the TSC values.
*/
return count > 5;
}
/*
* How many MSB values do we want to see? We aim for
* a maximum error rate of 500ppm (in practice the
* real error is much smaller), but refuse to spend
* more than 50ms on it.
*/
#define MAX_QUICK_PIT_MS 50
#define MAX_QUICK_PIT_ITERATIONS (MAX_QUICK_PIT_MS * PIT_TICK_RATE / 1000 / 256)
static unsigned long __maybe_unused quick_pit_calibrate(void)
{
int i;
u64 tsc, delta;
unsigned long d1, d2;
/* Set the Gate high, disable speaker */
outb((inb(0x61) & ~0x02) | 0x01, 0x61);
/*
* Counter 2, mode 0 (one-shot), binary count
*
* NOTE! Mode 2 decrements by two (and then the
* output is flipped each time, giving the same
* final output frequency as a decrement-by-one),
* so mode 0 is much better when looking at the
* individual counts.
*/
outb(0xb0, 0x43);
/* Start at 0xffff */
outb(0xff, 0x42);
outb(0xff, 0x42);
/*
* The PIT starts counting at the next edge, so we
* need to delay for a microsecond. The easiest way
* to do that is to just read back the 16-bit counter
* once from the PIT.
*/
pit_verify_msb(0);
if (pit_expect_msb(0xff, &tsc, &d1)) {
for (i = 1; i <= MAX_QUICK_PIT_ITERATIONS; i++) {
if (!pit_expect_msb(0xff-i, &delta, &d2))
break;
/*
* Iterate until the error is less than 500 ppm
*/
delta -= tsc;
if (d1+d2 >= delta >> 11)
continue;
/*
* Check the PIT one more time to verify that
* all TSC reads were stable wrt the PIT.
*
* This also guarantees serialization of the
* last cycle read ('d2') in pit_expect_msb.
*/
if (!pit_verify_msb(0xfe - i))
break;
goto success;
}
}
debug("Fast TSC calibration failed\n");
return 0;
success:
/*
* Ok, if we get here, then we've seen the
* MSB of the PIT decrement 'i' times, and the
* error has shrunk to less than 500 ppm.
*
* As a result, we can depend on there not being
* any odd delays anywhere, and the TSC reads are
* reliable (within the error).
*
* kHz = ticks / time-in-seconds / 1000;
* kHz = (t2 - t1) / (I * 256 / PIT_TICK_RATE) / 1000
* kHz = ((t2 - t1) * PIT_TICK_RATE) / (I * 256 * 1000)
*/
delta *= PIT_TICK_RATE;
delta /= (i*256*1000);
debug("Fast TSC calibration using PIT\n");
return delta / 1000;
}
void timer_set_base(u64 base)
{
gd->arch.tsc_base = base;
}
/*
* Get the number of CPU time counter ticks since it was read first time after
* restart. This yields a free running counter guaranteed to take almost 6
* years to wrap around even at 100GHz clock rate.
*/
u64 __attribute__((no_instrument_function)) get_ticks(void)
{
u64 now_tick = rdtsc();
/* We assume that 0 means the base hasn't been set yet */
if (!gd->arch.tsc_base)
panic("No tick base available");
return now_tick - gd->arch.tsc_base;
}
/* Get the speed of the TSC timer in MHz */
unsigned __attribute__((no_instrument_function)) long get_tbclk_mhz(void)
{
unsigned long fast_calibrate;
if (gd->arch.tsc_mhz)
return gd->arch.tsc_mhz;
#ifdef CONFIG_TSC_CALIBRATION_BYPASS
fast_calibrate = CONFIG_TSC_FREQ_IN_MHZ;
#else
fast_calibrate = try_msr_calibrate_tsc();
if (!fast_calibrate) {
fast_calibrate = quick_pit_calibrate();
if (!fast_calibrate)
panic("TSC frequency is ZERO");
}
#endif
gd->arch.tsc_mhz = fast_calibrate;
return fast_calibrate;
}
unsigned long get_tbclk(void)
{
return get_tbclk_mhz() * 1000 * 1000;
}
static ulong get_ms_timer(void)
{
return (get_ticks() * 1000) / get_tbclk();
}
ulong get_timer(ulong base)
{
return get_ms_timer() - base;
}
ulong __attribute__((no_instrument_function)) timer_get_us(void)
{
return get_ticks() / get_tbclk_mhz();
}
ulong timer_get_boot_us(void)
{
return timer_get_us();
}
void __udelay(unsigned long usec)
{
u64 now = get_ticks();
u64 stop;
stop = now + usec * get_tbclk_mhz();
while ((int64_t)(stop - get_ticks()) > 0)
;
}
int timer_init(void)
{
#ifdef CONFIG_SYS_PCAT_TIMER
/* Set up the PCAT timer if required */
pcat_timer_init();
#endif
return 0;
}