/*
* Copyright (c) 2012 The Chromium OS Authors.
*
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License as
- * published by the Free Software Foundation; either version 2 of
- * the License, or (at your option) any later version.
+ * TSC calibration codes are adapted from Linux kernel
+ * arch/x86/kernel/tsc_msr.c and arch/x86/kernel/tsc.c
*
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
- * MA 02111-1307 USA
+ * SPDX-License-Identifier: GPL-2.0+
*/
#include <common.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;
* restart. This yields a free running counter guaranteed to take almost 6
* years to wrap around even at 100GHz clock rate.
*/
-u64 get_ticks(void)
+u64 __attribute__((no_instrument_function)) get_ticks(void)
{
u64 now_tick = rdtsc();
return now_tick - gd->arch.tsc_base;
}
-#define PLATFORM_INFO_MSR 0xce
-
/* Get the speed of the TSC timer in MHz */
-unsigned long get_tbclk_mhz(void)
+unsigned __attribute__((no_instrument_function)) long get_tbclk_mhz(void)
{
- u32 ratio;
- u64 platform_info = native_read_msr(PLATFORM_INFO_MSR);
+ unsigned long fast_calibrate;
- /* 100MHz times Max Non Turbo ratio */
- ratio = (platform_info >> 8) & 0xff;
- return 100 * ratio;
+ 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_ms_timer() - base;
}
-ulong timer_get_us(void)
+ulong __attribute__((no_instrument_function)) timer_get_us(void)
{
return get_ticks() / get_tbclk_mhz();
}
stop = now + usec * get_tbclk_mhz();
while ((int64_t)(stop - get_ticks()) > 0)
+#if defined(CONFIG_QEMU) && defined(CONFIG_SMP)
+ /*
+ * Add a 'pause' instruction on qemu target,
+ * to give other VCPUs a chance to run.
+ */
+ asm volatile("pause");
+#else
;
+#endif
}
int timer_init(void)
{
- /* Nothing to do here - the timer needs no init */
+#ifdef CONFIG_SYS_PCAT_TIMER
+ /* Set up the PCAT timer if required */
+ pcat_timer_init();
+#endif
+
return 0;
}
projects / u-boot / blobdiff