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https://github.com/brain-hackers/u-boot-brain
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![Bin Meng](/assets/img/avatar_default.png)
At present if TSC frequency is provided in the device tree, it takes precedence over hardware calibration result. This swaps the order to try hardware calibration first and uses device tree as last resort. This can be helpful when a generic dts (eg: coreboot/efi payload) is supposed to work on as many hardware as possible, including emulators like QEMU where TSC hardware calibration sometimes fails. Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
429 lines
10 KiB
C
429 lines
10 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* Copyright (c) 2012 The Chromium OS Authors.
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*
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* TSC calibration codes are adapted from Linux kernel
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* arch/x86/kernel/tsc_msr.c and arch/x86/kernel/tsc.c
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*/
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#include <common.h>
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#include <dm.h>
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#include <malloc.h>
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#include <timer.h>
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#include <asm/cpu.h>
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#include <asm/io.h>
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#include <asm/i8254.h>
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#include <asm/ibmpc.h>
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#include <asm/msr.h>
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#include <asm/u-boot-x86.h>
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#define MAX_NUM_FREQS 9
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DECLARE_GLOBAL_DATA_PTR;
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static unsigned long cpu_mhz_from_cpuid(void)
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{
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if (gd->arch.x86_vendor != X86_VENDOR_INTEL)
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return 0;
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if (cpuid_eax(0) < 0x16)
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return 0;
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return cpuid_eax(0x16);
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}
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/*
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* According to Intel 64 and IA-32 System Programming Guide,
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* if MSR_PERF_STAT[31] is set, the maximum resolved bus ratio can be
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* read in MSR_PLATFORM_ID[12:8], otherwise in MSR_PERF_STAT[44:40].
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* Unfortunately some Intel Atom SoCs aren't quite compliant to this,
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* so we need manually differentiate SoC families. This is what the
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* field msr_plat does.
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*/
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struct freq_desc {
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u8 x86_family; /* CPU family */
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u8 x86_model; /* model */
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/* 2: use 100MHz, 1: use MSR_PLATFORM_INFO, 0: MSR_IA32_PERF_STATUS */
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u8 msr_plat;
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u32 freqs[MAX_NUM_FREQS];
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};
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static struct freq_desc freq_desc_tables[] = {
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/* PNW */
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{ 6, 0x27, 0, { 0, 0, 0, 0, 0, 99840, 0, 83200, 0 } },
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/* CLV+ */
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{ 6, 0x35, 0, { 0, 133200, 0, 0, 0, 99840, 0, 83200, 0 } },
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/* TNG - Intel Atom processor Z3400 series */
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{ 6, 0x4a, 1, { 0, 100000, 133300, 0, 0, 0, 0, 0, 0 } },
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/* VLV2 - Intel Atom processor E3000, Z3600, Z3700 series */
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{ 6, 0x37, 1, { 83300, 100000, 133300, 116700, 80000, 0, 0, 0, 0 } },
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/* ANN - Intel Atom processor Z3500 series */
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{ 6, 0x5a, 1, { 83300, 100000, 133300, 100000, 0, 0, 0, 0, 0 } },
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/* AMT - Intel Atom processor X7-Z8000 and X5-Z8000 series */
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{ 6, 0x4c, 1, { 83300, 100000, 133300, 116700,
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80000, 93300, 90000, 88900, 87500 } },
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/* Ivybridge */
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{ 6, 0x3a, 2, { 0, 0, 0, 0, 0, 0, 0, 0, 0 } },
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};
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static int match_cpu(u8 family, u8 model)
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{
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int i;
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for (i = 0; i < ARRAY_SIZE(freq_desc_tables); i++) {
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if ((family == freq_desc_tables[i].x86_family) &&
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(model == freq_desc_tables[i].x86_model))
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return i;
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}
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return -1;
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}
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/* Map CPU reference clock freq ID(0-7) to CPU reference clock freq(KHz) */
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#define id_to_freq(cpu_index, freq_id) \
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(freq_desc_tables[cpu_index].freqs[freq_id])
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/*
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* TSC on Intel Atom SoCs capable of determining TSC frequency by MSR is
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* reliable and the frequency is known (provided by HW).
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*
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* On these platforms PIT/HPET is generally not available so calibration won't
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* work at all and there is no other clocksource to act as a watchdog for the
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* TSC, so we have no other choice than to trust it.
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*
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* Returns the TSC frequency in MHz or 0 if HW does not provide it.
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*/
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static unsigned long __maybe_unused cpu_mhz_from_msr(void)
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{
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u32 lo, hi, ratio, freq_id, freq;
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unsigned long res;
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int cpu_index;
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if (gd->arch.x86_vendor != X86_VENDOR_INTEL)
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return 0;
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cpu_index = match_cpu(gd->arch.x86, gd->arch.x86_model);
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if (cpu_index < 0)
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return 0;
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if (freq_desc_tables[cpu_index].msr_plat) {
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rdmsr(MSR_PLATFORM_INFO, lo, hi);
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ratio = (lo >> 8) & 0xff;
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} else {
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rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
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ratio = (hi >> 8) & 0x1f;
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}
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debug("Maximum core-clock to bus-clock ratio: 0x%x\n", ratio);
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if (freq_desc_tables[cpu_index].msr_plat == 2) {
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/* TODO: Figure out how best to deal with this */
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freq = 100000;
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debug("Using frequency: %u KHz\n", freq);
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} else {
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/* Get FSB FREQ ID */
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rdmsr(MSR_FSB_FREQ, lo, hi);
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freq_id = lo & 0x7;
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freq = id_to_freq(cpu_index, freq_id);
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debug("Resolved frequency ID: %u, frequency: %u KHz\n",
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freq_id, freq);
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}
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/* TSC frequency = maximum resolved freq * maximum resolved bus ratio */
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res = freq * ratio / 1000;
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debug("TSC runs at %lu MHz\n", res);
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return res;
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}
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/*
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* This reads the current MSB of the PIT counter, and
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* checks if we are running on sufficiently fast and
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* non-virtualized hardware.
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*
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* Our expectations are:
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*
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* - the PIT is running at roughly 1.19MHz
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*
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* - each IO is going to take about 1us on real hardware,
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* but we allow it to be much faster (by a factor of 10) or
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* _slightly_ slower (ie we allow up to a 2us read+counter
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* update - anything else implies a unacceptably slow CPU
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* or PIT for the fast calibration to work.
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*
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* - with 256 PIT ticks to read the value, we have 214us to
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* see the same MSB (and overhead like doing a single TSC
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* read per MSB value etc).
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*
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* - We're doing 2 reads per loop (LSB, MSB), and we expect
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* them each to take about a microsecond on real hardware.
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* So we expect a count value of around 100. But we'll be
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* generous, and accept anything over 50.
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*
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* - if the PIT is stuck, and we see *many* more reads, we
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* return early (and the next caller of pit_expect_msb()
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* then consider it a failure when they don't see the
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* next expected value).
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*
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* These expectations mean that we know that we have seen the
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* transition from one expected value to another with a fairly
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* high accuracy, and we didn't miss any events. We can thus
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* use the TSC value at the transitions to calculate a pretty
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* good value for the TSC frequencty.
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*/
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static inline int pit_verify_msb(unsigned char val)
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{
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/* Ignore LSB */
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inb(0x42);
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return inb(0x42) == val;
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}
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static inline int pit_expect_msb(unsigned char val, u64 *tscp,
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unsigned long *deltap)
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{
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int count;
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u64 tsc = 0, prev_tsc = 0;
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for (count = 0; count < 50000; count++) {
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if (!pit_verify_msb(val))
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break;
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prev_tsc = tsc;
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tsc = rdtsc();
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}
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*deltap = rdtsc() - prev_tsc;
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*tscp = tsc;
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/*
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* We require _some_ success, but the quality control
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* will be based on the error terms on the TSC values.
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*/
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return count > 5;
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}
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/*
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* How many MSB values do we want to see? We aim for
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* a maximum error rate of 500ppm (in practice the
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* real error is much smaller), but refuse to spend
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* more than 50ms on it.
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*/
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#define MAX_QUICK_PIT_MS 50
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#define MAX_QUICK_PIT_ITERATIONS (MAX_QUICK_PIT_MS * PIT_TICK_RATE / 1000 / 256)
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static unsigned long __maybe_unused quick_pit_calibrate(void)
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{
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int i;
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u64 tsc, delta;
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unsigned long d1, d2;
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/* Set the Gate high, disable speaker */
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outb((inb(0x61) & ~0x02) | 0x01, 0x61);
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/*
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* Counter 2, mode 0 (one-shot), binary count
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*
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* NOTE! Mode 2 decrements by two (and then the
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* output is flipped each time, giving the same
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* final output frequency as a decrement-by-one),
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* so mode 0 is much better when looking at the
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* individual counts.
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*/
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outb(0xb0, 0x43);
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/* Start at 0xffff */
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outb(0xff, 0x42);
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outb(0xff, 0x42);
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/*
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* The PIT starts counting at the next edge, so we
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* need to delay for a microsecond. The easiest way
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* to do that is to just read back the 16-bit counter
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* once from the PIT.
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*/
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pit_verify_msb(0);
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if (pit_expect_msb(0xff, &tsc, &d1)) {
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for (i = 1; i <= MAX_QUICK_PIT_ITERATIONS; i++) {
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if (!pit_expect_msb(0xff-i, &delta, &d2))
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break;
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/*
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* Iterate until the error is less than 500 ppm
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*/
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delta -= tsc;
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if (d1+d2 >= delta >> 11)
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continue;
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/*
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* Check the PIT one more time to verify that
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* all TSC reads were stable wrt the PIT.
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*
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* This also guarantees serialization of the
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* last cycle read ('d2') in pit_expect_msb.
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*/
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if (!pit_verify_msb(0xfe - i))
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break;
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goto success;
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}
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}
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debug("Fast TSC calibration failed\n");
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return 0;
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success:
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/*
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* Ok, if we get here, then we've seen the
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* MSB of the PIT decrement 'i' times, and the
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* error has shrunk to less than 500 ppm.
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*
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* As a result, we can depend on there not being
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* any odd delays anywhere, and the TSC reads are
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* reliable (within the error).
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*
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* kHz = ticks / time-in-seconds / 1000;
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* kHz = (t2 - t1) / (I * 256 / PIT_TICK_RATE) / 1000
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* kHz = ((t2 - t1) * PIT_TICK_RATE) / (I * 256 * 1000)
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*/
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delta *= PIT_TICK_RATE;
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delta /= (i*256*1000);
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debug("Fast TSC calibration using PIT\n");
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return delta / 1000;
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}
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/* Get the speed of the TSC timer in MHz */
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unsigned notrace long get_tbclk_mhz(void)
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{
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return get_tbclk() / 1000000;
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}
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static ulong get_ms_timer(void)
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{
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return (get_ticks() * 1000) / get_tbclk();
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}
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ulong get_timer(ulong base)
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{
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return get_ms_timer() - base;
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}
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ulong notrace timer_get_us(void)
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{
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return get_ticks() / get_tbclk_mhz();
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}
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ulong timer_get_boot_us(void)
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{
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return timer_get_us();
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}
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void __udelay(unsigned long usec)
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{
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u64 now = get_ticks();
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u64 stop;
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stop = now + usec * get_tbclk_mhz();
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while ((int64_t)(stop - get_ticks()) > 0)
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#if defined(CONFIG_QEMU) && defined(CONFIG_SMP)
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/*
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* Add a 'pause' instruction on qemu target,
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* to give other VCPUs a chance to run.
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*/
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asm volatile("pause");
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#else
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;
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#endif
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}
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static int tsc_timer_get_count(struct udevice *dev, u64 *count)
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{
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u64 now_tick = rdtsc();
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*count = now_tick - gd->arch.tsc_base;
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return 0;
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}
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static void tsc_timer_ensure_setup(bool stop)
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{
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if (gd->arch.tsc_base)
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return;
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gd->arch.tsc_base = rdtsc();
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if (!gd->arch.clock_rate) {
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unsigned long fast_calibrate;
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fast_calibrate = cpu_mhz_from_cpuid();
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if (fast_calibrate)
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goto done;
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fast_calibrate = cpu_mhz_from_msr();
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if (fast_calibrate)
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goto done;
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fast_calibrate = quick_pit_calibrate();
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if (fast_calibrate)
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goto done;
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if (stop)
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panic("TSC frequency is ZERO");
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else
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return;
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done:
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gd->arch.clock_rate = fast_calibrate * 1000000;
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}
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}
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static int tsc_timer_probe(struct udevice *dev)
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{
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struct timer_dev_priv *uc_priv = dev_get_uclass_priv(dev);
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/* Try hardware calibration first */
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tsc_timer_ensure_setup(false);
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if (!gd->arch.clock_rate) {
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/*
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* Use the clock frequency specified in the
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* device tree as last resort
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*/
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if (!uc_priv->clock_rate)
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panic("TSC frequency is ZERO");
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} else {
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uc_priv->clock_rate = gd->arch.clock_rate;
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}
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return 0;
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}
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unsigned long notrace timer_early_get_rate(void)
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{
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/*
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* When TSC timer is used as the early timer, be warned that the timer
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* clock rate can only be calibrated via some hardware ways. Specifying
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* it in the device tree won't work for the early timer.
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*/
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tsc_timer_ensure_setup(true);
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return gd->arch.clock_rate;
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}
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u64 notrace timer_early_get_count(void)
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{
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return rdtsc() - gd->arch.tsc_base;
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}
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static const struct timer_ops tsc_timer_ops = {
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.get_count = tsc_timer_get_count,
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};
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static const struct udevice_id tsc_timer_ids[] = {
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{ .compatible = "x86,tsc-timer", },
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{ }
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};
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U_BOOT_DRIVER(tsc_timer) = {
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.name = "tsc_timer",
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.id = UCLASS_TIMER,
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.of_match = tsc_timer_ids,
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.probe = tsc_timer_probe,
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.ops = &tsc_timer_ops,
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.flags = DM_FLAG_PRE_RELOC,
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};
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