[U-Boot] [PATCH v2 2/4] x86: Do TSC MSR calibration only for known/supported CPUs
Bin Meng
bmeng.cn at gmail.com
Wed Nov 12 02:16:06 CET 2014
Hi Simon,
On Wed, Nov 12, 2014 at 12:10 AM, Simon Glass <sjg at chromium.org> wrote:
> Hi Bin,
>
> On 11 November 2014 01:25, Bin Meng <bmeng.cn at gmail.com> wrote:
>> Hi Simon,
>>
>> On Tue, Nov 11, 2014 at 2:54 AM, Simon Glass <sjg at chromium.org> wrote:
>>> Hi Bin,
>>>
>>> On 9 November 2014 07:19, Bin Meng <bmeng.cn at gmail.com> wrote:
>>>> Using MSR_PLATFORM_INFO (0xCE) to calibrate TSR will cause #GP on
>>>> processors which do not have this MSR. Instead only doing the MSR
>>>> calibration for known/supported CPUs.
>>>>
>>>> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
>>>> Acked-by: Simon Glass <sjg at chromium.org>
>>>> Tested-by: Simon Glass <sjg at chromium.org>
>>>> ---
>>>> arch/x86/lib/tsc_timer.c | 116 ++++++++++++++++++++++++++++++++++++++++++++---
>>>> 1 file changed, 109 insertions(+), 7 deletions(-)
>>>
>>> Applied to u-boot-x86/master, thanks!
>>>
>>> (Please see note below)
>>>
>>>>
>>>> diff --git a/arch/x86/lib/tsc_timer.c b/arch/x86/lib/tsc_timer.c
>>>> index 8b38702..fafbbfc 100644
>>>> --- a/arch/x86/lib/tsc_timer.c
>>>> +++ b/arch/x86/lib/tsc_timer.c
>>>> @@ -1,6 +1,9 @@
>>>> /*
>>>> * 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+
>>>> */
>>>>
>>>> @@ -12,8 +15,108 @@
>>>> #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 */
>>>> + u8 msr_plat; /* 1: use MSR_PLATFORM_INFO, 0: MSR_IA32_PERF_STATUS */
>>>> + 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 } },
>>>> + /* 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 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;
>>>> +
>>>> + /* 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;
>>>> +}
>>>> +
>>>> void timer_set_base(u64 base)
>>>> {
>>>> gd->arch.tsc_base = base;
>>>> @@ -34,17 +137,16 @@ u64 __attribute__((no_instrument_function)) get_ticks(void)
>>>> return now_tick - gd->arch.tsc_base;
>>>> }
>>>>
>>>> -#define PLATFORM_INFO_MSR 0xce
>>>> -
>>>> /* Get the speed of the TSC timer in MHz */
>>>> 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;
>>>> +
>>>> + fast_calibrate = try_msr_calibrate_tsc();
>>>> + if (!fast_calibrate)
>>>> + panic("TSC frequency is ZERO");
>>>>
>>>> - /* 100MHz times Max Non Turbo ratio */
>>>> - ratio = (platform_info >> 8) & 0xff;
>>>> - return 100 * ratio;
>>>
>>> What happens for platforms that have this MSR? Do we ignore it now?
>>> For my current platform this code is needed.
>>
>> In Linux the MSR calibration is only available on several Atom
>> platforms. If that fails, it falls back to use fast PIT calibration.
>> However, I think you can add an entry in the freq_desc_tables[] for
>> your platform if you want to use MSR calibration.
>
> I can add exceptions, but I wonder why this fails on my platform? Is
> your method supposed to work on any platform?
Which one fails? Do you mean the quick_pit_calibrate() fails? Is that
because your platform does not has the legacy 8254 integrated?
Regards,
Bin
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