Re: [PATCH 4/8] x86/mrst: change clock selection logic to support medfield

Thomas Gleixner
2010-05-11T14:36:56Z

On Fri, 7 May 2010, Jacob Pan wrote:

> From: Jacob Pan <jacob.jun.pan@intel.com>
>
> Penwell has added always on lapic timers and tsc, we want to treat
> it as a variant of moorestown so that one binary kernel can boot on both.
> this patch added clock selction logic so that platform code can set up the
> optimal configuration for both moorestown and medfield.
>
> This patch will also mark Penwell TSC reliable, thus no need for
> watchdog clocksource to monitor it.
>
> Signed-off-by: Alek Du <alek.du@intel.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@intel.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> ---
> arch/x86/include/asm/mrst.h | 30 +++++++++++
> arch/x86/kernel/mrst.c | 119 ++++++++++++++++++++++++++++++++++++++----
> 2 files changed, 137 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/include/asm/mrst.h b/arch/x86/include/asm/mrst.h
> index 451d30e..3054407 100644
> --- a/arch/x86/include/asm/mrst.h
> +++ b/arch/x86/include/asm/mrst.h
> @@ -11,7 +11,37 @@
> #ifndef _ASM_X86_MRST_H
> #define _ASM_X86_MRST_H
> extern int pci_mrst_init(void);
> +extern unsigned int calibration_result;

Yuck, why is this in a mrst specific header ?

> +
> +#define MRST_TIMER_DEFAULT 0
> +#define MRST_TIMER_APBT_ONLY 1
> +#define MRST_TIMER_LAPIC_APBT 2

enum please, also

> +/**
> + * the clockevent devices on Moorestown/Medfield can be APBT or LAPIC clock,
> + * cmdline option x86_mrst_timer can be used to override the configuration
> + * to prefer one or the other.
> + * at runtime, there are basically three timer configurations:
> + * 1. per cpu apbt clock only
> + * 2. per cpu always-on lapic clocks only, this is Penwell/Medfield only
> + * 3. per cpu lapic clock (C3STOP) and one apbt clock, with broadcast.
> + *
> + * by default (without cmdline option), platform code first detects cpu type
> + * to see if we are on lincroft or penwell, then set up both lapic or apbt
> + * clocks accordingly.
> + * i.e. by default, medfield uses configuration #2, moorestown uses #1.
> + * config #3 is supported but not recommended on medfield.
> + *
> + * rating and feature summary:
> + * lapic (with C3STOP) --------- 100
> + * apbt (always-on) ------------ 110

apbt sucks performance wise, so why do you consider it a better
choice than lapic + broadcast ?

> + * lapic (always-on,ARAT) ------ 150
> + */
> +
> +int mrst_timer_options __cpuinitdata;
> +
> static u32 sfi_mtimer_usage[SFI_MTMR_MAX_NUM];
> static struct sfi_timer_table_entry sfi_mtimer_array[SFI_MTMR_MAX_NUM];
> +static u32 mrst_cpu_chip;
> int sfi_mtimer_num;
>
> struct sfi_rtc_table_entry sfi_mrtc_array[SFI_MRTC_MAX];
> @@ -167,15 +191,16 @@ int __init sfi_parse_mrtc(struct sfi_table_header *table)
> return 0;
> }
>
> -/*
> - * the secondary clock in Moorestown can be APBT or LAPIC clock, default to
> - * APBT but cmdline option can also override it.
> - */
> static void __cpuinit mrst_setup_secondary_clock(void)
> {
> - /* restore default lapic clock if disabled by cmdline */
> - if (disable_apbt_percpu)
> - return setup_secondary_APIC_clock();
> + if ((mrst_timer_options == MRST_TIMER_APBT_ONLY))
> + return apbt_setup_secondary_clock();
> + if (cpu_has(&current_cpu_data, X86_FEATURE_ARAT)
> + || (mrst_timer_options == MRST_TIMER_LAPIC_APBT)) {
> + pr_info("using lapic timers for secondary clock\n");
> + setup_secondary_APIC_clock();
> + return;

The logic is confusing.

> + }
> apbt_setup_secondary_clock();
> }
>
> @@ -183,9 +208,45 @@ static unsigned long __init mrst_calibrate_tsc(void)
> {
> unsigned long flags, fast_calibrate;
>
> - local_irq_save(flags);
> - fast_calibrate = apbt_quick_calibrate();
> - local_irq_restore(flags);
> + if (mrst_cpu_chip == MRST_CPU_CHIP_PENWELL) {
> + u32 lo, hi, ratio, fsb;
> +
> + rdmsr(MSR_IA32_PERF_STATUS, lo, hi);
> + pr_debug("IA32 perf status is 0x%x, 0x%0x\n", lo, hi);
> + ratio = (hi >> 8) & 0x1f;
> + pr_debug("ratio is %d\n", ratio);
> + if (!ratio) {
> + pr_err("read a zero ratio, should be incorrect!\n");
> + pr_err("force tsc ratio to 16 ...\n");
> + ratio = 16;
> + }

This is not Penwell specific at all. The ratio can be read out on all
Core based CPUs either from MSR_PLATFORM_ID[12:8] or
MSR_PERF_STAT[44:40] depending on XE operation enabled
(MSR_PERF_STAT[31] == 1)

This should be made general available and not burried into the mrst
code.

> + rdmsr(MSR_FSB_FREQ, lo, hi);
> + if ((lo & 0x7) == 0x7)
> + fsb = PENWELL_FSB_FREQ_83SKU;
> + else
> + fsb = PENWELL_FSB_FREQ_100SKU;

I guess the 111 is Penwell/MRST specific, right ?

According to SDM we have anyway different results for the various CPU
families, but we should utilize this in a generic way and have the
translation tables for the various CPUs in one place.

> + fast_calibrate = ratio * fsb;
> + pr_debug("read penwell tsc %lu khz\n", fast_calibrate);
> + calibration_result = fsb * 1000 / HZ;
> + /* mark tsc clocksource as reliable */
> + set_cpu_cap(&boot_cpu_data, X86_FEATURE_TSC_RELIABLE);
> + } else {
> + /**
> + * TODO: calibrate lapic timer with apbt, if we use apbt only,
> + * there is no need to calibrate lapic timer, since they are
> + * not used.
> + * if we use lapic timers and apbt, the default calibration
> + * should work, since we have the global clockevent setup.
> + * but it would be more efficient if we combine the lapic timer
> + * with tsc calibration.
> + */
> + local_irq_save(flags);
> + fast_calibrate = apbt_quick_calibrate();
> + local_irq_restore(flags);
> + }
> +
> + pr_info("tsc lapic calibration results %lu %d\n",
> + fast_calibrate, calibration_result);
>
> if (fast_calibrate)
> return fast_calibrate;
> @@ -195,6 +256,11 @@ static unsigned long __init mrst_calibrate_tsc(void)
>
> void __init mrst_time_init(void)
> {
> + /* if cpu is penwell, lapic timer will be used by default */
> + if ((mrst_cpu_chip == MRST_CPU_CHIP_PENWELL) &&
> + (mrst_timer_options == MRST_TIMER_DEFAULT))
> + return;
> +
> sfi_table_parse(SFI_SIG_MTMR, NULL, NULL, sfi_parse_mtmr);
> pre_init_apic_IRQ0();
> apbt_time_init();
> @@ -211,11 +277,38 @@ void __init mrst_rtc_init(void)
> */
> static void __init mrst_setup_boot_clock(void)
> {
> - pr_info("%s: per cpu apbt flag %d \n", __func__, disable_apbt_percpu);
> - if (disable_apbt_percpu)
> + if (mrst_timer_options == MRST_TIMER_APBT_ONLY)
> + return;
> + if ((mrst_timer_options == MRST_TIMER_LAPIC_APBT)
> + || (mrst_cpu_chip == MRST_CPU_CHIP_PENWELL))
> setup_boot_APIC_clock();
> };
>
> +enum cpuid_regs {
> + CR_EAX = 0,
> + CR_ECX,
> + CR_EDX,
> + CR_EBX
> +};
> +
> +int mrst_identify_cpu(void)
> +{
> + u32 regs[4];
> +
> + cpuid(1, &regs[CR_EAX], &regs[CR_EBX], &regs[CR_ECX], &regs[CR_EDX]);

Yikes. From which Intel cookbook is this ?

Aside of that we have that info in boot_cpu_info already, don't we ?
So there is neither a requirement for the extra cpuid call nor for
the extra mrst_cpu_chip id magic.

> + if ((regs[CR_EAX] & PENWELL_FAMILY) == PENWELL_FAMILY)
> + mrst_cpu_chip = MRST_CPU_CHIP_PENWELL;
> + else
> + mrst_cpu_chip = MRST_CPU_CHIP_LINCROFT;

> + pr_debug("cpuid result %x\n", regs[CR_EAX]);
> + pr_info("Moorestown CPU %s identified\n",
> + (mrst_cpu_chip == MRST_CPU_CHIP_LINCROFT) ?
> + "Lincroft" : "Penwell");

Are we going to add one of those for each new family ? This is
really redundant bloat with no value.

> + return mrst_cpu_chip;
> +}
> +
> /*
> * Moorestown specific x86_init function overrides and early setup
> * calls.
> @@ -237,4 +330,6 @@ void __init x86_mrst_early_setup(void)
> x86_init.pci.fixup_irqs = x86_init_noop;
>
> legacy_pic = &null_legacy_pic;
> +
> + mrst_identify_cpu();
> }
> --
> 1.6.3.3
>