Re: [Xen-devel] [PATCH] ACPI: Add fixups for AMD P-state figures.

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 03/05/2013 02:45 PM, Konrad Rzeszutek Wilk wrote:
> This a copy-n-paste from two Linux git commits:
>
> - f594065faf4f9067c2283a34619fc0714e79a98d
>    ACPI: Add fixups for AMD P-state figures
> - 9855d8ce41a7801548a05d844db2f46c3e810166
>    ACPI: Check MSR valid bit before using P-state frequencies
>
> The issue is that "some AMD systems may round the frequencies in
> ACPI tables to 100MHz boundaries. We canobtain the real
> frequencies from MSRs, so add a quirk to fix these frequencies up
> on AMD systems." (from f594065..)
>
> In discussion (around 9855d8..) "it turned out that indeed real
> HW/BIOSes may choose to not set the valid bit and thus mark the
> P-state as invalid. So this could be considered a fix for broken
> BIOSes that also works around the issue on Xen." (from 9855d8..)
>
> I've tested it under Dell Inc. PowerEdge T105 /0RR825, BIOS 1.3.2
> 08/20/2008 where this quirk can indeed be observed.
>
> CC: stefan.bader@xxxxxxxxxxxxx
> CC: bp@xxxxxxx
> CC: borislav.ostrovsky@xxxxxxxxxx
boris.ostrovsky@xxxxxxxxxx

> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
>   xen/arch/x86/acpi/cpufreq/powernow.c | 38 ++++++++++++++++++++++++++++++++++++
>   1 file changed, 38 insertions(+)
>
> diff --git a/xen/arch/x86/acpi/cpufreq/powernow.c 
> b/xen/arch/x86/acpi/cpufreq/powernow.c
> index a9b7792..0eaa16c 100644
> --- a/xen/arch/x86/acpi/cpufreq/powernow.c
> +++ b/xen/arch/x86/acpi/cpufreq/powernow.c
> @@ -146,7 +146,43 @@ static int powernow_cpufreq_target(struct cpufreq_policy 
> *policy,
>   
>       return 0;
>   }
> +#define MSR_AMD_PSTATE_DEF_BASE     0xc0010064
There is MSR_PSTATE_DEF_BASE at the top of this file which is the same 
thing.
> +static void amd_fixup_frequency(struct xen_processor_px *px)
> +{
> +       u32 hi, lo, fid, did;
> +       int index = px->control & 0x00000007;
> +
> +       if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
> +               return;
> +
> +       if ((boot_cpu_data.x86 == 0x10 && boot_cpu_data.x86_model < 10)
> +           || boot_cpu_data.x86 == 0x11) {
> +               rdmsr(MSR_AMD_PSTATE_DEF_BASE + index, lo, hi);
> +        /*
> +         * MSR C001_0064+:
> +         * Bit 63: PstateEn. Read-write. If set, the P-state is valid.
> +         */
> +        if (!(hi & (1UL << 31)))
> +            return;
Identation is off.

-boris

> +
> +               fid = lo & 0x3f;
> +               did = (lo >> 6) & 7;
> +               if (boot_cpu_data.x86 == 0x10)
> +                       px->core_frequency = (100 * (fid + 0x10)) >> did;
> +               else
> +                       px->core_frequency = (100 * (fid + 8)) >> did;
> +       }
> +}
> +
> +static void amd_fixup_freq(struct processor_performance *perf)
> +{
>   
> +    int i;
> +
> +    for (i = 0; i < perf->state_count; i++)
> +        amd_fixup_frequency(&perf->states[i]);
> +
> +}
>   static int powernow_cpufreq_verify(struct cpufreq_policy *policy)
>   {
>       struct acpi_cpufreq_data *data;
> @@ -253,6 +289,8 @@ static int powernow_cpufreq_cpu_init(struct cpufreq_policy 
> *policy)
>   
>       policy->governor = cpufreq_opt_governor ? : CPUFREQ_DEFAULT_GOVERNOR;
>   
> +    amd_fixup_freq(perf);
> +
>       /* table init */
>       for (i = 0; i < perf->state_count && i <= max_hw_pstate; i++) {
>           if (i > 0 && perf->states[i].core_frequency >=

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