Re: [PATCH] drivers/cpufreq: Warn user when powernow-k8 tries to fall back to acpi-cpufreq and it is unavailable.

Borislav Petkov
2013-01-18T19:36:56Z

On Fri, Jan 18, 2013 at 07:06:59PM +0000, Matthew Garrett wrote:
> On Fri, Jan 18, 2013 at 08:00:21PM +0100, Borislav Petkov wrote:
>
> > ##################################################################################
> > # x86 drivers.
> > # Link order matters. K8 is preferred to ACPI because of firmware bugs in early
> > # K8 systems.
> > ...
> >
> > Great. :(
>
> The only case I can see this hitting would be if the platform is using
> system IO rather than fixed hardware functionality. Easiest thing to do
> there would be something like this:
>
> diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
> index 0d048f6..8b466d5 100644
> --- a/drivers/cpufreq/acpi-cpufreq.c
> +++ b/drivers/cpufreq/acpi-cpufreq.c
> @@ -762,6 +762,11 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
>
> switch (perf->control_register.space_id) {
> case ACPI_ADR_SPACE_SYSTEM_IO:
> + if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
> + pr_debug("Old AMD systems must use native drivers\n");
> + result = -ENODEV;
> + goto err_unreg;
> + }
> pr_debug("SYSTEM IO addr space\n");
> data->cpu_feature = SYSTEM_IO_CAPABLE;
> break;

Ok, how much can we rely on ACPI to have this ACPI_ADR_SPACE_SYSTEM_IO
properly set on K8? Because the thing is, we want to use acpi-cpufreq on
F10h onwards and leave powernow-k8 to K8s.

So we're purely relying on ->control_register.space_id being
ACPI_ADR_SPACE_SYSTEM_IO on *all* K8s. And with the history BIOS has, I
don't trust it a single bit. Other than that, this could work...

Thanks.