Re: ia64 acpi-cpufreq driver

Bjorn Helgaas
2006-10-24T17:50:30Z

On Monday 23 October 2006 22:46, Pallipadi, Venkatesh wrote:
> Actually it is slightly different from low_level_read and write.
> Generic ACPI definition of ACPI PERF_CTRL and PERF_STATUS define
> them as if they are registers. But, with FfixedHW, ACPI allows
> architectures to implement this functionality in a native way.
> Just like x86 implements FfixedHW based P-state support in 16 bits
> of some known MSR (Note the register field itself in _PCT is not used)
> or FFH C-states are supported by native instructions like "hlt",
> "monitor-mwait".
>
> So, when firmware tells P-state are FFH, OS will look at the hardware
> and processor information and use appropriate native interfaces.
> In this case, appropriate native interface is PAL_GET_PSTATE
> and PAL_SET_PSTATE.

Clearly ia64 ultimately has to use PAL_SET_PSTATE. My question
is, does the PAL_SET_PSTATE call belong in acpi-cpufreq, or does
it belong in the FFH driver?

I think it belongs in the latter, because the OSPM can be more
generic if the architecture-specific stuff is in the FFH driver.

Another way to ask this is, if ia64 had an FFH driver, who would
use it? I assume acpi-cpufreq would be one user. If so, what
interface would acpi-cpufreq use to access FFH?

Bjorn