>-----Original Message----- >From: Bjorn Helgaas [mailto:bjorn.helgaas@xxxxxx] >Sent: Tuesday, October 24, 2006 10:51 AM >To: Pallipadi, Venkatesh >Cc: linux-acpi@xxxxxxxxxxxxxxx; linux-ia64@xxxxxxxxxxxxxxx >Subject: Re: ia64 acpi-cpufreq driver > >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? > Yes. As it is today, acpi-cpufreq contains FFH driver functionality in itself. It calls acpi and cpufreq arch-independent interfaces but implements FFH internally. By, FFH driver do you mean to handle FFH related functions only for P-states or something that can handle all FFH functions (like C-states, etc). I don't see any other kernel part/or driver will use this particular PAL_GET_PSTATE and PAL_SET_PSTATE intefaces. So, my feeling is we don't need a separate FFH driver. Thanks, Venki - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
