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 - 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
