arch/ia64/kernel/cpufreq/acpi-cpufreq.c currently makes direct calls to PAL_SET_PSTATE. Section 8.4.4.1 (_PCT) of the 3.0 ACPI spec says: OSPM performs processor performance transitions by writing the performance state-specific control value to a Performance Control Register (PERF_CTRL). According to one of our architecture guys, this means we really ought to have an OpRegion driver that encapsulates the PAL_SET_PSTATE call. I guess _PCT would return an acpi_generic_address in the FFixedHW address space, and we would use acpi_hw_low_level_read() and acpi_hw_low_level_write() to do the accesses (those functions would need to be extended to support additional OpRegions, or maybe I'm looking in the wrong place). This sort of makes sense to me, because it would mean this part of acpi-cpufreq wouldn't need to be ia64-specific. On x86, I suppose _PCT would return a ACPI_ADR_SPACE_SYSTEM_IO address, and acpi_processor_set_performance() could use acpi_hw_low_level_write() instead of its own acpi_processor_write_port(). But I haven't seen anything resembling an ACPI FFH OpRegion driver for Linux, or even a spec (e.g., a definition of what the FFH address space contains) that would allow such a driver to be written. Any hints on what the future might hold in this area? 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
