On Thu, Mar 24, 2016 at 5:07 AM, Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx> wrote: > There are several reports of freeze on enabling HWP (Hardware PStates) > feature on Skylake based systems by Intel P states driver. The root > cause is identified as the HWP interrupts causing BIOS code to freeze. > HWP interrupts uses thermal LVT. > Linux natively handles thermal interrupts, but in Skylake based systems > SMM will take control of thermal interrupts. This is a problem for several > reasons: > - It is freezing in BIOS when tries to handle thermal interrupt, which > will require BIOS upgrade > - With SMM handling thermal we loose all the reporting features of > Linux arch/x86/kernel/cpu/mcheck/therm_throt driver > - Some thermal drivers like x86-package-temp driver depends on the thermal > threshold interrupts > - The HWP interrupts are useful for debugging and tuning performance > > So we need native handling of thermal interrupts. This requires some > way to inform SMM that OS can handle thermal interrupts. This can be > done by using _OSC/_PDC under processor scope very early in ACPI > initialization flow. > The bit 12 of _OSC/_PDC in processor scope defines whether OS supports > handling of native interrupts for Collaborative Processor Performance > Control (CPPC) notifications. Since HWP is a implementation of CPPC, > setting this bit is equivalent to inform SMM that OS is capable of > handling thermal interrupts. > Refer to this document for details on _OSC/_PDC > http://www.intel.com/content/www/us/en/standards/processor-vendor- > specific-acpi-specification.html > > This change introduces a new function acpi_early_processor_set_osc(), > which walks acpi name space and finds acpi processor object and > set capability via _OSC method. > > Also this change writes HWP status bits to 0 to clear any HWP status > bits in intel_thermal_interrupt(). > > Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx> I've queued it up, but I have modified the subject and the changelog and renamed the new function. Please have a look at http://git.kernel.org/cgit/linux/kernel/git/rafael/linux-pm.git/commit/?h=bleeding-edge&id=42341f87ba1bee4c5be95038c24abb69cbcf361a and let me know if it makes sense to you. Thanks, Rafael -- 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
