On Mon 2010-07-26 19:51:29, Len Brown wrote: > From: Len Brown <len.brown@xxxxxxxxx> > > upstream 718be4aaf3613cf7c2d097f925abc3d3553c0605 > > It turns out that there is a bit in the _CST for Intel FFH C3 > that tells the OS if we should be checking BM_STS or not. > > Linux has been unconditionally checking BM_STS. > If the chip-set is configured to enable BM_STS, > it can retard or completely prevent entry into > deep C-states -- as illustrated by turbostat: > > http://userweb.kernel.org/~lenb/acpi/utils/pmtools/turbostat/ > > ref: Intel Processor Vendor-Specific ACPI Interface Specification > table 4 "_CST FFH GAS Field Encoding" > Bit 1: Set to 1 if OSPM should use Bus Master avoidance for this C-state > > https://bugzilla.kernel.org/show_bug.cgi?id=15886 > > Signed-off-by: Len Brown <len.brown@xxxxxxxxx> This is better than cpu whitelist. Thanks! > --- > > this backport applies cleanly to 2.6.32.y. > It applies w/ a small offset to 2.6.33.y and 2.34.y > > > arch/x86/kernel/acpi/cstate.c | 9 +++++++++ > drivers/acpi/processor_idle.c | 2 +- > include/acpi/processor.h | 3 ++- > 3 files changed, 12 insertions(+), 2 deletions(-) > > Index: linux-2.6.32.y/arch/x86/kernel/acpi/cstate.c > =================================================================== > --- linux-2.6.32.y.orig/arch/x86/kernel/acpi/cstate.c > +++ linux-2.6.32.y/arch/x86/kernel/acpi/cstate.c > @@ -145,6 +145,15 @@ int acpi_processor_ffh_cstate_probe(unsi > percpu_entry->states[cx->index].eax = cx->address; > percpu_entry->states[cx->index].ecx = MWAIT_ECX_INTERRUPT_BREAK; > } > + > + /* > + * For _CST FFH on Intel, if GAS.access_size bit 1 is cleared, > + * then we should skip checking BM_STS for this C-state. > + * ref: "Intel Processor Vendor-Specific ACPI Interface Specification" > + */ > + if ((c->x86_vendor == X86_VENDOR_INTEL) && !(reg->access_size & 0x2)) > + cx->bm_sts_skip = 1; > + > return retval; > } > EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_probe); > Index: linux-2.6.32.y/drivers/acpi/processor_idle.c > =================================================================== > --- linux-2.6.32.y.orig/drivers/acpi/processor_idle.c > +++ linux-2.6.32.y/drivers/acpi/processor_idle.c > @@ -962,7 +962,7 @@ static int acpi_idle_enter_bm(struct cpu > if (acpi_idle_suspend) > return(acpi_idle_enter_c1(dev, state)); > > - if (acpi_idle_bm_check()) { > + if (!cx->bm_sts_skip && acpi_idle_bm_check()) { > if (dev->safe_state) { > dev->last_state = dev->safe_state; > return dev->safe_state->enter(dev, dev->safe_state); > Index: linux-2.6.32.y/include/acpi/processor.h > =================================================================== > --- linux-2.6.32.y.orig/include/acpi/processor.h > +++ linux-2.6.32.y/include/acpi/processor.h > @@ -48,7 +48,7 @@ struct acpi_power_register { > u8 space_id; > u8 bit_width; > u8 bit_offset; > - u8 reserved; > + u8 access_size; > u64 address; > } __attribute__ ((packed)); > > @@ -74,6 +74,7 @@ struct acpi_processor_cx { > u32 power; > u32 usage; > u64 time; > + u8 bm_sts_skip; > struct acpi_processor_cx_policy promotion; > struct acpi_processor_cx_policy demotion; > char desc[ACPI_CX_DESC_LEN]; > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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
