From: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx> Only if bus master activity is going on at the present, we should avoid entering C3-type sleep, as it might be a faulty transition. As long as the bm_activity bitmask was based on the number of calls to the ACPI idle function, looking at previous moments made sense. Now, with it being based on what happened this jiffy, looking at this jiffy should be sufficient. Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx> Cc: <linux-acpi@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxx> --- drivers/acpi/processor_idle.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff -puN drivers/acpi/processor_idle.c~acpi-c-states-only-demote-on-current-bus-mastering-activity drivers/acpi/processor_idle.c --- a/drivers/acpi/processor_idle.c~acpi-c-states-only-demote-on-current-bus-mastering-activity +++ a/drivers/acpi/processor_idle.c @@ -290,10 +290,10 @@ static void acpi_processor_idle(void) pr->power.bm_check_timestamp = jiffies; /* - * Apply bus mastering demotion policy. Automatically demote + * If bus mastering is or was active this jiffy, demote * to avoid a faulty transition. Note that the processor * won't enter a low-power state during this call (to this - * funciton) but should upon the next. + * function) but should upon the next. * * TBD: A better policy might be to fallback to the demotion * state (use it for this quantum only) istead of @@ -301,7 +301,8 @@ static void acpi_processor_idle(void) * qualification. This may, however, introduce DMA * issues (e.g. floppy DMA transfer overrun/underrun). */ - if (pr->power.bm_activity & cx->demotion.threshold.bm) { + if ((pr->power.bm_activity & 0x1) && + cx->demotion.threshold.bm) { local_irq_enable(); next_state = cx->demotion.state; goto end; _ - 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