From: Arjan van de Ven <arjan@xxxxxxxxxxxxx> Taken from http://bugzilla.kernel.org/show_bug.cgi?id=8703 Cc: Dag Bakke <dag@xxxxxxxxx> Cc: Len Brown <lenb@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- drivers/acpi/processor_idle.c | 24 ++++++++++++++++++++++-- 1 files changed, 22 insertions(+), 2 deletions(-) diff -puN drivers/acpi/processor_idle.c~acpi-enable-c3-power-state-on-dell-inspiron-8200 drivers/acpi/processor_idle.c --- a/drivers/acpi/processor_idle.c~acpi-enable-c3-power-state-on-dell-inspiron-8200 +++ a/drivers/acpi/processor_idle.c @@ -67,6 +67,8 @@ ACPI_MODULE_NAME("processor_idle"); #define C2_OVERHEAD 1 /* 1us */ #define C3_OVERHEAD 1 /* 1us */ +static int forced_c3; + void acpi_max_cstate_changed(void) { /* Driver will reset devices' max cstate limit */ @@ -115,6 +117,20 @@ static int set_max_cstate(struct dmi_sys return 0; } +/* + * Some (Dell) machines have a too large C3 latency set, but it still works completely. + * Dell provides a driver for other operating systems to hack around this bug, so we know + * it's safe. + */ +static int dmi_force_c3(struct dmi_system_id *id) +{ + forced_c3 = 1; + + printk(KERN_NOTICE PREFIX "%s detected - Force enabling C3.", id->ident); + + return 0; +} + /* Actually this shouldn't be __cpuinitdata, would be better to fix the callers to only run once -AK */ static struct dmi_system_id __cpuinitdata processor_power_dmi_table[] = { @@ -173,6 +189,9 @@ static struct dmi_system_id __cpuinitdat DMI_MATCH(DMI_BIOS_VENDOR,"Phoenix Technologies LTD"), DMI_MATCH(DMI_BIOS_VERSION,"SHE845M0.86C.0013.D.0302131307")}, (void *)2}, + { dmi_force_c3, "Dell Inspiron 8200", { + DMI_MATCH(DMI_SYS_VENDOR,"Dell Computer Corporation"), + DMI_MATCH(DMI_PRODUCT_NAME,"Inspiron 8200") }, NULL}, {}, }; @@ -487,11 +506,12 @@ static void acpi_processor_power_verify_ * C3 latency must be less than or equal to 1000 * microseconds. */ - else if (cx->latency > ACPI_PROCESSOR_MAX_C3_LATENCY) { + if (cx->latency > ACPI_PROCESSOR_MAX_C3_LATENCY && !forced_c3) { ACPI_DEBUG_PRINT((ACPI_DB_INFO, "latency too large [%d]\n", cx->latency)); return; - } + } else if (forced_c3) + cx->latency = ACPI_PROCESSOR_MAX_C3_LATENCY; /* * PIIX4 Erratum #18: We don't support C3 when Type-F (fast) _ - 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
