From 644f17ad7fc12768cd619532383343e514eab2ac Mon Sep 17 00:00:00 2001 From: Mika Westerberg Date: Thu, 10 Oct 2013 13:28:46 +0300 Subject: ACPI / PM: allow child devices to ignore parent power state Some serial buses like I2C and SPI don't require that the parent device is in D0 before any of its children transitions to D0, but instead the parent device can control its own power independently from the children. This does not follow the ACPI specification as it requires the parent to be powered on before its children. However, Windows seems to ignore this requirement so I think we can do the same in Linux. Implement this by adding a new power flag 'ignore_parent' to struct acpi_device. If this flag is set the ACPI core ignores checking of the parent device power state when the device is powered on/off. Signed-off-by: Mika Westerberg Signed-off-by: Rafael J. Wysocki --- drivers/acpi/device_pm.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'drivers/acpi/device_pm.c') diff --git a/drivers/acpi/device_pm.c b/drivers/acpi/device_pm.c index 59d3202f6b36..ca723a4c120a 100644 --- a/drivers/acpi/device_pm.c +++ b/drivers/acpi/device_pm.c @@ -118,9 +118,10 @@ int acpi_device_get_power(struct acpi_device *device, int *state) /* * If we were unsure about the device parent's power state up to this * point, the fact that the device is in D0 implies that the parent has - * to be in D0 too. + * to be in D0 too, except if ignore_parent is set. */ - if (device->parent && device->parent->power.state == ACPI_STATE_UNKNOWN + if (!device->power.flags.ignore_parent && device->parent + && device->parent->power.state == ACPI_STATE_UNKNOWN && result == ACPI_STATE_D0) device->parent->power.state = ACPI_STATE_D0; @@ -177,7 +178,8 @@ int acpi_device_set_power(struct acpi_device *device, int state) acpi_power_state_string(state)); return -ENODEV; } - if (device->parent && (state < device->parent->power.state)) { + if (!device->power.flags.ignore_parent && + device->parent && (state < device->parent->power.state)) { dev_warn(&device->dev, "Cannot transition to power state %s for parent in %s\n", acpi_power_state_string(state), -- cgit v1.2.3