On Friday, September 07, 2012, Aaron Lu wrote:
> On 09/07/2012 07:46 PM, Rafael J. Wysocki wrote:
> >> Yes, on a test system, when I try to put a device into D3 cold and ACPI
> >> will complain that I can't due to its parent is in a even lower power
> >> state UNKNOWN(255), this parent device is power manageable but has no
> >> _PSC and _PRx defined.
> >
> > Perhaps we can force _PS0 for such devices to start with, so that we know
> > for sure that the initial state is D0?
>
> Sounds good, I'll update the patch, thanks for the advice.
Actually, I suppose we can do something like the appended patch instead.
I wonder if it works around the particular problem you're seeing?
Rafael
---
drivers/acpi/bus.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
Index: linux/drivers/acpi/bus.c
===================================================================
--- linux.orig/drivers/acpi/bus.c
+++ linux/drivers/acpi/bus.c
@@ -229,7 +229,16 @@ static int __acpi_bus_get_power(struct a
result = psc;
}
/* The test below covers ACPI_STATE_UNKNOWN too. */
- if (result <= ACPI_STATE_D2) {
+ if (result == ACPI_STATE_D0) {
+ /*
+ * 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.
+ */
+ if (device->parent
+ && device->parent->power.state == ACPI_STATE_UNKNOWN)
+ device->parent->power.state = ACPI_STATE_D0;
+ } else if (result <= ACPI_STATE_D2) {
; /* Do nothing. */
} else if (device->power.flags.power_resources) {
int error = acpi_power_get_inferred_state(device, &result);
--
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