Re: [PATCH] ACPI / PM: Add check preventing transitioning to non-D0 state from D3.

[Peter Wu <lekensteyn@gmail.com>]

Hi Lv Zheng,

I encounter a regression with your patch (Linux 3.8-rc5). On my Nvidia Optimus 
laptop, I use the bbswitch[1] kernel module to trigger a _PS3 ACPI method call 
to turn the video card off.

After this patch, I got the following in my kernel log:

    pci 0000:01:00.0: Refused to change power state, currently in D0
    ACPI: Cannot transition to non-D0 state from D3
    bbswitch: Succesfully loaded. Discrete card 0000:01:00.0 is on

The expected output would be "Discrete card 0000:01:00.0 is  off". Printing the 
contents of (acpi_device) device->power.state shows FF (ACPI_STATE_UNKNOWN). 
Should this condition be excluded from your check or is my hacky module 
outdated?

I currently workaround this issue by checking for ACPI_STATE_UNKNOWN. If that 
is the value, I assume on (overwrite device->power.state with ACPI_STATE_D0). 
Then I call pci_set_power_state(pci_dev, PCI_D3cold).

Regards,
Peter

 [1]: https://github.com/Bumblebee-Project/bbswitch

On Thursday 15 November 2012 12:25:01 Lv Zheng wrote:
> No power transitioning from D3 state to a non-D0 state is allowed.
> This patch also cleans up device power updating code in the
> acpi_device_set_power() as it should already been updated in the
> acpi_power_transition().
> 
> Signed-off-by: Lv Zheng <lv.zheng@intel.com>
> ---
>  drivers/acpi/bus.c |    7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
> index 07a20ee..12c1b51 100644
> --- a/drivers/acpi/bus.c
> +++ b/drivers/acpi/bus.c
> @@ -293,6 +293,12 @@ int acpi_device_set_power(struct acpi_device *device,
> int state) " state than parent\n");
>  		return -ENODEV;
>  	}
> +	if (device->parent->power.state >= ACPI_STATE_D3_HOT &&
> +	    state != ACPI_STATE_D0) {
> +		printk(KERN_WARNING PREFIX
> +			      "Cannot transition to non-D0 state from D3\n");
> +		return -ENODEV;
> +	}
> 
>  	/* For D3cold we should execute _PS3, not _PS4. */
>  	if (state == ACPI_STATE_D3_COLD)
> @@ -341,7 +347,6 @@ int acpi_device_set_power(struct acpi_device *device,
> int state) "Device [%s] failed to transition to %s\n",
>  			      device->pnp.bus_id, state_string(state));
>  	else {
> -		device->power.state = state;
>  		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
>  				  "Device [%s] transitioned to %s\n",
>  				  device->pnp.bus_id, state_string(state)));