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Re: [linux-pm] [PATCH 46/76] ACPI: Introduce ACPI D3_COLD state support

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On Friday, March 30, 2012, Len Brown wrote:
> From: Zhang Rui <rui.zhang@xxxxxxxxx>
> 
> If a device has _PR3, it means the device supports D3_COLD.
> Add the ability to validate and enter D3_COLD state in ACPI.

This patch is wrong, IMO.

Namely, _PR3 lists power resources that are supposed to be "on"
in D3, which means that in that state the device is not completely
off, so this must be D3_hot and not D3_cold.

So. _PR3 means D3_hot is supported.  D3_cold, on the other hand,
is always supported, although it may not be accessible through any
direct software action (for example, it may be necessary to power
down a bus to put devices on it into D3_cold).

Thanks,
Rafael


> Signed-off-by: Zhang Rui <rui.zhang@xxxxxxxxx>
> Signed-off-by: Lin Ming <ming.m.lin@xxxxxxxxx>
> Signed-off-by: Len Brown <len.brown@xxxxxxxxx>
> ---
>  drivers/acpi/power.c |    4 ++--
>  drivers/acpi/scan.c  |    7 +++++++
>  2 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/acpi/power.c b/drivers/acpi/power.c
> index 9ac2a9f..0d681fb 100644
> --- a/drivers/acpi/power.c
> +++ b/drivers/acpi/power.c
> @@ -500,14 +500,14 @@ int acpi_power_transition(struct acpi_device *device, int state)
>  {
>  	int result;
>  
> -	if (!device || (state < ACPI_STATE_D0) || (state > ACPI_STATE_D3))
> +	if (!device || (state < ACPI_STATE_D0) || (state > ACPI_STATE_D3_COLD))
>  		return -EINVAL;
>  
>  	if (device->power.state == state)
>  		return 0;
>  
>  	if ((device->power.state < ACPI_STATE_D0)
> -	    || (device->power.state > ACPI_STATE_D3))
> +	    || (device->power.state > ACPI_STATE_D3_COLD))
>  		return -ENODEV;
>  
>  	/* TBD: Resources must be ordered. */
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 8ab80ba..571396c 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -885,6 +885,13 @@ static int acpi_bus_get_power_flags(struct acpi_device *device)
>  				acpi_bus_add_power_resource(ps->resources.handles[j]);
>  		}
>  
> +		/* The exist of _PR3 indicates D3Cold support */
> +		if (i == ACPI_STATE_D3) {
> +			status = acpi_get_handle(device->handle, object_name, &handle);
> +			if (ACPI_SUCCESS(status))
> +				device->power.states[ACPI_STATE_D3_COLD].flags.valid = 1;
> +		}
> +
>  		/* Evaluate "_PSx" to see if we can do explicit sets */
>  		object_name[2] = 'S';
>  		status = acpi_get_handle(device->handle, object_name, &handle);
> 

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