linux-kernel - Re: [RFC PATCH 1/6] ACPI: Introduce ACPI D3

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Message-Id: <201202132125.15537.rjw@sisk.pl>
Date:	Mon, 13 Feb 2012 21:25:15 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Lin Ming <ming.m.lin@...el.com>
Cc:	Zhang Rui <rui.zhang@...el.com>, Jeff Garzik <jgarzik@...ox.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Tejun Heo <tj@...nel.org>, Len Brown <lenb@...nel.org>,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	linux-scsi@...r.kernel.org, linux-pm@...r.kernel.org,
	ACPI Devel Mailing List <linux-acpi@...r.kernel.org>
Subject: Re: [RFC PATCH 1/6] ACPI: Introduce ACPI D3_COLD state support

On Monday, February 13, 2012, Lin Ming wrote:
> From: Zhang Rui <rui.zhang@...el.com>
> 
> If a device has _PR3._ON, it means the device supports D3_HOT.
> If a device has _PR3._OFF, it means the device supports D3_COLD.
> Add the ability to validate and enter D3_COLD state in ACPI.
> 
> Signed-off-by: Zhang Rui <rui.zhang@...el.com>

This is supposed to be ACPI 5.0 support, right?

So can anyone please tell me what part of the ACPI 5.0 spec is the
basis of this patch, because I can't see that immediately?

The only places where D3Cold is _mentioned_ are Section 7.2.12 (_PRE, which
appears to be new in 5.0), Section 7.2.20 (_S0W), Section 7.2.21 (_S1W),
Section 7.2.22 (_S2W), Section 7.2.23 (_S3W) and Section 7.2.24 (_S4W).
None of them mentions those _PR3._ON and _PR3._OFF things above.

Moreover, my understanding of the spec is that D3Cold means all of the
power resources returned by _PR3 are "off" (whereas some of them will be
"on" in D3hot).

> ---
>  drivers/acpi/power.c |    4 ++--
>  drivers/acpi/scan.c  |   10 +++++++++-
>  2 files changed, 11 insertions(+), 3 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..a9d4391 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -881,8 +881,16 @@ static int acpi_bus_get_power_flags(struct acpi_device *device)
>  
>  			device->power.flags.power_resources = 1;
>  			ps->flags.valid = 1;
> -			for (j = 0; j < ps->resources.count; j++)
> +			for (j = 0; j < ps->resources.count; j++) {
>  				acpi_bus_add_power_resource(ps->resources.handles[j]);
> +				/* Check for D3_COLD support. _PR3._OFF equals D3_COLD ? */
> +				if (i == ACPI_STATE_D3) {
> +					if (j == 0)
> +						device->power.states[ACPI_STATE_D3_COLD].flags.valid = 1;
> +					status = acpi_get_handle(ps->resources.handles[j], "_OFF",  &handle);
> +					device->power.states[ACPI_STATE_D3_COLD].flags.valid &= ACPI_SUCCESS(status);
> +				}
> +			}

Sorry, but this doesn't make sense to me.  Power resources always have
the _OFF method, right?

>  		}
>  
>  		/* Evaluate "_PSx" to see if we can do explicit sets */
> 

Rafael
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