linux-kernel - Re: [PATCH 1/1] ACPI: Support D3 COLD device for old BIOS

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Date:	Mon, 07 Dec 2015 23:48:56 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Ken Xue <ken.xue@....com>
Cc:	lenb@...nel.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, SPG_Linux_Kernel@....com,
	mika.westerberg@...ux.intel.com,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	Ivan.Zheng@....com, Alex.Chuang@....com
Subject: Re: [PATCH 1/1] ACPI: Support D3 COLD device for old BIOS

On Monday, December 07, 2015 12:44:33 PM Ken Xue wrote:
> D3cold is only regarded as valid if the "_PR3" object is present
> for the given device after the commit <20dacb71ad28>
> (ACPI/PM: Reworkdevice power management to follow ACPI 6).
> 
> But some old BIOS only defined "_PS3" for the D3COLD device.
> And old kernel also believes the device has "_PS3" is a
> D3COLD device.
> 
> So, add some logics for supporting D3 COLD device for old BIOS
> which is compatible with earlier ACPI spec.
> 
> Signed-off-by: Ken Xue <Ken.Xue@....com>
> Reported-and-tested-by: Gang Long <Gang.Long@....com>

Well, what really is the problem?

acpi_device_set_power() has a special case specifically for D3cold and
falls back to D3hot if D3cold has been requested but is not "valid".

> ---
>  drivers/acpi/scan.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 01136b8..85c16bb 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -979,7 +979,9 @@ static void acpi_bus_get_power_flags(struct acpi_device *device)
>  		acpi_bus_init_power_state(device, i);
>  
>  	INIT_LIST_HEAD(&device->power.states[ACPI_STATE_D3_COLD].resources);
> -	if (!list_empty(&device->power.states[ACPI_STATE_D3_HOT].resources))
> +	if (!list_empty(&device->power.states[ACPI_STATE_D3_HOT].resources) ||
> +		((acpi_gbl_FADT.header.revision < 6) &&
> +		device->power.states[ACPI_STATE_D3_HOT].flags.explicit_set))
>  		device->power.states[ACPI_STATE_D3_COLD].flags.valid = 1;
>  
>  	/* Set defaults for D0 and D3hot states (always valid) */
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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