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

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Date:	Wed, 9 Dec 2015 09:18:29 +0800
From:	Ken Xue <ken.xue@....com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
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 Tue, 2015-12-08 at 14:14 +0100, Rafael J. Wysocki wrote:
> On Tuesday, December 08, 2015 09:37:56 AM Ken Xue wrote:
> > On Mon, 2015-12-07 at 23:48 +0100, Rafael J. Wysocki wrote:
> > > 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?
> > 
> > My problem is that
> > "acpi_device_can_poweroff" is called by "zpodd_init" in libata-zpodd.c. 
> > And ZPODD feature only can be enabled when D3_COLD is valid.
> 
> This means that acpi_device_can_poweroff() needs to be updated.  What about
> like this:
> 
> static inline bool acpi_device_can_poweroff(struct acpi_device *adev)
> {
> 	return adev->power.states[ACPI_STATE_D3_COLD].flags.valid ||
		((acpi_gbl_FADT.header.revision < 6) &&
> 		 adev->power.states[ACPI_STATE_D3_HOT].flags.explicit_set);
> }

It also could work by refining "acpi_device_can_poweroff".
But ZPODD exactly requests D3 Cold support, So, checking ACPI version
should be necessary when D3 hot is explicit_set.
If you do not have other concern, I will submit new Patch later.


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