linux-kernel - Re: [PATCH] ACPI / PM: Fix PM initialization for devices that are not present

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Date:	Mon, 5 Jan 2015 15:40:10 +0200
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI / PM: Fix PM initialization for devices that are
 not present

On Thu, Jan 01, 2015 at 11:38:28PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> If an ACPI device object whose _STA returns 0 (not present and not
> functional) has _PR0 or _PS0, its power_manageable flag will be set
> and acpi_bus_init_power() will return 0 for it.  Consequently, if
> such a device object is passed to the ACPI device PM functions, they
> will attempt to carry out the requested operation on the device,
> although they should not do that for devices that are not present.
> 
> To fix that problem make acpi_bus_init_power() return an error code
> for devices that are not present which will cause power_manageable to
> be cleared for them as appropriate in acpi_bus_get_power_flags().
> However, the lists of power resources should not be freed for the
> device in that case, so modify acpi_bus_get_power_flags() to keep
> those lists even if acpi_bus_init_power() returns an error.
> Accordingly, when deciding whether or not the lists of power
> resources need to be freed, acpi_free_power_resources_lists()
> should check the power.flags.power_resources flag instead of
> flags.power_manageable, so make that change too.
> 
> Furthermore, if acpi_bus_attach() sees that flags.initialized is
> unset for the given device, it should reset the power management
> settings of the device and re-initialize them from scratch instead
> of relying on the previous settings (the device may have appeared
> after being not present previously, for example), so make it use
> the 'valid' flag of the D0 power state as the initial value of
> flags.power_manageable for it and call acpi_bus_init_power() to
> discover its current power state.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
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