linux-kernel - Re: [PATCH] ACPI: PM: Fix regression in acpi_device_set

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Message-Id: <27715F95-E729-4EF5-B2BA-03BA3C87AE29@canonical.com>
Date:   Thu, 1 Aug 2019 14:11:00 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux ACPI <linux-acpi@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Mario Limonciello <mario.limonciello@...l.com>
Subject: Re: [PATCH] ACPI: PM: Fix regression in acpi_device_set_power()

at 07:31, Rafael J. Wysocki <rjw@...ysocki.net> wrote:

> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> Commit f850a48a0799 ("ACPI: PM: Allow transitions to D0 to occur in
> special cases") overlooked the fact that acpi_power_transition() may
> change the power.state value for the target device and if that
> happens, it may confuse acpi_device_set_power() and cause it to
> omit the _PS0 evaluation which on some systems is necessary to
> change power states of devices from low-power to D0.
>
> Fix that by saving the current value of power.state for the
> target device before passing it to acpi_power_transition() and
> using the saved value in a subsequent check.
>
> Fixes: f850a48a0799 ("ACPI: PM: Allow transitions to D0 to occur in  
> special cases")
> Reported-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> Reported-by: Mario Limonciello <mario.limonciello@...l.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Tested-by: Kai-Heng Feng <kai.heng.feng@...onical.com>

> ---
>  drivers/acpi/device_pm.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> Index: linux-pm/drivers/acpi/device_pm.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/device_pm.c
> +++ linux-pm/drivers/acpi/device_pm.c
> @@ -236,13 +236,15 @@ int acpi_device_set_power(struct acpi_de
>  		if (device->power.flags.power_resources)
>  			result = acpi_power_transition(device, target_state);
>  	} else {
> +		int cur_state = device->power.state;
> +
>  		if (device->power.flags.power_resources) {
>  			result = acpi_power_transition(device, ACPI_STATE_D0);
>  			if (result)
>  				goto end;
>  		}
>
> -		if (device->power.state == ACPI_STATE_D0) {
> +		if (cur_state == ACPI_STATE_D0) {
>  			int psc;
>
>  			/* Nothing to do here if _PSC is not present. */