linux-kernel - Re: [char-misc-next] mei: me: allow runtime pm for platform with D0i3

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Date:   Wed, 3 Jan 2018 13:26:22 +0100
From:   "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
To:     Tomas Winkler <tomas.winkler@...el.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alexander Usyskin <alexander.usyskin@...el.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [char-misc-next] mei: me: allow runtime pm for platform with D0i3

On 1/2/2018 11:01 AM, Tomas Winkler wrote:
>  From the pci power documentation:
> "The driver itself should not call pm_runtime_allow(), though. Instead,
> it should let user space or some platform-specific code do that (user space
> can do it via sysfs as stated above)..."
>
> However, the S0ix residency cannot be reached without MEI device getting
> into low power state. Hence, for mei devices that support D0i3, it's better
> to make runtime power management mandatory and not rely on the system
> integration such as udev rules.

It still is not mandatory with this change.  The default changes from 
"on" to "auto", but still user space can change it back to "on".

The change itself look OK, though.

> This policy cannot be applied globally as some older platforms
> were found to have broken power management.
>
> Cc: <stable@...r.kernel.org> v4.13+
> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Signed-off-by: Tomas Winkler <tomas.winkler@...el.com>
> Reviewed-by: Alexander Usyskin <alexander.usyskin@...el.com>
> ---
>   drivers/misc/mei/pci-me.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/misc/mei/pci-me.c b/drivers/misc/mei/pci-me.c
> index f4f17552c9b8..4a0ccda4d04b 100644
> --- a/drivers/misc/mei/pci-me.c
> +++ b/drivers/misc/mei/pci-me.c
> @@ -238,8 +238,11 @@ static int mei_me_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>   	 */
>   	mei_me_set_pm_domain(dev);
>   
> -	if (mei_pg_is_enabled(dev))
> +	if (mei_pg_is_enabled(dev)) {
>   		pm_runtime_put_noidle(&pdev->dev);
> +		if (hw->d0i3_supported)
> +			pm_runtime_allow(&pdev->dev);
> +	}
>   
>   	dev_dbg(&pdev->dev, "initialization successful.\n");
>