linux-kernel - Re: [PATCH] usb: phy: am335x: Enable USB remote wakeup using PHY wakeup

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Message-ID: <20131218163329.GH4970@saruman.home>
Date:	Wed, 18 Dec 2013 10:33:29 -0600
From:	Felipe Balbi <balbi@...com>
To:	George Cherian <george.cherian@...com>,
	Alan Stern <stern@...land.harvard.edu>
CC:	<linux-usb@...r.kernel.org>, <balbi@...com>,
	<gregkh@...uxfoundation.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: phy: am335x: Enable USB remote wakeup using PHY
 wakeup

Hi,

On Wed, Dec 18, 2013 at 06:52:09PM +0530, George Cherian wrote:
> USB remote wakeup using PHY wakeup is supported only in standby mode.
> Enabling the PHY_WKUP will break DS0 mode of system suspend.
> If the same is enabled while entering DS0, AM33xx never stays in DS0,
> it returns immediately from DS0. By default make the PHY wakeup
> disabled, using sysfs entry enable the same manually to get
> the remote wakeup working from standby.
> 
> echo enabled > /sys/bus/platform/device/<usb phy id>/power/wakeup
> This will enable the PHY wakeup while going to standby.
> 
> PHY wakeup feature is required to wakeup  the system from standby
> state. Since AM33xx has a bug in which PHY wakeup should not
> be enabled while entering DS0, disable the same by default.
> A user wishing to use USB wakeup from standby mode need to enable
> the same using the sysfs entries.
> 
> Also remove am335x_phy_runtime_(suspend/resume) this driver doesnot really
> enable/disable the clocks to the PHY.
> Add am335x_phy_(suspend/resume) and use the same for enabling the PHY_WKUP.
> 
> Signed-off-by: George Cherian <george.cherian@...com>
> ---
>  drivers/usb/phy/phy-am335x.c | 46 +++++++++++++++++++++++++++++++++-----------
>  1 file changed, 35 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/usb/phy/phy-am335x.c b/drivers/usb/phy/phy-am335x.c
> index 6370e50..3f78eaf 100644
> --- a/drivers/usb/phy/phy-am335x.c
> +++ b/drivers/usb/phy/phy-am335x.c
> @@ -64,6 +64,19 @@ static int am335x_phy_probe(struct platform_device *pdev)
>  	am_phy->usb_phy_gen.phy.shutdown = am335x_shutdown;
>  
>  	platform_set_drvdata(pdev, am_phy);
> +	device_init_wakeup(dev, true);
> +
> +	/*
> +	 * If we leave PHY wakeup enabled then AM33XX wakes up
> +	 * immediately from DS0. To avoid this we mark dev->power.can_wakeup
> +	 * to false. The same is checked in suspend routine to decide
> +	 * on whether to enable PHY wakeup or not.
> +	 * PHY wakeup works fine in standby mode, there by allowing us to
> +	 * handle remote wakeup, wakeup on disconnect and connect.
> +	 */
> +
> +	device_set_wakeup_enable(dev, false);
> +	phy_ctrl_power(am_phy->phy_ctrl, am_phy->id, false);
>  
>  	return 0;
>  
> @@ -78,40 +91,51 @@ static int am335x_phy_remove(struct platform_device *pdev)
>  	return 0;
>  }
>  
> -#ifdef CONFIG_PM_RUNTIME
> -
> -static int am335x_phy_runtime_suspend(struct device *dev)
> +#ifdef CONFIG_PM_SLEEP
> +static int am335x_phy_suspend(struct device *dev)
>  {
>  	struct platform_device	*pdev = to_platform_device(dev);
>  	struct am335x_phy *am_phy = platform_get_drvdata(pdev);
>  
> +	/*
> +	 * Enable phy wakeup only if dev->power.can_wakeup is true.
> +	 * Make sure to enable wakeup to support remote wakeup	in
> +	 * standby mode ( same is not supported in OFF(DS0) mode).
> +	 * Enable it by doing
> +	 * echo enabled > /sys/bus/platform/devices/<usb-phy-id>/power/wakeup
> +	 */

Alan, any suggestions on how to handle wakeup correctly ? I mean, it
should be enabled by default during runtime PM and disabled during
system sleep. But when it comes to default state of can_wakeup field,
what should we do ? Should the driver be fiddling with that ? Leave it
to the bus driver ? Any tips ?

cheers

-- 
balbi

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