linux-kernel - Re: [PATCH 1/4] usb: phy: twl4030: make runtime pm more reliable.

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Date:	Tue, 24 Feb 2015 12:44:11 -0800
From:	Tony Lindgren <tony@...mide.com>
To:	NeilBrown <neilb@...e.de>
Cc:	Felipe Balbi <balbi@...com>,
	Kishon Vijay Abraham I <kishon@...com>,
	linux-omap@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
	GTA04 owners <gta04-owner@...delico.com>
Subject: Re: [PATCH 1/4] usb: phy: twl4030: make runtime pm more reliable.

* NeilBrown <neilb@...e.de> [150223 19:45]:
> A construct like:
> 
>         if (pm_runtime_suspended(twl->dev))
>                pm_runtime_get_sync(twl->dev);
> 
> is against the spirit of the runtime_pm interface as it
> makes the internal refcounting useless.
> 
> In this case it is also racy, particularly as 'put_autosuspend'
> is use to drop a reference.
> When that happens a timer is started and the device is
> runtime-suspended after the timeout.
> If the above code runs in this window, the device will not be
> found to be suspended so no pm_runtime reference is taken.
> When the timer expires the device will be suspended, which is
> against the intention of the code.
> 
> So be more direct is taking and dropping references.
> If twl->linkstat is VBUS_VALID or ID_GROUND, then hold a
> pm_runtime reference, otherwise don't.

Looks good to me, thanks for fixing it. I've tested this series
on beagleboard-xm by plugging and unplugging devices and
switching between host and peripheral mode, things still
idle properly for off-idle. So please feel free to add:

Tested-by: Tony Lindgren <tony@...mide.com>
 
> Signed-off-by: NeilBrown <neilb@...e.de>
> ---
>  drivers/phy/phy-twl4030-usb.c |   20 +++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/phy/phy-twl4030-usb.c b/drivers/phy/phy-twl4030-usb.c
> index 8e87f54671f3..97c59074233f 100644
> --- a/drivers/phy/phy-twl4030-usb.c
> +++ b/drivers/phy/phy-twl4030-usb.c
> @@ -536,8 +536,13 @@ static irqreturn_t twl4030_usb_irq(int irq, void *_twl)
>  
>  	mutex_lock(&twl->lock);
>  	if (status >= 0 && status != twl->linkstat) {
> +		status_changed =
> +			(twl->linkstat == OMAP_MUSB_VBUS_VALID ||
> +			 twl->linkstat == OMAP_MUSB_ID_GROUND)
> +			!=
> +			(status == OMAP_MUSB_VBUS_VALID ||
> +			 status == OMAP_MUSB_ID_GROUND);
>  		twl->linkstat = status;
> -		status_changed = true;
>  	}
>  	mutex_unlock(&twl->lock);
>  
> @@ -555,13 +560,10 @@ static irqreturn_t twl4030_usb_irq(int irq, void *_twl)
>  		 */
>  		if ((status == OMAP_MUSB_VBUS_VALID) ||
>  		    (status == OMAP_MUSB_ID_GROUND)) {
> -			if (pm_runtime_suspended(twl->dev))
> -				pm_runtime_get_sync(twl->dev);
> +			pm_runtime_get_sync(twl->dev);
>  		} else {
> -			if (pm_runtime_active(twl->dev)) {
> -				pm_runtime_mark_last_busy(twl->dev);
> -				pm_runtime_put_autosuspend(twl->dev);
> -			}
> +			pm_runtime_mark_last_busy(twl->dev);
> +			pm_runtime_put_autosuspend(twl->dev);
>  		}
>  		omap_musb_mailbox(status);
>  	}
> @@ -768,6 +770,10 @@ static int twl4030_usb_remove(struct platform_device *pdev)
>  
>  	/* disable complete OTG block */
>  	twl4030_usb_clear_bits(twl, POWER_CTRL, POWER_CTRL_OTG_ENAB);
> +
> +	if (twl->linkstat == OMAP_MUSB_VBUS_VALID ||
> +	    twl->linkstat == OMAP_MUSB_ID_GROUND)
> +		pm_runtime_put_noidle(twl->dev);
>  	pm_runtime_mark_last_busy(twl->dev);
>  	pm_runtime_put(twl->dev);
>  
> 
> 
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