linux-kernel - Re: [PATCH RESEND] phy: phy-twl4030-usb: fix denied runtime access

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Date:   Mon, 17 Sep 2018 10:51:31 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Andreas Kemnade <andreas@...nade.info>
Cc:     kishon@...com, lee.jones@...aro.org, daniel.thompson@...aro.org,
        wsa@...-dreams.de, linux-omap@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>
Subject: Re: [PATCH RESEND] phy: phy-twl4030-usb: fix denied runtime access

Hi Andreas,

On Mon, Sep 17, 2018 at 07:22:54AM +0200, Andreas Kemnade wrote:
> When runtime is not enabled, pm_runtime_get_sync() returns -EACCESS,
> the counter will be incremented but the resume callback not called,
> so enumeration and charging will not start properly.
> To avoid that happen, wait and try again later.
> 
> Practically this happens when the device is woken up from suspend by
> plugging in usb.
> 
> Signed-off-by: Andreas Kemnade <andreas@...nade.info>
> ---
>  drivers/phy/ti/phy-twl4030-usb.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/phy/ti/phy-twl4030-usb.c b/drivers/phy/ti/phy-twl4030-usb.c
> index a44680d64f9b..1f3cf4e48383 100644
> --- a/drivers/phy/ti/phy-twl4030-usb.c
> +++ b/drivers/phy/ti/phy-twl4030-usb.c
> @@ -552,6 +552,15 @@ static irqreturn_t twl4030_usb_irq(int irq, void *_twl)
>  
>  	status = twl4030_usb_linkstat(twl);
>  
> +	/* we might get here too early when runtime is not ready yet
> +	 * and we will get an EACCESS later, so try again later
> +	 */

How exactly can this happen? What disables (and later re-enables)
runtime PM? How can we guarantee that the interrupt will be
re-triggered?

> +	if (!pm_runtime_enabled(twl->dev)) {
> +		cancel_delayed_work(&twl->id_workaround_work);
> +		schedule_delayed_work(&twl->id_workaround_work, HZ);
> +		return IRQ_HANDLED;
> +	}
> +
>  	mutex_lock(&twl->lock);
>  	if (status >= 0 && status != twl->linkstat) {
>  		status_changed =
> -- 
> 2.11.0
> 

Thanks.

-- 
Dmitry