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Date:   Mon, 17 Sep 2018 20:56:34 +0200
From:   Andreas Kemnade <andreas@kemnade.info>
To:     Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc:     kishon@ti.com, lee.jones@linaro.org, daniel.thompson@linaro.org,
        wsa@the-dreams.de, linux-omap@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Discussions about the Letux Kernel 
        <letux-kernel@openphoenux.org>
Subject: Re: [PATCH RESEND] phy: phy-twl4030-usb: fix denied runtime access
Message-ID: <20180917205634.6a320cad@aktux>
In-Reply-To: <20180917175131.GA104770@dtor-ws>
References: <20180917052254.12336-1-andreas@kemnade.info>
        <20180917175131.GA104770@dtor-ws>
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Hi Dmitry,

On Mon, 17 Sep 2018 10:51:31 -0700
Dmitry Torokhov <dmitry.torokhov@gmail.com> wrote:

> Hi Andreas,
>=20
> 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.
> >=20
> > Practically this happens when the device is woken up from suspend by
> > plugging in usb.
> >=20
> > Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
> > ---
> >  drivers/phy/ti/phy-twl4030-usb.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >=20
> > diff --git a/drivers/phy/ti/phy-twl4030-usb.c b/drivers/phy/ti/phy-twl4=
030-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)
> > =20
> >  	status =3D twl4030_usb_linkstat(twl);
> > =20
> > +	/* we might get here too early when runtime is not ready yet
> > +	 * and we will get an EACCESS later, so try again later
> > +	 */ =20
>=20
> How exactly can this happen? What disables (and later re-enables)
> runtime PM?=20
If the whole resume process is started by plugging in usb, the
interrupt will be triggered still in the resume process so that=20
runtime resume is not yet possible, pm_runtime_get_sync() returns
EACCESS

> How can we guarantee that the interrupt will be
> re-triggered?
>=20
The interrupt will not be re-triggered but the handler will be
called at some other places...

> > +	if (!pm_runtime_enabled(twl->dev)) {
> > +		cancel_delayed_work(&twl->id_workaround_work);
> > +		schedule_delayed_work(&twl->id_workaround_work, HZ);
> > +		return IRQ_HANDLED;
> > +	}
> > +
... for example by this delayed work which is already there.

Regards,
Andreas

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