linux-kernel - Re: [PATCH] platform/chrome: cros_ec

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Date:   Sat, 15 Feb 2020 11:56:48 +0800
From:   Pi-Hsun Shih <pihsun@...omium.org>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] platform/chrome: cros_ec_rpmsg: Fix race with host event.

Hi Enric,

On Fri, Feb 14, 2020 at 11:10 PM Enric Balletbo i Serra
<enric.balletbo@...labora.com> wrote:
>
> Hi Pi-Hsun,
>
> On 14/2/20 9:26, Pi-Hsun Shih wrote:
> > Host event can be sent by remoteproc by any time, and
> > cros_ec_rpmsg_callback would be called after cros_ec_rpmsg_create_ept.
> > But the cros_ec_device is initialized after that, which cause host event
> > handler to use cros_ec_device that are not initialized properly yet.
> >
>
> I don't have the hardware to test but, can't we call first cros_ec_register and
> then cros_ec_rpmsg_create_ept?
>
> Start receiving driver callbacks before finishing to probe the drivers itself
> sounds weird to me.
>
> Thanks,
>  Enric

Since cros_ec_register calls cros_ec_query_all, which sends message to
remoteproc using cros_ec_pkt_xfer_rpmsg (to query protocol version),
the ec_rpmsg->ept need to be ready before calling cros_ec_register.

>
> > Fix this by don't schedule host event handler before cros_ec_register
> > returns. Instead, remember that we have a pending host event, and
> > schedule host event handler after cros_ec_register.
> >
> > Fixes: 71cddb7097e2 ("platform/chrome: cros_ec_rpmsg: Fix race with host command when probe failed.")
> > Signed-off-by: Pi-Hsun Shih <pihsun@...omium.org>
> > ---
> >  drivers/platform/chrome/cros_ec_rpmsg.c | 16 +++++++++++++++-
> >  1 file changed, 15 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/platform/chrome/cros_ec_rpmsg.c b/drivers/platform/chrome/cros_ec_rpmsg.c
> > index dbc3f5523b83..7e8629e3db74 100644
> > --- a/drivers/platform/chrome/cros_ec_rpmsg.c
> > +++ b/drivers/platform/chrome/cros_ec_rpmsg.c
> > @@ -44,6 +44,8 @@ struct cros_ec_rpmsg {
> >       struct completion xfer_ack;
> >       struct work_struct host_event_work;
> >       struct rpmsg_endpoint *ept;
> > +     bool has_pending_host_event;
> > +     bool probe_done;
> >  };
> >
> >  /**
> > @@ -177,7 +179,14 @@ static int cros_ec_rpmsg_callback(struct rpmsg_device *rpdev, void *data,
> >               memcpy(ec_dev->din, resp->data, len);
> >               complete(&ec_rpmsg->xfer_ack);
> >       } else if (resp->type == HOST_EVENT_MARK) {
> > -             schedule_work(&ec_rpmsg->host_event_work);
> > +             /*
> > +              * If the host event is sent before cros_ec_register is
> > +              * finished, queue the host event.
> > +              */
> > +             if (ec_rpmsg->probe_done)
> > +                     schedule_work(&ec_rpmsg->host_event_work);
> > +             else
> > +                     ec_rpmsg->has_pending_host_event = true;
> >       } else {
> >               dev_warn(ec_dev->dev, "rpmsg received invalid type = %d",
> >                        resp->type);
> > @@ -240,6 +249,11 @@ static int cros_ec_rpmsg_probe(struct rpmsg_device *rpdev)
> >               return ret;
> >       }
> >
> > +     ec_rpmsg->probe_done = true;
> > +
> > +     if (ec_rpmsg->has_pending_host_event)
> > +             schedule_work(&ec_rpmsg->host_event_work);
> > +
> >       return 0;
> >  }
> >
> >
> > base-commit: b19e8c68470385dd2c5440876591fddb02c8c402
> >