Re: [PATCH v6] platform/chrome: cros_ec: Query EC protocol version if EC transitions between RO/RW

[Gwendal Grignou]

Reviewed-by: Gwendal Grignou <gwendal@xxxxxxxxxxxx>

On Mon, Feb 3, 2020 at 11:30 PM Marek Szyprowski
<m.szyprowski@xxxxxxxxxxx> wrote:
>
> Hi
>
> On 03.02.2020 23:53, Yicheng Li wrote:
> > RO and RW of EC may have different EC protocol version. If EC transitions
> > between RO and RW, but AP does not reboot (this is true for fingerprint
> > microcontroller / cros_fp, but not true for main ec / cros_ec), the AP
> > still uses the protocol version queried before transition, which can
> > cause problems. In the case of fingerprint microcontroller, this causes
> > AP to send the wrong version of EC_CMD_GET_NEXT_EVENT to RO in the
> > interrupt handler, which in turn prevents RO to clear the interrupt
> > line to AP, in an infinite loop.
> >
> > Once an EC_HOST_EVENT_INTERFACE_READY is received, we know that there
> > might have been a transition between RO and RW, so re-query the protocol.
> >
> > Signed-off-by: Yicheng Li <yichengli@xxxxxxxxxxxx>
>
> Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
>
> Works fine on Samsung Exynos-based Chromebooks: Snow, Peach-Pit and
> Peach-Pi.
>
> > ---
> > Hi Enric and Marek,
> >
> >> This patch landed recently in linux-next as commit
> >> 241a69ae8ea8e2defec751fe55dac1287aa044b8. Sadly, it causes following
> >> kernel oops on any key press on Samsung Exynos-based Chromebooks (Snow,
> >> Peach-Pit and Peach-Pi):
> >
> >> Many thanks for report the issue, we will take a look ASAP and revert
> >> this commit meanwhile.
> >
> >> Simply removing the BUG_ON() from cros_ec_get_host_event() function
> >> fixes the issue, but I don't know the protocol details to judge if this
> >> is the correct way of fixing it.
> > The issue was those Samsung Chromebooks (Snow, Peach-Pit and Peach-Pi)
> > do not support mkbp events, yet we applied the same thing to them, which
> > we shouldn't. This v6 should fix it: I Just added a check
> >
> >       if (ec_dev->mkbp_event_supported)
> >
> > in cros_ec_register().
> >
> >
> >
> > drivers/platform/chrome/cros_ec.c           | 29 +++++++++++++++++++++
> >   include/linux/platform_data/cros_ec_proto.h |  3 +++
> >   2 files changed, 32 insertions(+)
> >
> > diff --git a/drivers/platform/chrome/cros_ec.c b/drivers/platform/chrome/cros_ec.c
> > index 9b2d07422e17..f16804db805b 100644
> > --- a/drivers/platform/chrome/cros_ec.c
> > +++ b/drivers/platform/chrome/cros_ec.c
> > @@ -104,6 +104,23 @@ static int cros_ec_sleep_event(struct cros_ec_device *ec_dev, u8 sleep_event)
> >       return ret;
> >   }
> >
> > +static int cros_ec_ready_event(struct notifier_block *nb,
> > +     unsigned long queued_during_suspend, void *_notify)
> > +{
> > +     struct cros_ec_device *ec_dev = container_of(nb, struct cros_ec_device,
> > +                                                  notifier_ready);
> > +     u32 host_event = cros_ec_get_host_event(ec_dev);
> > +
> > +     if (host_event & EC_HOST_EVENT_MASK(EC_HOST_EVENT_INTERFACE_READY)) {
> > +             mutex_lock(&ec_dev->lock);
> > +             cros_ec_query_all(ec_dev);
> > +             mutex_unlock(&ec_dev->lock);
> > +             return NOTIFY_OK;
> > +     }
> > +
> > +     return NOTIFY_DONE;
> > +}
> > +
> >   /**
> >    * cros_ec_register() - Register a new ChromeOS EC, using the provided info.
> >    * @ec_dev: Device to register.
> > @@ -201,6 +218,18 @@ int cros_ec_register(struct cros_ec_device *ec_dev)
> >               dev_dbg(ec_dev->dev, "Error %d clearing sleep event to ec",
> >                       err);
> >
> > +     if (ec_dev->mkbp_event_supported) {
> > +             /*
> > +              * Register the notifier for EC_HOST_EVENT_INTERFACE_READY
> > +              * event.
> > +              */
> > +             ec_dev->notifier_ready.notifier_call = cros_ec_ready_event;
> > +             err = blocking_notifier_chain_register(
> > +                     &ec_dev->event_notifier, &ec_dev->notifier_ready);
> > +             if (err)
> > +                     return err;
> > +     }
> > +
> >       dev_info(dev, "Chrome EC device registered\n");
> >
> >       return 0;
> > diff --git a/include/linux/platform_data/cros_ec_proto.h b/include/linux/platform_data/cros_ec_proto.h
> > index 0d4e4aaed37a..a1c545c464e7 100644
> > --- a/include/linux/platform_data/cros_ec_proto.h
> > +++ b/include/linux/platform_data/cros_ec_proto.h
> > @@ -121,6 +121,8 @@ struct cros_ec_command {
> >    * @event_data: Raw payload transferred with the MKBP event.
> >    * @event_size: Size in bytes of the event data.
> >    * @host_event_wake_mask: Mask of host events that cause wake from suspend.
> > + * @notifier_ready: The notifier_block to let the kernel re-query EC
> > + *      communication protocol when the EC sends EC_HOST_EVENT_INTERFACE_READY.
> >    * @ec: The platform_device used by the mfd driver to interface with the
> >    *      main EC.
> >    * @pd: The platform_device used by the mfd driver to interface with the
> > @@ -161,6 +163,7 @@ struct cros_ec_device {
> >       int event_size;
> >       u32 host_event_wake_mask;
> >       u32 last_resume_result;
> > +     struct notifier_block notifier_ready;
> >
> >       /* The platform devices used by the mfd driver */
> >       struct platform_device *ec;
>
> Best regards
> --
> Marek Szyprowski, PhD
> Samsung R&D Institute Poland
>