Re: [PATCH v4] mfd / platform: cros_ec: Query EC protocol version if EC transitions between RO/RW

From: Enric Balletbo i Serra
Date: Tue Nov 26 2019 - 04:56:47 EST


Hi Yicheng,

I looked at this patch deeply and I have a question.

On 25/11/19 23:15, 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>
> ---
> drivers/platform/chrome/cros_ec.c | 24 +++++++++++++++++++++
> include/linux/platform_data/cros_ec_proto.h | 3 +++
> 2 files changed, 27 insertions(+)
>
> diff --git a/drivers/platform/chrome/cros_ec.c b/drivers/platform/chrome/cros_ec.c
> index 9b2d07422e17..38ec1fb409a5 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);

I am wondering if instead of calling cros_ec_query_all we can just set the proto
version to unknown:

ec_dev->proto_version == EC_PROTO_VERSION_UNKNOWN

and let the cros_ec_cmd_xfer function do its magic.

Should that work?

Thanks,
Enric

> + 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 +218,13 @@ int cros_ec_register(struct cros_ec_device *ec_dev)
> dev_dbg(ec_dev->dev, "Error %d clearing sleep event to ec",
> err);
>
> + /* 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;
>