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

[Yicheng Li]

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>
---
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;
-- 
2.24.1