platform/chrome: cros_ec: Query EC protocol version if EC transitions between RO/RW

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@chromium.org>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>

drivers/platform/chrome/cros_ec.c

@@ -138,6 +138,24 @@ 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.
@@ -237,6 +255,18 @@ 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;

include/linux/platform_data/cros_ec_proto.h

@@ -125,6 +125,9 @@ struct cros_ec_command {
  * @host_event_wake_mask: Mask of host events that cause wake from suspend.
  * @last_event_time: exact time from the hard irq when we got notified of
  *     a new event.
+ * @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
@@ -166,6 +169,7 @@ struct cros_ec_device {
 	u32 host_event_wake_mask;
 	u32 last_resume_result;
 	ktime_t last_event_time;
+	struct notifier_block notifier_ready;
 
 	/* The platform devices used by the mfd driver */
 	struct platform_device *ec;