[PATCH] platform/chrome: cros_ec_rpmsg: record last_event_time on host event

[Cheng Yueh <cyueh@google.com>]

Transports with a dedicated interrupt line (ec_dev->irq > 0, such as SPI
and I2C) record ec_dev->last_event_time in the top-half
cros_ec_irq_handler(), while transports without one (ec_dev->irq == 0,
such as LPC in cros_ec_lpc_acpi_notify() and ISHTP in ish_event_cb())
record it in their respective event callbacks.

cros_ec_rpmsg also operates with ec_dev->irq == 0: when an MKBP event
notification (HOST_EVENT_MARK) arrives in cros_ec_rpmsg_callback(), it
schedules host_event_work to invoke the bottom-half cros_ec_irq_thread()
directly, bypassing cros_ec_irq_handler() and leaving
ec_dev->last_event_time as 0.

cros_ec_sensorhub_ring relies on ec_dev->last_event_time (via
fifo_timestamp) as the AP CLOCK_BOOTTIME reference timestamp to calibrate
the offset and clock drift between the remote processor's local hardware
timer and the AP timebase. Without this calibration, IIO sensor sample
timestamps cannot be synchronized to CLOCK_BOOTTIME
(SystemClock.elapsedRealtimeNanos()), failing the Android CTS sensor
specification TimestampClockSourceVerification.

Record ec_dev->last_event_time = cros_ec_get_time_ns() upon receiving
HOST_EVENT_MARK in cros_ec_rpmsg_callback(), matching the other ChromeOS
EC transport drivers.

Fixes: 2de89fd98958 ("platform/chrome: cros_ec: Add EC host command support using rpmsg")
Signed-off-by: Cheng Yueh <cyueh@google.com>
---
 drivers/platform/chrome/cros_ec_rpmsg.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/platform/chrome/cros_ec_rpmsg.c b/drivers/platform/chrome/cros_ec_rpmsg.c
index 39d3b50a7c09..07b9e71ac8e3 100644
--- a/drivers/platform/chrome/cros_ec_rpmsg.c
+++ b/drivers/platform/chrome/cros_ec_rpmsg.c
@@ -180,6 +180,7 @@ 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) {
+		ec_dev->last_event_time = cros_ec_get_time_ns();
 		/*
 		 * If the host event is sent before cros_ec_register is
 		 * finished, queue the host event.
-- 
2.56.0.385.gac671c819a-goog