platform/chrome: cros-ec: Record event timestamp in the hard irq

To improve sensor timestamp precision, given EC and AP are in different
time domains, the AP needs to try to record the exact moment an event
was signalled to the AP by the EC as soon as possible after it happens.

First thing in the hard irq is the best place for this.

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Acked-by: Jonathan Cameron <Jonathan.Cameron@kernel.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>

3 files changed, 31 insertions, 5 deletions

diff --git a/drivers/platform/chrome/cros_ec.c b/drivers/platform/chrome/cros_ec.c
index 9b2d07422e17..925f84dbf621 100644
--- a/drivers/platform/chrome/cros_ec.c
+++ b/drivers/platform/chrome/cros_ec.c
@@ -31,6 +31,15 @@ static struct cros_ec_platform pd_p = {
 	.cmd_offset = EC_CMD_PASSTHRU_OFFSET(CROS_EC_DEV_PD_INDEX),
 };
 
+static irqreturn_t ec_irq_handler(int irq, void *data)
+{
+	struct cros_ec_device *ec_dev = data;
+
+	ec_dev->last_event_time = cros_ec_get_time_ns();
+
+	return IRQ_WAKE_THREAD;
+}
+
 static irqreturn_t ec_irq_thread(int irq, void *data)
 {
 	struct cros_ec_device *ec_dev = data;
@@ -141,9 +150,11 @@ int cros_ec_register(struct cros_ec_device *ec_dev)
 	}
 
 	if (ec_dev->irq) {
-		err = devm_request_threaded_irq(dev, ec_dev->irq, NULL,
-				ec_irq_thread, IRQF_TRIGGER_LOW | IRQF_ONESHOT,
-				"chromeos-ec", ec_dev);
+		err = devm_request_threaded_irq(dev, ec_dev->irq,
+						ec_irq_handler,
+						ec_irq_thread,
+						IRQF_TRIGGER_LOW | IRQF_ONESHOT,
+						"chromeos-ec", ec_dev);
 		if (err) {
 			dev_err(dev, "Failed to request IRQ %d: %d",
 				ec_dev->irq, err);
diff --git a/drivers/platform/chrome/cros_ec_ishtp.c b/drivers/platform/chrome/cros_ec_ishtp.c
index 25ca2c894b4d..5c848f22b44b 100644
--- a/drivers/platform/chrome/cros_ec_ishtp.c
+++ b/drivers/platform/chrome/cros_ec_ishtp.c
@@ -200,13 +200,14 @@ static int ish_send(struct ishtp_cl_data *client_data,
  * process_recv() - Received and parse incoming packet
  * @cros_ish_cl: Client instance to get stats
  * @rb_in_proc: Host interface message buffer
+ * @timestamp: Timestamp of when parent callback started
  *
  * Parse the incoming packet. If it is a response packet then it will
  * update per instance flags and wake up the caller waiting to for the
  * response. If it is an event packet then it will schedule event work.
  */
 static void process_recv(struct ishtp_cl *cros_ish_cl,
-			 struct ishtp_cl_rb *rb_in_proc)
+			 struct ishtp_cl_rb *rb_in_proc, ktime_t timestamp)
 {
 	size_t data_len = rb_in_proc->buf_idx;
 	struct ishtp_cl_data *client_data =
@@ -295,6 +296,11 @@ error_wake_up:
 		break;
 
 	case CROS_MKBP_EVENT:
+		/*
+		 * Set timestamp from beginning of function since we actually
+		 * got an incoming MKBP event
+		 */
+		client_data->ec_dev->last_event_time = timestamp;
 		/* The event system doesn't send any data in buffer */
 		schedule_work(&client_data->work_ec_evt);
 
@@ -322,10 +328,17 @@ static void ish_event_cb(struct ishtp_cl_device *cl_device)
 {
 	struct ishtp_cl_rb *rb_in_proc;
 	struct ishtp_cl	*cros_ish_cl = ishtp_get_drvdata(cl_device);
+	ktime_t timestamp;
+
+	/*
+	 * Take timestamp as close to hardware interrupt as possible for sensor
+	 * timestamps.
+	 */
+	timestamp = cros_ec_get_time_ns();
 
 	while ((rb_in_proc = ishtp_cl_rx_get_rb(cros_ish_cl)) != NULL) {
 		/* Decide what to do with received data */
-		process_recv(cros_ish_cl, rb_in_proc);
+		process_recv(cros_ish_cl, rb_in_proc, timestamp);
 	}
 }
 
diff --git a/drivers/platform/chrome/cros_ec_lpc.c b/drivers/platform/chrome/cros_ec_lpc.c
index 7d10d909435f..3c77496e164d 100644
--- a/drivers/platform/chrome/cros_ec_lpc.c
+++ b/drivers/platform/chrome/cros_ec_lpc.c
@@ -313,6 +313,8 @@ static void cros_ec_lpc_acpi_notify(acpi_handle device, u32 value, void *data)
 {
 	struct cros_ec_device *ec_dev = data;
 
+	ec_dev->last_event_time = cros_ec_get_time_ns();
+
 	if (ec_dev->mkbp_event_supported &&
 	    cros_ec_get_next_event(ec_dev, NULL) > 0)
 		blocking_notifier_call_chain(&ec_dev->event_notifier, 0,