Re: [PATCH v4 04/17] platform: chrome: cros-ec: record event timestamp in the hard irq

Jonathan Cameron
2019-11-10T12:31:06Z

On Tue, 5 Nov 2019 14:26:39 -0800
Gwendal Grignou <gwendal@chromium.org> wrote:

> 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>
A minor issue with kernel-doc (I think...)

Otherwise,
Acked-by: Jonathan Cameron <Jonathan.Cameron@kernel.org>
> ---
> Changes in v4:
> Check patch with --strict option
> Alignement
> No changes in v3.
> Changes in v2:
> Make cros_ec_get_time_ns inline.
> Using ktime_t instead of s64 when dealing with time.
> Added code in ishtp to gather timestamp.
>
> drivers/platform/chrome/cros_ec.c | 17 ++++++++++++++---
> drivers/platform/chrome/cros_ec_ishtp.c | 17 +++++++++++++++--
> drivers/platform/chrome/cros_ec_lpc.c | 2 ++
> include/linux/platform_data/cros_ec_proto.h | 16 ++++++++++++++++
> 4 files changed, 47 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 @@ static void process_recv(struct ishtp_cl *cros_ish_cl,
> 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,
> diff --git a/include/linux/platform_data/cros_ec_proto.h b/include/linux/platform_data/cros_ec_proto.h
> index 691f9e953a96..b183024fef1f 100644
> --- a/include/linux/platform_data/cros_ec_proto.h
> +++ b/include/linux/platform_data/cros_ec_proto.h
> @@ -122,6 +122,8 @@ 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.
> + * @last_event_time: exact time from the hard irq when we got notified of
> + * a new event.
> * @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
> @@ -162,6 +164,7 @@ struct cros_ec_device {
> int event_size;
> u32 host_event_wake_mask;
> u32 last_resume_result;
> + ktime_t last_event_time;
>
> /* The platform devices used by the mfd driver */
> struct platform_device *ec;
> @@ -210,4 +213,17 @@ int cros_ec_check_features(struct cros_ec_dev *ec, int feature);
>
> int cros_ec_get_sensor_count(struct cros_ec_dev *ec);
>
> +/**
> + * cros_ec_get_time_ns - Return time in ns.

Fairly sure that's not correct kernel-doc. Please run
../scripts/kernel-doc over the files and fix the warnings.

* cros_ec_get_time_ns() - Return time in ns.

> + *
> + * This is the function used to record the time for last_event_time in struct
> + * cros_ec_device during the hard irq.
> + *
> + * Return: ktime_t format since boot.
> + */
> +static inline ktime_t cros_ec_get_time_ns(void)
> +{
> + return ktime_get_boottime_ns();
> +}
> +
> #endif /* __LINUX_CROS_EC_PROTO_H */