Re: [PATCH 04/13] platform: chrome: cros-ec: record event timestamp in the hard irq

Jonathan Cameron
2019-10-05T15:44:13Z

On Sun, 22 Sep 2019 10:50:12 -0700
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>
If this is only going to be used in IIO paths, the there is a control
to set which clock is used. This is really a legacy thing due to
me once picking a silly default, but we may be causing confusion by
having that control but it having no effect.

Otherwise looks good to me.

> ---
> drivers/platform/chrome/cros_ec.c | 18 +++++++++++++++++-
> drivers/platform/chrome/cros_ec_lpc.c | 2 ++
> include/linux/platform_data/cros_ec_proto.h | 15 +++++++++++++++
> 3 files changed, 34 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/platform/chrome/cros_ec.c b/drivers/platform/chrome/cros_ec.c
> index fd77e6fa74c2..f49eb1d1e3cd 100644
> --- a/drivers/platform/chrome/cros_ec.c
> +++ b/drivers/platform/chrome/cros_ec.c
> @@ -31,6 +31,21 @@ static struct cros_ec_platform pd_p = {
> .cmd_offset = EC_CMD_PASSTHRU_OFFSET(CROS_EC_DEV_PD_INDEX),
> };
>
> +s64 cros_ec_get_time_ns(void)
> +{
> + return ktime_get_boottime_ns();
> +}
> +EXPORT_SYMBOL(cros_ec_get_time_ns);
> +
> +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;
> @@ -132,7 +147,8 @@ int cros_ec_register(struct cros_ec_device *ec_dev)
> }
>
> if (ec_dev->irq) {
> - err = devm_request_threaded_irq(dev, ec_dev->irq, NULL,
> + 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) {
> 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 e91e3fcb0348..ab12e28f2107 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.
> + * @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
> @@ -161,6 +163,7 @@ struct cros_ec_device {
> int event_size;
> u32 host_event_wake_mask;
> u32 last_resume_result;
> + s64 last_event_time;
>
> /* The platform devices used by the mfd driver */
> struct platform_device *ec;
> @@ -308,4 +311,16 @@ int cros_ec_get_next_event(struct cros_ec_device *ec_dev, bool *wake_event);
> */
> u32 cros_ec_get_host_event(struct cros_ec_device *ec_dev);
>
> +/**
> + * 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.
> + *
> + * This function is probably implemented using ktime_get_boot_ns(), but it's
> + * exposed here to make sure all cros_ec drivers use the same code path to get
> + * the time.
> + */
> +s64 cros_ec_get_time_ns(void);
> +
> #endif /* __LINUX_CROS_EC_PROTO_H */