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Subject: Re: [PATCH v2 05/18] platform: chrome: cros-ec: record event
 timestamp in the hard irq
To:     Gwendal Grignou <gwendal@chromium.org>, briannorris@chromium.org,
        jic23@kernel.org, knaack.h@gmx.de, lars@metafoo.de,
        pmeerw@pmeerw.net, lee.jones@linaro.org, bleung@chromium.org,
        dianders@chromium.org, groeck@chromium.org,
        fabien.lahoudere@collabora.com
Cc:     linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org,
        Rushikesh S Kadam <rushikesh.s.kadam@intel.com>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Jett Rink <jettrink@chromium.org>
References: <20191021055403.67849-1-gwendal@chromium.org>
 <20191021055403.67849-6-gwendal@chromium.org>
From:   Enric Balletbo i Serra <enric.balletbo@collabora.com>
Message-ID: <176f0ed8-5dd8-ca79-17c6-3b2e2f3a1aaa@collabora.com>
Date:   Tue, 22 Oct 2019 12:03:34 +0200
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Hi Gwendal,

Cc'ing some ISHTP people as I don't have the hardware. If possible, could any of
you give us your Tested-by tag?

On 21/10/19 7:53, Gwendal Grignou 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>

Gwendal, I am right saying that this patch can be applied independently of the
others and has no dependencies?

Thanks,
 Enric

> ---
> 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           | 12 +++++++++++-
>  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, 44 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/platform/chrome/cros_ec.c b/drivers/platform/chrome/cros_ec.c
> index 9b2d07422e175..739f3cffe26e3 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;
> @@ -141,7 +150,8 @@ 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_ishtp.c b/drivers/platform/chrome/cros_ec_ishtp.c
> index 25ca2c894b4de..5c848f22b44b4 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 7d10d909435ff..3c77496e164da 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 691f9e953a96a..b183024fef1f6 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

nit: s/e/E/

> + *     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.
> + *
> + * 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 */
>