From: Kent Gibson <warthog618@gmail.com>
To: Dipen Patel <dipenp@nvidia.com>
Cc: thierry.reding@gmail.com, jonathanh@nvidia.com,
linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org,
linux-gpio@vger.kernel.org, linus.walleij@linaro.org,
bgolaszewski@baylibre.com, devicetree@vger.kernel.org,
linux-doc@vger.kernel.org, robh+dt@kernel.org
Subject: Re: [RFC 08/11] gpiolib: cdev: Add hardware timestamp clock type
Date: Thu, 1 Jul 2021 22:24:33 +0800 [thread overview]
Message-ID: <20210701142433.GC34285@sol> (raw)
In-Reply-To: <20210625235532.19575-9-dipenp@nvidia.com>
On Fri, Jun 25, 2021 at 04:55:29PM -0700, Dipen Patel wrote:
> This patch adds new clock type for the GPIO controller which can
> timestamp gpio lines using hardware means. To expose such
> functionalities to the userspace, code has been added in this patch
> where during line create call, it checks for new clock type and if
> requested, calls hardware timestamp related API from gpiolib.c.
> During line change event, it retrieves timestamp in nano seconds by
> calling gpiod_get_hw_timestamp API from gpiolib.c. At the line release,
> it disables this functionality by calling gpiod_hw_timestamp_control.
>
> Signed-off-by: Dipen Patel <dipenp@nvidia.com>
> ---
> drivers/gpio/gpiolib-cdev.c | 65 +++++++++++++++++++++++++++++++++++--
> include/uapi/linux/gpio.h | 1 +
> 2 files changed, 64 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
> index 1631727bf0da..9f98c727e937 100644
> --- a/drivers/gpio/gpiolib-cdev.c
> +++ b/drivers/gpio/gpiolib-cdev.c
> @@ -518,6 +518,7 @@ struct linereq {
> GPIO_V2_LINE_DRIVE_FLAGS | \
> GPIO_V2_LINE_EDGE_FLAGS | \
> GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME | \
> + GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE | \
> GPIO_V2_LINE_BIAS_FLAGS)
>
> static void linereq_put_event(struct linereq *lr,
> @@ -540,9 +541,20 @@ static void linereq_put_event(struct linereq *lr,
>
> static u64 line_event_timestamp(struct line *line)
> {
> + bool block;
> +
> if (test_bit(FLAG_EVENT_CLOCK_REALTIME, &line->desc->flags))
> return ktime_get_real_ns();
>
> + if (test_bit(FLAG_EVENT_CLOCK_HARDWARE, &line->desc->flags)) {
> + if (irq_count())
> + block = false;
> + else
> + block = true;
> +
> + return gpiod_get_hw_timestamp(line->desc, block);
> + }
> +
Use in_task() instead of block?
> return ktime_get_ns();
> }
>
> @@ -828,6 +840,7 @@ static int edge_detector_setup(struct line *line,
> return ret;
>
> line->irq = irq;
> +
> return 0;
> }
>
Remove gratuitous whitespace changes.
If you dislike the formatting then suggest it in a separate patch.
> @@ -891,7 +904,6 @@ static int gpio_v2_line_flags_validate(u64 flags)
> /* Return an error if an unknown flag is set */
> if (flags & ~GPIO_V2_LINE_VALID_FLAGS)
> return -EINVAL;
> -
> /*
> * Do not allow both INPUT and OUTPUT flags to be set as they are
> * contradictory.
> @@ -900,6 +912,14 @@ static int gpio_v2_line_flags_validate(u64 flags)
> (flags & GPIO_V2_LINE_FLAG_OUTPUT))
> return -EINVAL;
>
Same here.
> + /*
> + * Do not mix with any other clocks if hardware assisted timestamp is
> + * asked.
> + */
> + if ((flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME) &&
> + (flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE))
> + return -EINVAL;
> +
The comment is very hw timestamp centric. It should just be something
along the lines of "only allow one event clock source".
> /* Edge detection requires explicit input. */
> if ((flags & GPIO_V2_LINE_EDGE_FLAGS) &&
> !(flags & GPIO_V2_LINE_FLAG_INPUT))
> @@ -992,6 +1012,8 @@ static void gpio_v2_line_config_flags_to_desc_flags(u64 flags,
>
> assign_bit(FLAG_EVENT_CLOCK_REALTIME, flagsp,
> flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME);
> + assign_bit(FLAG_EVENT_CLOCK_HARDWARE, flagsp,
> + flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE);
> }
>
> static long linereq_get_values(struct linereq *lr, void __user *ip)
> @@ -1139,6 +1161,18 @@ static long linereq_set_config_unlocked(struct linereq *lr,
> int val = gpio_v2_line_config_output_value(lc, i);
>
> edge_detector_stop(&lr->lines[i]);
> +
> + /*
> + * Assuming line was input before and hardware
> + * assisted timestamp only timestamps the input
> + * lines.
> + */
> + if (gpiod_is_hw_timestamp_enabled(desc)) {
> + ret = gpiod_hw_timestamp_control(desc, false);
> + if (ret)
> + return ret;
> + }
> +
So if you fail to disable the hw timestamp then you fail the set_config?
Does that make sense?
It should be impossible to fail, as per the preceding edge_detector_stop(),
or any failure in this context is irrelevant and so can be ignored.
> ret = gpiod_direction_output(desc, val);
> if (ret)
> return ret;
> @@ -1152,6 +1186,13 @@ static long linereq_set_config_unlocked(struct linereq *lr,
> polarity_change);
> if (ret)
> return ret;
> +
> + /* Check if new config sets hardware assisted clock */
> + if (flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE) {
> + ret = gpiod_hw_timestamp_control(desc, true);
> + if (ret)
> + return ret;
> + }
> }
>
The error code here can come from the pinctrl timestamp_control(), so it
should be sanitised before being returned to userspace.
> blocking_notifier_call_chain(&desc->gdev->notifier,
> @@ -1281,8 +1322,12 @@ static void linereq_free(struct linereq *lr)
>
> for (i = 0; i < lr->num_lines; i++) {
> edge_detector_stop(&lr->lines[i]);
> - if (lr->lines[i].desc)
> + if (lr->lines[i].desc) {
> + if (gpiod_is_hw_timestamp_enabled(lr->lines[i].desc))
> + gpiod_hw_timestamp_control(lr->lines[i].desc,
> + false);
> gpiod_free(lr->lines[i].desc);
> + }
Potential race on gpiod_is_hw_timestamp_enabled() and the call to
gpiod_hw_timestamp_control()?
Why not put the gpiod_is_hw_timestamp_enabled() check inside
gpiod_hw_timestamp_control()?
And the gpiod_hw_timestamp_control() call should be moved inside
gpiod_free(), or more correctly gpiod_free_commit().
i.e. whenever you free the gpio you release any associated hw timestamp.
> }
> kfifo_free(&lr->events);
> kfree(lr->label);
> @@ -1409,6 +1454,15 @@ static int linereq_create(struct gpio_device *gdev, void __user *ip)
> flags & GPIO_V2_LINE_EDGE_FLAGS);
> if (ret)
> goto out_free_linereq;
> +
> + /*
> + * Check if hardware assisted timestamp is requested
> + */
> + if (flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE) {
> + ret = gpiod_hw_timestamp_control(desc, true);
> + if (ret)
> + goto out_free_linereq;
> + }
> }
>
Comment can fit on one line, and probably isn't even necessary - the
code is clear enough.
> blocking_notifier_call_chain(&desc->gdev->notifier,
> @@ -1956,8 +2010,15 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
> if (test_bit(FLAG_EDGE_FALLING, &desc->flags))
> info->flags |= GPIO_V2_LINE_FLAG_EDGE_FALLING;
>
> + /*
> + * Practically it is possible that user will want both the real time
> + * and hardware timestamps on GPIO events, for now however lets just
> + * work with either clocks
> + */
> if (test_bit(FLAG_EVENT_CLOCK_REALTIME, &desc->flags))
> info->flags |= GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME;
> + else if (test_bit(FLAG_EVENT_CLOCK_HARDWARE, &desc->flags))
> + info->flags |= GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE;
>
If there is any need or intent to support multiple clock sources then
avoid creeping API changes and add it now.
Either way, drop the comment.
> debounce_period_us = READ_ONCE(desc->debounce_period_us);
> if (debounce_period_us) {
> diff --git a/include/uapi/linux/gpio.h b/include/uapi/linux/gpio.h
> index eaaea3d8e6b4..d360545b4c21 100644
> --- a/include/uapi/linux/gpio.h
> +++ b/include/uapi/linux/gpio.h
> @@ -80,6 +80,7 @@ enum gpio_v2_line_flag {
> GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN = _BITULL(9),
> GPIO_V2_LINE_FLAG_BIAS_DISABLED = _BITULL(10),
> GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME = _BITULL(11),
> + GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE = _BITULL(12),
> };
>
> /**
> --
> 2.17.1
>
Cheers,
Kent.
next prev parent reply other threads:[~2021-07-01 14:24 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-25 23:55 [RFC 00/11] Intro to Hardware timestamping engine Dipen Patel
2021-06-25 23:55 ` [RFC 01/11] Documentation: Add HTE subsystem guide Dipen Patel
2021-07-04 18:55 ` Jonathan Cameron
2021-07-27 23:44 ` Dipen Patel
2021-08-01 15:24 ` Jonathan Cameron
2021-06-25 23:55 ` [RFC 02/11] drivers: Add HTE subsystem Dipen Patel
2021-06-27 17:40 ` Randy Dunlap
2021-07-04 20:15 ` Jonathan Cameron
2021-07-04 20:45 ` Jonathan Cameron
2021-07-28 5:12 ` Dipen Patel
2021-08-01 16:48 ` Jonathan Cameron
2021-07-28 4:38 ` Dipen Patel
2021-08-01 16:13 ` Jonathan Cameron
2021-09-14 5:43 ` Dipen Patel
2021-09-26 15:42 ` Jonathan Cameron
2021-07-05 7:30 ` Greg KH
2021-07-28 0:34 ` Dipen Patel
2021-06-25 23:55 ` [RFC 03/11] hte: Add tegra194 HTE kernel provider Dipen Patel
2021-07-01 14:21 ` Kent Gibson
2021-07-28 23:59 ` Dipen Patel
2021-07-30 7:01 ` Dipen Patel
2021-07-31 15:43 ` Kent Gibson
2021-08-03 22:40 ` Dipen Patel
2021-08-03 23:02 ` Kent Gibson
2021-08-07 2:41 ` Dipen Patel
2021-08-07 3:07 ` Kent Gibson
2021-08-07 4:52 ` Dipen Patel
2021-08-07 4:51 ` Kent Gibson
2021-08-07 5:35 ` Dipen Patel
2021-08-07 5:42 ` Kent Gibson
2021-08-07 5:47 ` Dipen Patel
2021-07-04 20:27 ` Jonathan Cameron
2021-07-29 2:42 ` Dipen Patel
2021-07-08 23:33 ` Michał Mirosław
2021-07-29 2:43 ` Dipen Patel
2021-06-25 23:55 ` [RFC 04/11] dt-bindings: Add HTE bindings Dipen Patel
2021-06-27 10:56 ` Linus Walleij
2021-07-30 1:32 ` Dipen Patel
2021-07-01 14:02 ` Rob Herring
2021-07-30 1:56 ` Dipen Patel
2021-07-01 15:54 ` Rob Herring
2021-07-30 1:58 ` Dipen Patel
2021-06-25 23:55 ` [RFC 05/11] hte: Add Tegra194 IRQ HTE test driver Dipen Patel
2021-06-27 17:42 ` Randy Dunlap
2021-06-25 23:55 ` [RFC 06/11] gpiolib: Add HTE support Dipen Patel
2021-06-27 11:41 ` Linus Walleij
2021-07-01 14:24 ` Kent Gibson
2021-07-30 2:25 ` Dipen Patel
2021-07-31 5:13 ` Kent Gibson
2021-06-25 23:55 ` [RFC 07/11] gpio: tegra186: Add HTE in gpio-tegra186 driver Dipen Patel
2021-06-25 23:55 ` [RFC 08/11] gpiolib: cdev: Add hardware timestamp clock type Dipen Patel
2021-06-27 11:38 ` Linus Walleij
2021-06-27 11:49 ` Linus Walleij
2021-07-30 3:16 ` Dipen Patel
2021-07-01 14:24 ` Kent Gibson [this message]
2021-07-30 3:07 ` Dipen Patel
2021-07-31 6:05 ` Kent Gibson
2021-08-03 22:41 ` Dipen Patel
2021-08-03 22:38 ` Kent Gibson
2021-07-09 8:30 ` Jon Hunter
2021-07-30 2:33 ` Dipen Patel
2021-08-03 16:42 ` Jon Hunter
2021-08-03 22:51 ` Dipen Patel
2021-08-03 23:09 ` Kent Gibson
2021-06-25 23:55 ` [RFC 09/11] tools: gpio: Add new hardware " Dipen Patel
2021-06-27 11:36 ` Linus Walleij
2021-07-30 3:17 ` Dipen Patel
2021-07-31 6:16 ` Kent Gibson
2021-08-11 9:11 ` Linus Walleij
2021-06-25 23:55 ` [RFC 10/11] hte: Add tegra GPIO HTE test driver Dipen Patel
2021-06-27 17:43 ` Randy Dunlap
2021-06-25 23:55 ` [RFC 11/11] MAINTAINERS: Added HTE Subsystem Dipen Patel
2021-06-27 13:07 ` [RFC 00/11] Intro to Hardware timestamping engine Andy Shevchenko
2021-06-27 14:40 ` Linus Walleij
2021-06-28 12:02 ` Andy Shevchenko
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