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    SubjectRe: [RFC 08/11] gpiolib: cdev: Add hardware timestamp clock type
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    On 30/07/2021 03:33, Dipen Patel wrote:
    >
    > On 7/9/21 1:30 AM, Jon Hunter wrote:
    >> On 26/06/2021 00:55, 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);
    >>> + }
    >>> +
    >>> return ktime_get_ns();
    >>> }
    >>
    >> Looking at line_event_timestamp() and the callers of this function, it
    >> appears that this should always return nanoseconds. Does
    >> gpiod_get_hw_timestamp() return nanoseconds?
    > Yes, it returns in ns to align with line_event_timestamp.


    It might be worth updating the function name to
    gpiod_get_hw_timestamp_ns() so that this is clear.

    Jon

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    nvpublic

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