Re: [RFC 08/11] gpiolib: cdev: Add hardware timestamp clock type

[Jon Hunter]

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@xxxxxxxxxx>
> > > ---
> > >   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