Messages in this thread | | | Subject | Re: [PATCH] pps-gpio: use IRQ edge config when not capturing both edges | From | Rodolfo Giometti <> | Date | Tue, 12 Sep 2017 18:22:11 +0200 |
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On 12/09/2017 17:54, Tim Harvey wrote: > On Sun, Sep 10, 2017 at 3:43 AM, Rodolfo Giometti <giometti@enneenne.com> wrote: >> On 08/09/2017 21:53, Tim Harvey wrote: >>> >>> PPS signals with very short pulse-widths can be missed if their state >>> changes by the time the interrupt handler reads the GPIO pin state. >>> >>> To avoid this in the case where we are only looking for one edge we can >>> use the edge configuration for the pin state but fall back to reading the >>> pin if both edges are being watched. >> >> >> I disagree. The "rising_edge" status should be get from the hardware and not >> derived by an empirical computation. Or, at least, it should be specifically >> activated by setting something like this: >> >> pps { >> pinctrl-names = "default"; >> pinctrl-0 = <&pinctrl_pps>; >> >> gpios = <&gpio1 26 GPIO_ACTIVE_HIGH>; >> Yes-I-want-get-signal-status-in-an-epirical-way; >> >> compatible = "pps-gpio"; >> status = "okay"; >> }; >> >> This setting should also print a warning in order to be clear for the user >> that he/she should know what he/she is doing. >> >> Then the code should check also the compatibility with property >> "assert-falling-edge"... >> > > Hi Rodolfo, > > Do you agree with using the irq edge in general if/when it is > available to resolve the case where small pulse-widths can be caught? > > I assumed because pps-gpio is the one configuring the irq based on > info->capture_clear and info->assert_falling_edge that that it made > sense to use that logic again when handling the interrupt but there is > likely a call I can make to determine the irq (edge) type based on the > irq.
If you get the information from the hardware it's OK for me, otherwise you should enable this behavior by using proper DT property.
Ciao,
Rodolfo
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