Messages in this thread | | | Date | Sun, 09 Dec 2018 14:07:59 +1100 | From | tom burkart <> | Subject | Re: [PATCH v9 3/4] dt-bindings: pps: pps-gpio PPS ECHO implementation |
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Quoting Rob Herring <robh@kernel.org>:
> On Mon, Nov 26, 2018 at 10:06 PM tom burkart <tom@aussec.com> wrote: >> >> Hi Rob, >> >> Quoting Rob Herring <robh@kernel.org>: >> >> > On Thu, Nov 22, 2018 at 3:49 AM Tom Burkart <tom@aussec.com> wrote: >> >> >> >> This patch implements the device tree changes required for the pps >> >> echo functionality for pps-gpio, that sysfs claims is available >> >> already. >> >> >> >> This patch was originally written by Lukas Senger as part of a masters >> >> thesis project and modified for inclusion into the linux kernel by Tom >> >> Burkart. >> >> >> >> Signed-off-by: Lukas Senger <lukas@fridolin.com> >> >> Signed-off-by: Tom Burkart <tom@aussec.com> >> >> --- >> >> Documentation/devicetree/bindings/pps/pps-gpio.txt | 9 +++++++++ >> >> 1 file changed, 9 insertions(+) >> >> >> >> diff --git a/Documentation/devicetree/bindings/pps/pps-gpio.txt >> >> b/Documentation/devicetree/bindings/pps/pps-gpio.txt >> >> index 1155d49c2699..e09f6f2405c5 100644 >> >> --- a/Documentation/devicetree/bindings/pps/pps-gpio.txt >> >> +++ b/Documentation/devicetree/bindings/pps/pps-gpio.txt >> >> @@ -7,10 +7,15 @@ Required properties: >> >> - compatible: should be "pps-gpio" >> >> - gpios: one PPS GPIO in the format described by ../gpio/gpio.txt >> >> >> >> +Additional required properties for the PPS ECHO functionality: >> >> +- echo-gpios: one PPS ECHO GPIO in the format described by >> ../gpio/gpio.txt >> >> +- echo-active-ms: duration in ms of the active portion of the echo pulse >> >> + >> >> Optional properties: >> >> - assert-falling-edge: when present, assert is indicated by a >> falling edge >> >> (instead of by a rising edge) >> >> - capture-clear: when present, also capture the PPS clear event >> >> +- invert-pps-echo: when present, invert the PPS ECHO pulse >> > >> > Why do you need this? Can't you just make the echo gpio GPIO_ACTIVE_LOW? >> > >> > BTW, using the flag probably should have been done for >> > 'assert-falling-edge' as well. >> >> The hardware I use expects a positive-going echo pulse, however, it >> was really easy to give users the option to have it inverted in case >> they use different hardware that expects a negative-going edge. > > It will be even easier to implement if you use GPIO_ACTIVE_LOW or > GPIO_ACTIVE_HIGH as appropriate. If the flag is set appropriately, > then gpiod_set_value(gpio, 1) asserts the pulse and > gpiod_set_value(gpio, 0) deasserts it no matter which way the h/w is > wired. You can then get rid of invert_pps_echo in the driver.
Hi Rob, sure we can do that, however, a hardware change will need a recompile of the kernel, rather than setting a flag. You still need something to help decide whether to use GPIO_ACTIVE_LOW or GPIO_ACTIVE_HIGH depending on what hardware is currently connected to the system.
I am happy to delete that code as well, if it makes you happy.
Tom
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