On Mon, Nov 26, 2018 at 9:57 PM tom burkart <tom@xxxxxxxxxx> wrote: > > Hi Rob, > > Quoting Rob Herring <robh@xxxxxxxxxx>: > > > On Sat, Nov 17, 2018 at 6:35 PM tom burkart <tom@xxxxxxxxxx> wrote: > >> > >> Quoting Rob Herring <robh@xxxxxxxxxx>: > >> > >> > On Sat, Nov 17, 2018 at 4:35 AM tom burkart <tom@xxxxxxxxxx> wrote: > >> >> > >> >> Quoting Rob Herring <robh@xxxxxxxxxx>: > >> >> > >> >> > On Wed, Nov 14, 2018 at 11:54:29PM +1100, Tom Burkart wrote: > >> >> >> This patch changes the devicetree bindings for the pps-gpio driver > >> >> >> from the integer based ABI to the descriptor based ABI. > >> >> > ? That has nothing to do with DT. > >> >> > >> >> I believe it does, as the change in ABI forces a rename in the DT > >> >> naming convention. > >> >> This is due to the descriptor based ABI appending "-gpio" or > >> "-gpios" (see > >> >> Documentation/gpio/base.txt.) > >> >> Admittedly, I may have called it by the wrong name due to ignorance, > >> >> my apologies. > >> > > >> > If what you say is correct, then you can't change this driver. You'll > >> > break compatibility with any existing DT. > >> > > >> > Changing the binding reasoning should purely be that this is the > >> > preferred form. Bindings must be independent from changing kernel > >> > APIs. > >> > >> See comments from Philip Zabel. I misread the documentation and this > >> has now been corrected in v8 of the patch. I hope that eliminates all > >> comments made above. > >> > >> >> >> It also adds > >> >> >> documentation for the device tree capture-clear option. The legacy > >> >> >> device tree entry for the GPIO pin is supported. > >> >> >> > >> >> >> Signed-off-by: Tom Burkart <tom@xxxxxxxxxx> > >> >> >> --- > >> >> >> Documentation/devicetree/bindings/pps/pps-gpio.txt | 8 ++++++-- > >> >> >> 1 file changed, 6 insertions(+), 2 deletions(-) > >> >> >> > >> >> >> diff --git a/Documentation/devicetree/bindings/pps/pps-gpio.txt > >> >> >> b/Documentation/devicetree/bindings/pps/pps-gpio.txt > >> >> >> index 3683874832ae..6c9fc0998d94 100644 > >> >> >> --- a/Documentation/devicetree/bindings/pps/pps-gpio.txt > >> >> >> +++ b/Documentation/devicetree/bindings/pps/pps-gpio.txt > >> >> >> @@ -5,19 +5,23 @@ a GPIO pin. > >> >> >> > >> >> >> Required properties: > >> >> >> - compatible: should be "pps-gpio" > >> >> >> -- gpios: one PPS GPIO in the format described by ../gpio/gpio.txt > >> >> >> +- pps-gpios: one PPS GPIO in the format described by ../gpio/gpio.txt > >> >> >> +Alternatively (DEPRECATED), instead of pps-gpios above, it may have: > >> >> >> +- gpios: one PPS GPIO as above > >> >> >> > >> >> >> 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 > >> >> > > >> >> > Is this a h/w thing? or driver configuration? > >> >> > >> >> Driver configuration. Most of the code was present in the driver, yet > >> >> it was not documented, or usable due to a two line (code) omission > >> >> (the value was not being fetched from DT). > >> > > >> > So what determines how you want to configure this? If the user will > >> > want to change it, then it should be a sysfs attr and exposed to > >> > userspace. If it depends on h/w config for a board then it can be in > >> > DT. > >> > >> Sorry, I misled you somewhat. If the PPS pulse active transition from > >> the hardware is on the falling edge, this flag is required to get the > >> OS to use that as the active transition. This would not change at the > >> user's whim but rather it is dependent on connected hardware. > > > > This description sounds more like 'assert-falling-edge' than 'capture-clear'. > > > > I'm still not clear on what 'capture-clear' is. > > Ignoring my patch for a minute, the pps_gpio_irq_handler will only > report a pps PPS_CAPTURECLEAR event if 'capture-clear' is set. As the > current pps-gpio driver is not able to set this flag, it cannot ever > report a PPS_CAPTURECLEAR event. > > My patch adds the ability to set this flag and adds the documentation > to go with it. > Admittedly, I do not require this functionality for what I want, but > working with the code, I noticed the omission and decided to add it > for someone else to use it, if they need it. > > I am happy to remove this out of my patch, if you feel this to be the > best way forward. I found this prior discussion on adding this[1]. Seems to me this should be userspace configurable if the GPIO line can interrupt on both edges. We shouldn't need a DT property to determine that. Rob [1] https://lore.kernel.org/patchwork/patch/557781/
