Messages in this thread | | | Date | Mon, 29 Jan 2018 13:01:30 -0600 | From | Rob Herring <> | Subject | Re: [PATCH] pinctrl: at91-pio4: add support for drive-strength property |
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On Mon, Jan 22, 2018 at 09:37:38AM +0100, Linus Walleij wrote: > On Thu, Jan 18, 2018 at 5:02 PM, Ludovic Desroches > <ludovic.desroches@microchip.com> wrote: > > > Add support for the drive-strength property. Usually its value is > > expressed in mA. Since the numeric value depends on VDDIOP voltage, > > the controller uses low, medium and high to define the drive-strengh. > > Aha I see. That's complex. It certainly results in a certain mA drive > strength in the end, but what you're saying is that this is not usually > what we configure. > > > The PIO controller accepts two values for the low drive: 0 or 1. Most > > of the time, we don't care about the drive strength, there is no need > > to change it, so 0 is considered as the default value. > > Do you mean default value as in "whatever the hardware was set > up as at boot time"? > > > The low-drive > > value won't be advertised through pinconf-pins file excepted if it > > except? > > > has been set explicitly in the device tree ie if its value is > > different from 0. > > > > Signed-off-by: Ludovic Desroches <ludovic.desroches@microchip.com> > > OK I think I get it. > > > Optional properties: > > - GENERIC_PINCONFIG: generic pinconfig options to use, bias-disable, > > -bias-pull-down, bias-pull-up, drive-open-drain, input-schmitt-enable, > > -input-debounce, output-low, output-high. > > +bias-pull-down, bias-pull-up, drive-open-drain, drive-strength, > > +input-schmitt-enable, input-debounce, output-low, output-high. > (...) > > + drive-strength = <ATMEL_PIO_DRVSTR_LO>; > > So you say you support this argument and it will be something like > > include/dt-bindings/pinctrl/at91.h:#define ATMEL_PIO_DRVSTR_LO 1 > include/dt-bindings/pinctrl/at91.h:#define ATMEL_PIO_DRVSTR_ME 2 > include/dt-bindings/pinctrl/at91.h:#define ATMEL_PIO_DRVSTR_HI 3 > > But the definition if generic drive strength is actually in mA.
Yes, and the reason we put unit suffixes on properties is to avoid differing units. > I think it is OK to deviate from stating it in mA, but you should > write this in the DT bindings so people do not get confused.
I don't think it is okay. If "drive-strength" doesn't work, then use a vendor specific property ("atmel,drive-strength"). Of course, I might forget this in the next version and tell you to use a standard property in mA.
Rob
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