Messages in this thread |  | | From | Linus Walleij <> | Date | Mon, 22 Jan 2018 09:37:38 +0100 | Subject | Re: [PATCH] pinctrl: at91-pio4: add support for drive-strength property |
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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.
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.
> @@ -814,6 +834,19 @@ static void atmel_conf_pin_config_dbg_show(struct pinctrl_dev *pctldev, > seq_printf(s, "%s ", "open-drain"); > if (conf & ATMEL_PIO_SCHMITT_MASK) > seq_printf(s, "%s ", "schmitt"); > + if (conf & ATMEL_PIO_DRVSTR_MASK) { > + switch ((conf & ATMEL_PIO_DRVSTR_MASK) >> ATMEL_PIO_DRVSTR_OFFSET) { > + case ATMEL_PIO_DRVSTR_LO: > + seq_printf(s, "%s ", "low-drive"); > + break; > + case ATMEL_PIO_DRVSTR_ME: > + seq_printf(s, "%s ", "medium-drive"); > + break; > + case ATMEL_PIO_DRVSTR_HI: > + seq_printf(s, "%s ", "high-drive"); > + break;
But here you know what VDDIOP is, right?
So in debugfs you could actually print the real drive strength in mA, or both "medium-drive, %u mA"?
Yours, Linus Walleij
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