On Fri, Mar 13, 2020 at 01:23:15PM +0800, Haojian Zhuang wrote:
> On Fri, 13 Mar 2020 at 08:38, Drew Fustini <pdp7pdp7@xxxxxxxxx> wrote:
> >
> > On Thu, Mar 12, 2020 at 1:43 PM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> > > Do we have a datasheet for this GPIO block somewhere? Should
> > > be the datasheet for the ASIC.
> >
> > I am looking at the AM335x reference manual [0] but I can not actually
> > find any references to pull-up/down or bias for GPIO pins. I guess I
> > was making of the mistake of assuming this would be something the gpio
> > pins support.
> >
> > > We already have the required .set_config() callback on the OMAP
> > > driver, it's just that it only uses it for debounce.
> > >
> > > The driver is a bit convoluted with register offsets in a struct
> > > omap_gpio_reg_offs depending on variant, but if they have
> > > a register for this I'd say just get hacking.
> > >
> > > If the GPIO driver is using pin control as back-end you are
> > > looking at something more complex similar to what Intel is
> > > doing inside drivers/pinctrl/intel/pinctrl-intel.c: this driver
> > > is just calling up to gpiochip_generic_config() which will
> > > try to configure the lines behind the GPIO using pin config,
> > > which works if the proper ranges are defined so the
> > > framework can map a GPIO line to a pin control pin.
> >
> > Thank you for the feedback, Linus.
> >
> > Upon further review of drivers/pinctrl/pinctrl-single.c, I am not
> > certain it actually supports pull-up/down.
> >
> > I see there is pcs_pinconf_clear_bias() and pcs_pinconf_bias_disable()
> > but I don't see a place where the PIN_CONFIG_BIAS_PULL_DOWN or
> > PIN_CONFIG_BIAS_PULL_UP get set.
> >
>
> /* 4 parameters */
> case PIN_CONFIG_BIAS_DISABLE:
> pcs_pinconf_clear_bias(pctldev, pin);
> break;
> case PIN_CONFIG_BIAS_PULL_DOWN:
> case PIN_CONFIG_BIAS_PULL_UP:
> if (arg)
> pcs_pinconf_clear_bias(pctldev, pin);
> /* fall through */
> case PIN_CONFIG_INPUT_SCHMITT_ENABLE:
> data &= ~func->conf[i].mask;
> if (arg)
> data |= func->conf[i].enable;
> else
> data |= func->conf[i].disable;
> break;
>
> Because it does fall through, pullup/pulldown is set in the snippet of
> "PIN_CONFIG_INPUT_SCHMITT_ENABLE".
>
> Best Regards
> Haojian
Thank you for the insights, Haojian and Linus.
I've added debug print statements and it seems that pcs_pinconf_set()
is never called on the BeagleBone (TI AM3358) either during boot or
when gpiomon runs with bias switch that invokes GPIO_GET_LINEEVENT_IOCTL
with GPIOHANDLE_REQUEST_BIAS_PULL_UP flag.
The pinctrl-single driver and gpio-omap driver bind as a result of these
device tree nodes in arch/arm/boot/dts/am33xx-l4.dtsi:
am33xx_pinmux: pinmux@800 {
compatible = "pinctrl-single";
reg = <0x800 0x238>;
#pinctrl-cells = <1>;
pinctrl-single,register-width = <32>;
pinctrl-single,function-mask = <0x7f>;
};
gpio0: gpio@0 {
compatible = "ti,omap4-gpio";
gpio-controller;
#gpio-cells = <2>;
interrupt-controller;
#interrupt-cells = <2>;
reg = <0x0 0x1000>;
interrupts = <96>;
gpio-line-names =
"MDIO_DATA", // 0
<snip>
I see in Documentation/devicetree/bindings/pinctrl/pinctrl-single.txt
"pinctrl-single" means that pinconf isn't supported.
I believe this is why pcs_pinconf_set() never gets called.
Any suggestions as to how I could proceed?
Is it reasonable to change the compatible to "pinconf-single"?
Thank You,
Drew
