On 13/04/2020 15:39, Drew Fustini wrote:
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"?
For this platforms the dynamic GPIO muxing/configuration is not supported, and GPIO block by itself
does not provide such functions as pullup/pulldown.
Before use the pin has to be configured like;
&am33xx_pinmux {
user_leds_s0: user_leds_s0 {
pinctrl-single,pins = <
AM33XX_PADCONF(AM335X_PIN_GPMC_A5, PIN_OUTPUT_PULLDOWN, MUX_MODE7) /* gpmc_a5.gpio1_21 */
AM33XX_PADCONF(AM335X_PIN_GPMC_A6, PIN_OUTPUT_PULLUP, MUX_MODE7) /* gpmc_a6.gpio1_22 */
AM33XX_PADCONF(AM335X_PIN_GPMC_A7, PIN_OUTPUT_PULLDOWN, MUX_MODE7) /* gpmc_a7.gpio1_23 */
AM33XX_PADCONF(AM335X_PIN_GPMC_A8, PIN_OUTPUT_PULLUP, MUX_MODE7) /* gpmc_a8.gpio1_24 */
>;
};
mmc1_pins: pinmux_mmc1_pins {
pinctrl-single,pins = <
AM33XX_PADCONF(AM335X_PIN_SPI0_CS1, PIN_INPUT, MUX_MODE7) /* spio0_cs1.gpio0_6 */
--
Best regards,
grygorii
