Linux/AM3352: Change gpio logic level at kernel boot

Hi Ankur,

I was using logic analyzer to see the logic level on the pin. When kernel starts booting the gpio2_28 pin goes low and after few millisecond it goes to high

Can you share your dts file? Perhaps you haven't pinmuxed the gpio correctly.

Also you can have a look at drivers/leds/leds-gpio.c and hardcode the gpio level to active high in gpio_led_set(), which means setting level to 1.

Best Regards,
Yordan

Hi Yordan,

I am using device tree derived from AM33xx.dtsi. Any change in the leds-gpio.c is not required because I am able to set the led value from the device tree. I suspect that code in gpio driver (code in file gpio-omap.c) is setting gpio2_28 low.

Thanks & Regards,
Ankur

Ankur Pawar said:

When kernel starts booting the gpio2_28 pin goes low and after few millisecond it goes to high.

1. Have you tried halting at a u-boot prompt and checking the state of the pin?  Are you positive the pin is in the desired state while u-boot is executing?  Perhaps you should be focused on u-boot instead of the kernel.  This would be a quick test to confirm either way.
2. How are you configuring the gpio2_28 pinmuxing in your dts?
3. Have you done anything else in the dts to attempt to configure the state of this pin?  Please share snippets (or the whole thing).

1. U-boot
making GPIO2_28 high to low then high in u-boot function board_late_init()

if (!gpio_request(GPIO_UART5_CTS, "")) {
ret = gpio_direction_output(GPIO_UART5_CTS, 0);
if (ret < 0)
puts("gpio drirection failed\n");
ret = gpio_set_value(GPIO_UART5_CTS, 0);
if (ret < 0)
puts("gpio set value failed\n");

puts("start delay\n");
udelay(90000);
puts("delay over\n");
gpio_set_value(GPIO_UART5_CTS, 1);
if (ret < 0)
puts("gpio set value failed\n");
else
puts("GPIO_UART5_CTS gpio set to 1\n");
}
else
{
puts("GPIO_UART5_CTS request failed!\n");
}

2. In device tree
gpio_enable_pins: pinmux_gpio_enable_pins {
pinctrl-single,pins = <
0xF8 (PIN_INPUT_PULLUP | MUX_MODE7) /* mmc0_dat1.gpio2_28.uart5_cts */
>;
};
gpio2: gpio@481ac000 {
compatible = "ti,omap4-gpio";
ti,hwmods = "gpio3";
clocks = <&l4ls_gclk>, <&gpio2_dbclk>;
clock-names = "fck", "dbclk";
gpio-controller;
#gpio-cells = <2>;
interrupt-controller;
#interrupt-cells = <1>;
reg = <0x481ac000 0x1000>;
interrupts = <32>;
};

gpio2_28enable {
compatible = "gpio-leds";
pinctrl-names = "default";
pinctrl-0 = <&gpio_enable_pins>;

p28@0 {
label = "gpio2_28";
gpios = <&gpio2 28 GPIO_ACTIVE_HIGH>
default-state = "on";
};
};