Reading GPIOs with DM_GPIO before device tree is loaded

[Hugo Villeneuve]

Hi,
in board_early_init_f(), i call a custom function get_som_revision() to read some GPIOs that are used to determine the SOM revision. This function basically sets the iomux, and then uses gpio_request/gpio_direction_input/gpio_get_value functions to read the GPIOs. Then, this SOM revision information is used in  board_fit_config_name_match() to decide which device tree to load.

This works perfectly fine without CONFIG_DM_GPIO. However, if I enable CONFIG_DM_GPIO, it doesn't work anymore. There is an error when calling gpio_request().

What is the correct way to read GPIOs BEFORE any device tree is loaded?

My board uses an MX6Q SOM.

Here is part of the code I am using:

========================================
static iomux_v3_cfg_t const boardcfg_pads[] = {
	MX6_PAD_DISP0_DAT15__GPIO5_IO09	| MUX_PAD_CTRL(NO_PAD_CTRL),
	MX6_PAD_DISP0_DAT8__GPIO4_IO29	| MUX_PAD_CTRL(NO_PAD_CTRL),
	MX6_PAD_DISP0_DAT0__GPIO4_IO21	| MUX_PAD_CTRL(NO_PAD_CTRL),
	MX6_PAD_ENET_RXD0__GPIO1_IO27	| MUX_PAD_CTRL(NO_PAD_CTRL),
	MX6_PAD_ENET_RXD1__GPIO1_IO26	| MUX_PAD_CTRL(NO_PAD_CTRL),
};

static int som_revision = -1;

static const int boardcfg_gpio[] = {
	IMX_GPIO_NR(5, 9),
	IMX_GPIO_NR(4, 29),
	IMX_GPIO_NR(4, 21),
	IMX_GPIO_NR(1, 27),
	IMX_GPIO_NR(1, 26),
};

static void get_som_revision(void)
{
	int i;
	int rc;

	som_revision = 0;

	SETUP_IOMUX_PADS(boardcfg_pads);

	for (i = 0; i < ARRAY_SIZE(boardcfg_gpio); ++i) {
		int v;

		rc = gpio_request(boardcfg_gpio[i], "som-revision-gpio");
		if (rc) {
			printf("%s(): gpio request %d failed\n", __func__, i);
			som_revision = -1;
			return;
		}

		gpio_direction_input(boardcfg_gpio[i]);
		v = gpio_get_value(boardcfg_gpio[i]);

		if ((v == 0) || (v == 1))
			som_revision |= v << i;
		else {
			som_revision = -1;
			return;
		}
	}
}

int board_early_init_f(void)
{
	setup_iomux_uart();
	get_som_revision();

	return 0;
}

========================================



Thank you,
Hugo Villeneuve.