gpio: serial: max310x: Support open-drain configuration for GPIOs (e397824b) · Commits · 戴 / test

The push-pull vs. open-drain are the only supported output modes. The inputs are always unconditionally equipped with weak pull-downs. That's the only mode, so there's probably no point in exporting that. I wonder if it's worthwhile to provide a custom dbg_show method to indicate the current status of the outputs, though. This patch and [1] for i2c-gpio together make it possible to bit-bang an I2C bus over GPIOs of an UART which is connected via SPI :). Yes, this is crazy, but it's fast enough (while on a 26Mhz SPI HW bus with a dual-core 1.6GHz CPU) to drive an I2C bus at 200kHz, according to my scope. [1] https://patchwork.ozlabs.org/patch/852591/ Signed-off-by:

Jan Kundrát <jan.kundrat@cesnet.cz> Reviewed-by:

Linus Walleij <linus.walleij@linaro.org> Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/max310x.c

+22 −0

Original line number	Diff line number	Diff line
		@@ -1159,6 +1159,27 @@ static int max310x_gpio_direction_output(struct gpio_chip *chip,

		return 0;
		}

		static int max310x_gpio_set_config(struct gpio_chip *chip, unsigned int offset,
		unsigned long config)
		{
		struct max310x_port *s = gpiochip_get_data(chip);
		struct uart_port *port = &s->p[offset / 4].port;

		switch (pinconf_to_config_param(config)) {
		case PIN_CONFIG_DRIVE_OPEN_DRAIN:
		max310x_port_update(port, MAX310X_GPIOCFG_REG,
		1 << ((offset % 4) + 4),
		1 << ((offset % 4) + 4));
		return 0;
		case PIN_CONFIG_DRIVE_PUSH_PULL:
		max310x_port_update(port, MAX310X_GPIOCFG_REG,
		1 << ((offset % 4) + 4), 0);
		return 0;
		default:
		return -ENOTSUPP;
		}
		}
		#endif

		static int max310x_probe(struct device dev, struct max310x_devtype devtype,
		@@ -1302,6 +1323,7 @@ static int max310x_probe(struct device dev, struct max310x_devtype devtype,
		s->gpio.get = max310x_gpio_get;
		s->gpio.direction_output= max310x_gpio_direction_output;
		s->gpio.set = max310x_gpio_set;
		s->gpio.set_config = max310x_gpio_set_config;
		s->gpio.base = -1;
		s->gpio.ngpio = devtype->nr * 4;
		s->gpio.can_sleep = 1;

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