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Commit e397824b authored by Jan Kundrát's avatar Jan Kundrát Committed by Greg Kroah-Hartman
Browse files

gpio: serial: max310x: Support open-drain configuration for GPIOs 

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: default avatarJan Kundrát <jan.kundrat@cesnet.cz>
Reviewed-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 7d09995d

drivers/tty/serial/max310x.c

+22 −0
Original line number Original line Diff line number Diff line
@@ -1159,6 +1159,27 @@ static int max310x_gpio_direction_output(struct gpio_chip *chip, 




	return 0;

	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

#endif





static int max310x_probe(struct device *dev, struct max310x_devtype *devtype,

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.get		= max310x_gpio_get;

	s->gpio.direction_output= max310x_gpio_direction_output;

	s->gpio.direction_output= max310x_gpio_direction_output;

	s->gpio.set		= max310x_gpio_set;

	s->gpio.set		= max310x_gpio_set;

	s->gpio.set_config	= max310x_gpio_set_config;

	s->gpio.base		= -1;

	s->gpio.base		= -1;

	s->gpio.ngpio		= devtype->nr * 4;

	s->gpio.ngpio		= devtype->nr * 4;

	s->gpio.can_sleep	= 1;

	s->gpio.can_sleep	= 1;