[PATCH v2] gpio: serial: max310x: Support open-drain configuration for GPIOs
From: Jan Kundrát <hidden>
Date: 2018-01-09 16:23:48
Also in:
linux-gpio
Subsystem:
the rest, tty layer and serial drivers · Maintainers:
Linus Torvalds, Greg Kroah-Hartman, Jiri Slaby
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 <redacted> Reviewed-by: Linus Walleij <redacted> --- drivers/tty/serial/max310x.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+)
diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c
index 97576ff791db..39f635812077 100644
--- a/drivers/tty/serial/max310x.c
+++ b/drivers/tty/serial/max310x.c@@ -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;
--
2.14.3