On Mon, 3 Jun 2024 20:37:10 +0800
Hui Wang <hui.wang@xxxxxxxxxxxxx> wrote:
Hi Hui,
> Certain designs connect a gpio to the reset pin, and the reset pin
> needs to be setup correctly before accessing the chip.
>
> Here adding a function to handle the reset pin. This change has no
> impact if there is no reset_gpios defined in the device tree.
>
> Signed-off-by: Hui Wang <hui.wang@xxxxxxxxxxxxx>
> ---
> drivers/tty/serial/sc16is7xx.c | 22 ++++++++++++++++++++++
> drivers/tty/serial/sc16is7xx.h | 2 ++
> drivers/tty/serial/sc16is7xx_i2c.c | 2 ++
> drivers/tty/serial/sc16is7xx_spi.c | 2 ++
> 4 files changed, 28 insertions(+)
>
> diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
> index bf0065d1c8e9..53bfb603b03c 100644
> --- a/drivers/tty/serial/sc16is7xx.c
> +++ b/drivers/tty/serial/sc16is7xx.c
> @@ -19,6 +19,7 @@
> #include <linux/kthread.h>
> #include <linux/mod_devicetable.h>
> #include <linux/module.h>
> +#include <linux/of_gpio.h>
> #include <linux/property.h>
> #include <linux/regmap.h>
> #include <linux/sched.h>
> @@ -1467,6 +1468,27 @@ static const struct serial_rs485 sc16is7xx_rs485_supported = {
> .delay_rts_after_send = 1, /* Not supported but keep returning -EINVAL */
> };
>
> +void sc16is7xx_setup_reset_pin(struct device *dev)
Potentially rename to sc16is7xx_reset() based on my comments below
about software reset.
> +{
> + struct device_node *np = dev->of_node;
> + int reset_gpio, err;
> +
> + reset_gpio = of_get_named_gpio(np, "reset-gpios", 0);
Maybe use devm_gpiod_get_optional() to simplify and avoid OF-specific
code.
> + if (!gpio_is_valid(reset_gpio))
> + return;
> +
> + err = devm_gpio_request_one(dev, reset_gpio, GPIOF_OUT_INIT_LOW,
> + "sc16is7xx-reset");
> + if (err) {
> + dev_err(dev, "failed to request sc16is7xx-reset-gpios: %d\n", err);
> + return;
When this error happens, you return no error to the calling function,
why? If you specify a reset GPIO in your device tree, and you cannot use
it, seems like an error worth reporting.
> + }
> +
> + /* Deassert the reset pin */
Do you respect the manufacturer's minimum reset pulse width? The
datasheet states that its 3 us, so maybe add a delay before deassertion.
> + gpio_set_value_cansleep(reset_gpio, 1);
> +}
> +EXPORT_SYMBOL_GPL(sc16is7xx_setup_reset_pin);
> +
> int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
> struct regmap *regmaps[], int irq)
> {
> diff --git a/drivers/tty/serial/sc16is7xx.h b/drivers/tty/serial/sc16is7xx.h
> index afb784eaee45..f4ae114cc41a 100644
> --- a/drivers/tty/serial/sc16is7xx.h
> +++ b/drivers/tty/serial/sc16is7xx.h
> @@ -33,6 +33,8 @@ const char *sc16is7xx_regmap_name(u8 port_id);
>
> unsigned int sc16is7xx_regmap_port_mask(unsigned int port_id);
>
> +void sc16is7xx_setup_reset_pin(struct device *dev);
> +
> int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
> struct regmap *regmaps[], int irq);
>
> diff --git a/drivers/tty/serial/sc16is7xx_i2c.c b/drivers/tty/serial/sc16is7xx_i2c.c
> index 3ed47c306d85..9833c3b935c2 100644
> --- a/drivers/tty/serial/sc16is7xx_i2c.c
> +++ b/drivers/tty/serial/sc16is7xx_i2c.c
> @@ -21,6 +21,8 @@ static int sc16is7xx_i2c_probe(struct i2c_client *i2c)
> if (!devtype)
> return dev_err_probe(&i2c->dev, -ENODEV, "Failed to match device\n");
>
> + sc16is7xx_setup_reset_pin(&i2c->dev);
Move this call inside sc16is7xx_probe() function, since it is common to
both i2c and spi interfaces. Also, you will see in sc16is7xx_probe()
that we already issue a software reset. If you
specify a hardware reset pin, then you shouldn't issue the software
reset.
> +
> memcpy(®cfg, &sc16is7xx_regcfg, sizeof(struct regmap_config));
>
> for (i = 0; i < devtype->nr_uart; i++) {
> diff --git a/drivers/tty/serial/sc16is7xx_spi.c b/drivers/tty/serial/sc16is7xx_spi.c
> index 73df36f8a7fd..ce38561faaf0 100644
> --- a/drivers/tty/serial/sc16is7xx_spi.c
> +++ b/drivers/tty/serial/sc16is7xx_spi.c
> @@ -38,6 +38,8 @@ static int sc16is7xx_spi_probe(struct spi_device *spi)
> if (!devtype)
> return dev_err_probe(&spi->dev, -ENODEV, "Failed to match device\n");
>
> + sc16is7xx_setup_reset_pin(&spi->dev);
> +
> memcpy(®cfg, &sc16is7xx_regcfg, sizeof(struct regmap_config));
>
> for (i = 0; i < devtype->nr_uart; i++) {
> --
> 2.34.1
>
>
>
--
Hugo Villeneuve
