On Tue, 4 Jun 2024 21:27:26 +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 chip reset. If the reset-gpios is
> defined in the dt, do the hard reset through this gpio, othwerwise do
> the soft reset as before.
>
> Reviewed-by: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>
I never gave you permission to add this tag, remove it. Make sure you
fully understand the meaning of tags by reading patches submission
guidelines.
> Signed-off-by: Hui Wang <hui.wang@xxxxxxxxxxxxx>
> ---
> In the v2:
> - move the soft reset and hard reset into one fucntion
> - move the reset function to sc16is7xx.c and call it in _probe()
> - add udelay(5) before deasserting the gpio reset pin
>
> drivers/tty/serial/sc16is7xx.c | 28 ++++++++++++++++++++++++----
> 1 file changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
> index bf0065d1c8e9..119abfb4607c 100644
> --- a/drivers/tty/serial/sc16is7xx.c
> +++ b/drivers/tty/serial/sc16is7xx.c
> @@ -14,6 +14,7 @@
> #include <linux/delay.h>
> #include <linux/device.h>
> #include <linux/export.h>
> +#include <linux/gpio/consumer.h>
> #include <linux/gpio/driver.h>
> #include <linux/idr.h>
> #include <linux/kthread.h>
> @@ -1467,6 +1468,25 @@ static const struct serial_rs485 sc16is7xx_rs485_supported = {
> .delay_rts_after_send = 1, /* Not supported but keep returning -EINVAL */
> };
>
Add function description from original comment "Reset device,
purging any pending irq / data", since the comment applies to both
hardware and software reset,
> +static int sc16is7xx_reset(struct device *dev, struct regmap *regmaps[])
Simply pass "struct regmap *regmap" as the second argument. See
sc16is7xx_setup_mctrl_ports() for example.
> +{
> + struct gpio_desc *reset_gpiod;
reset_gpiod -> reset_gpio
> +
> + reset_gpiod = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
> + if (!reset_gpiod)
Follow Andy's suggestion here.
> + /* soft reset device, purging any pending irq / data */
"Software reset".
> + regmap_write(regmaps[0], SC16IS7XX_IOCONTROL_REG,
> + SC16IS7XX_IOCONTROL_SRESET_BIT);
> + else if (!IS_ERR(reset_gpiod)) {
> + /* delay 5 us (at least 3 us) and deassert the gpio to exit the hard reset */
You can omit the "delay 5 us" since it is obvious from the code. Maybe
add that "The minimum reset pulse width is 3 us" as stated in the
datasheet.
As a general note for your comments: capitalize the first letter,
ex: "Deassert GPIO" and not "deassert GPIO".
> + udelay(5);
> + gpiod_set_value_cansleep(reset_gpiod, 0);
Move the comment "deassert the gpio to exit the hard reset" here. You
could also simplify it as "Deassert GPIO.".
> + } else
> + return PTR_ERR(reset_gpiod);
return dev_err_probe(dev, PTR_ERR(reset_gpiod), "Failed to get reset
GPIO\n");
> +
> + return 0;
> +}
> +
> int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
> struct regmap *regmaps[], int irq)
> {
> @@ -1527,6 +1547,10 @@ int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
> s->devtype = devtype;
> dev_set_drvdata(dev, s);
>
> + ret = sc16is7xx_reset(dev, regmaps);
> + if (ret)
> + goto out_clk;
> +
> kthread_init_worker(&s->kworker);
> s->kworker_task = kthread_run(kthread_worker_fn, &s->kworker,
> "sc16is7xx");
> @@ -1536,10 +1560,6 @@ int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
> }
> sched_set_fifo(s->kworker_task);
>
> - /* reset device, purging any pending irq / data */
> - regmap_write(regmaps[0], SC16IS7XX_IOCONTROL_REG,
> - SC16IS7XX_IOCONTROL_SRESET_BIT);
> -
> /* Mark each port line and status as uninitialised. */
> for (i = 0; i < devtype->nr_uart; ++i) {
> s->p[i].port.line = SC16IS7XX_MAX_DEVS;
> --
> 2.34.1
>
>
>
--
Hugo Villeneuve
