Some boards connect a GPIO to the reset pin, and the reset pin needs
to be setup correctly before accessing the chip.
Add a function to handle the chip reset. If the reset-gpios is defined
in the DT, do hardware reset through this GPIO, othwerwise do software
reset as before.
Signed-off-by: Hui Wang <hui.wang@xxxxxxxxxxxxx>
---
In the v4:
- Move sc16is7xx_reset(dev, regmaps[0]) to the where software reset was located
- Move /* Deassert GPIO */ to the end of corresponding statement
- Change the comment before reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH)
- Change udelay(5) to usleep_range(5, 10)
drivers/tty/serial/sc16is7xx.c | 34 +++++++++++++++++++++++++++++++---
1 file changed, 31 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index bf0065d1c8e9..a67c4eda0c03 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 +1468,32 @@ static const struct serial_rs485 sc16is7xx_rs485_supported = {
.delay_rts_after_send = 1, /* Not supported but keep returning -EINVAL */
};
+/* Reset device, purging any pending irq / data */
+static int sc16is7xx_reset(struct device *dev, struct regmap *regmap)
+{
+ struct gpio_desc *reset_gpio;
+
+ /*
+ * The reset input is active low, and flag GPIOD_OUT_HIGH ensures the
+ * GPIO is low once devm_gpiod_get_optional returns a valid gpio_desc.
+ */
+ reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+ if (IS_ERR(reset_gpio))
+ return dev_err_probe(dev, PTR_ERR(reset_gpio), "Failed to get reset GPIO\n");
+
+ if (reset_gpio) {
+ /* The minimum reset pulse width is 3 us. */
+ usleep_range(5, 10);
+ gpiod_set_value_cansleep(reset_gpio, 0); /* Deassert GPIO */
+ } else {
+ /* Software reset */
+ regmap_write(regmap, SC16IS7XX_IOCONTROL_REG,
+ SC16IS7XX_IOCONTROL_SRESET_BIT);
+ }
+
+ return 0;
+}
+
int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
struct regmap *regmaps[], int irq)
{
@@ -1536,9 +1563,9 @@ 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);
+ ret = sc16is7xx_reset(dev, regmaps[0]);
+ if (ret)
+ goto out_kthread;
/* Mark each port line and status as uninitialised. */
for (i = 0; i < devtype->nr_uart; ++i) {
@@ -1663,6 +1690,7 @@ int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
uart_remove_one_port(&sc16is7xx_uart, &s->p[i].port);
}
+out_kthread:
kthread_stop(s->kworker_task);
out_clk:
--
2.34.1
