i2c: mux: gpio: Add support for the 'settle-time-us' property

Some hardware need some time to switch from a bus to another. This can
cause the first transfers following the selection of a bus to fail.
There is no way to configure this kind of waiting time in the driver.

Add support for the 'settle-time-us' device-tree property. When set,
the i2c_mux_gpio_select() applies a delay before returning, leaving
enough time to the hardware to switch to the new bus.

Signed-off-by: Bastien Curutchet <bastien.curutchet@bootlin.com>
Reviewed-by: Andi Shyti <andi.shyti@kernel.org>
Acked-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>

diff --git a/drivers/i2c/muxes/i2c-mux-gpio.c b/drivers/i2c/muxes/i2c-mux-gpio.c
index c61e9d9ea695499668d29f9ce405f4f9d5e4d400..944577bb09c178ec46cf4ff5e57394012a0f9ea8 100644 (file)
--- a/drivers/i2c/muxes/i2c-mux-gpio.c
+++ b/drivers/i2c/muxes/i2c-mux-gpio.c
@@ -6,6 +6,7 @@
  */
 
 #include <linux/bits.h>
+#include <linux/delay.h>
 #include <linux/gpio/consumer.h>
 #include <linux/gpio/driver.h>
 #include <linux/i2c.h>
@@ -37,6 +38,9 @@ static int i2c_mux_gpio_select(struct i2c_mux_core *muxc, u32 chan)
 
        i2c_mux_gpio_set(mux, chan);
 
+       if (mux->data.settle_time)
+               fsleep(mux->data.settle_time);
+
        return 0;
 }
 
@@ -116,6 +120,8 @@ static int i2c_mux_gpio_probe_fw(struct gpiomux *mux,
        if (device_property_read_u32(dev, "idle-state", &mux->data.idle))
                mux->data.idle = I2C_MUX_GPIO_NO_IDLE;
 
+       device_property_read_u32(dev, "settle-time-us", &mux->data.settle_time);
+
        return 0;
 }
 

diff --git a/include/linux/platform_data/i2c-mux-gpio.h b/include/linux/platform_data/i2c-mux-gpio.h
index 816a4cd3ccb5559d82291687bc448690f76dae8b..96843aab4d1e2bf1ca6da06e3e352643f026034d 100644 (file)
--- a/include/linux/platform_data/i2c-mux-gpio.h
+++ b/include/linux/platform_data/i2c-mux-gpio.h
@@ -19,6 +19,7 @@
  *     position
  * @n_values: Number of multiplexer positions (busses to instantiate)
  * @idle: Bitmask to write to MUX when idle or GPIO_I2CMUX_NO_IDLE if not used
+ * @settle_time: Delay to wait when a new bus is selected
  */
 struct i2c_mux_gpio_platform_data {
        int parent;
@@ -26,6 +27,7 @@ struct i2c_mux_gpio_platform_data {
        const unsigned *values;
        int n_values;
        unsigned idle;
+       u32 settle_time;
 };
 
 #endif /* _LINUX_I2C_MUX_GPIO_H */