| Message ID | 20240529091739.10808-4-bastien.curutchet@bootlin.com |
|---|---|
| State | New |
| Headers | show |
| Series | i2c: mux: gpio: Add 'transition-delay-us' property | expand |
Hi! 2024-05-29 at 11:17, Bastien Curutchet wrote: > 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 'transition-delay-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> > --- > drivers/i2c/muxes/i2c-mux-gpio.c | 6 ++++++ > include/linux/platform_data/i2c-mux-gpio.h | 2 ++ > 2 files changed, 8 insertions(+) > > diff --git a/drivers/i2c/muxes/i2c-mux-gpio.c b/drivers/i2c/muxes/i2c-mux-gpio.c > index c61e9d9ea695..b9cfc80660e2 100644 > --- 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.transition_delay) > + udelay(mux->data.transition_delay); fsleep() is appropriate here. Cheers, Peter
diff --git a/drivers/i2c/muxes/i2c-mux-gpio.c b/drivers/i2c/muxes/i2c-mux-gpio.c index c61e9d9ea695..b9cfc80660e2 100644 --- 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.transition_delay) + udelay(mux->data.transition_delay); + 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, "transition-delay-us", &mux->data.transition_delay); + return 0; } diff --git a/include/linux/platform_data/i2c-mux-gpio.h b/include/linux/platform_data/i2c-mux-gpio.h index 816a4cd3ccb5..c449f714d32b 100644 --- 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 + * @transition_delay: 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; + int transition_delay; }; #endif /* _LINUX_I2C_MUX_GPIO_H */
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 'transition-delay-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> --- drivers/i2c/muxes/i2c-mux-gpio.c | 6 ++++++ include/linux/platform_data/i2c-mux-gpio.h | 2 ++ 2 files changed, 8 insertions(+)