From: Wojciech Siudy <wojciech.siudy@xxxxxxxxx>
Channel selection that has timed out is a symptom of mux'es I2C
subsystem failure. Without sending reset pulse the power-on-reset
of entire device would be needed to restore the communication.
The datasheet mentions 4 ns as a minimal hold time of reset pulse,
but due to paths capacity and mux having its own clock it is better
to have it about 1 us.
Signed-off-by: Wojciech Siudy <wojciech.siudy@xxxxxxxxx>
---
Changelog:
v2:
* Removed mail header from the commit log
* Decreased reset pulse hold time from 10 to 1 us
---
drivers/i2c/muxes/i2c-mux-pca954x.c | 30 +++++++++++++++++++++--------
1 file changed, 22 insertions(+), 8 deletions(-)
diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index 6f8401825..e09d4d107 100644
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -316,6 +316,22 @@ static u8 pca954x_regval(struct pca954x *data, u8 chan)
return 1 << chan;
}
+static void pca954x_reset_deassert(struct pca954x *data)
+{
+ if (data->reset_cont)
+ reset_control_deassert(data->reset_cont);
+ else
+ gpiod_set_value_cansleep(data->reset_gpio, 0);
+}
+
+static void pca954x_reset_assert(struct pca954x *data)
+{
+ if (data->reset_cont)
+ reset_control_assert(data->reset_cont);
+ else
+ gpiod_set_value_cansleep(data->reset_gpio, 1);
+}
+
static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan)
{
struct pca954x *data = i2c_mux_priv(muxc);
@@ -329,6 +345,12 @@ static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan)
ret = pca954x_reg_write(muxc->parent, client, regval);
data->last_chan = ret < 0 ? 0 : regval;
}
+ if (ret == -ETIMEDOUT && (data->reset_cont || data->reset_gpio)) {
+ dev_warn(&client->dev, "channel select failed, resetting...\n");
+ pca954x_reset_assert(data);
+ udelay(1);
+ pca954x_reset_deassert(data);
+ }
return ret;
}
@@ -543,14 +565,6 @@ static int pca954x_get_reset(struct device *dev, struct pca954x *data)
return 0;
}
-static void pca954x_reset_deassert(struct pca954x *data)
-{
- if (data->reset_cont)
- reset_control_deassert(data->reset_cont);
- else
- gpiod_set_value_cansleep(data->reset_gpio, 0);
-}
-
/*
* I2C init/probing/exit functions
*/
--
2.34.1
