On some Layerscape boards like LS2085ARDB and LS2088ARDB,
input pull-up resistors on PCA954x MUX device are missing on board,
So, if MUX are disabled after powered-on, input lines will float
leading to incorrect functionality.
Hence, PCA954x MUX device should never be turned-off after
power-on.
Add property to skip disabling PCA954x MUX device
if device tree contains "i2c-mux-never-disable"
for PCA954x device node.
Errata ID: E-00013 on board LS2085ARDB and LS2088ARDB
(Board revision found on Rev.B, Rev.C and Rev.D)
Signed-off-by: Biwen Li <biwen.li@xxxxxxx>
---
drivers/i2c/muxes/i2c-mux-pca954x.c | 33 +++++++++++++++++++++++++----
1 file changed, 29 insertions(+), 4 deletions(-)
diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index 923aa3a5a3dc..ea8aca54d572 100644
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -93,6 +93,7 @@ struct pca954x {
struct irq_domain *irq;
unsigned int irq_mask;
raw_spinlock_t lock;
+ u8 disable_mux; /* do not disable mux if val not 0 */
};
/* Provide specs for the PCA954x types we know about */
@@ -258,6 +259,11 @@ static int pca954x_deselect_mux(struct i2c_mux_core *muxc, u32 chan)
struct i2c_client *client = data->client;
s8 idle_state;
+ if (data->disable_mux != 0) {
+ data->last_chan = data->chip->nchans;
+ return pca954x_reg_write(muxc->parent, client, data->disable_mux);
+ }
+
idle_state = READ_ONCE(data->idle_state);
if (idle_state >= 0)
/* Set the mux back to a predetermined channel */
@@ -462,16 +468,32 @@ static int pca954x_probe(struct i2c_client *client,
}
}
+ /* Errata ID E-00013 on board LS2088ARDB and LS2088ARDB:
+ * The point here is that you must not disable a mux if there
+ * are no pullups on the input or you mess up the I2C. This
+ * needs to be put into the DTS really as the kernel cannot
+ * know this otherwise.
+ */
+
+ data->disable_mux = np &&
+ of_property_read_bool(np, "i2c-mux-never-disable") &&
+ data->chip->muxtype == pca954x_ismux ?
+ data->chip->enable : 0;
+
/* Write the mux register at addr to verify
* that the mux is in fact present. This also
* initializes the mux to disconnected state.
*/
- if (i2c_smbus_write_byte(client, 0) < 0) {
+ if (i2c_smbus_write_byte(client, data->disable_mux) < 0) {
dev_warn(dev, "probe failed\n");
return -ENODEV;
}
- data->last_chan = 0; /* force the first selection */
+ if (data->disable_mux != 0)
+ data->last_chan = data->chip->nchans;
+ else
+ data->last_chan = 0; /* force the first selection */
+
data->idle_state = MUX_IDLE_AS_IS;
idle_disconnect_dt = np &&
@@ -531,8 +553,11 @@ static int pca954x_resume(struct device *dev)
struct i2c_mux_core *muxc = i2c_get_clientdata(client);
struct pca954x *data = i2c_mux_priv(muxc);
- data->last_chan = 0;
- return i2c_smbus_write_byte(client, 0);
+ if (data->disable_mux != 0)
+ data->last_chan = data->chip->nchans;
+ else
+ data->last_chan = 0;
+ return i2c_smbus_write_byte(client, data->disable_mux);
}
#endif
--
2.17.1
