i2c: mux: mlxcpld: fix i2c mux selection caching

smbus functions return -ve on error, 0 on success.  However,
__i2c_transfer() have a different return signature - -ve on error, or
number of buffers transferred (which may be zero or greater).

The upshot of this is that the sense of the test is reversed when using
the mux on a bus supporting the master_xfer method: we cache the value
and never retry if we fail to transfer any buffers, but if we succeed,
we clear the cached value.

Fix this by making mlxcpld_mux_reg_write() return a -ve error code for
all failure cases, just as was done in commit 7f638c1cb0a1 ("i2c: mux:
pca954x: fix i2c mux selection caching").

This also aligns the implementations of these two muxes in this area.

Signed-off-by: Peter Rosin <peda@axentia.se>
Acked-by: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

1 files changed, 13 insertions, 11 deletions

diff --git a/drivers/i2c/muxes/i2c-mux-mlxcpld.c b/drivers/i2c/muxes/i2c-mux-mlxcpld.c
index 3ab654bbfab5..b7ca249ec9c3 100644
--- a/drivers/i2c/muxes/i2c-mux-mlxcpld.c
+++ b/drivers/i2c/muxes/i2c-mux-mlxcpld.c
@@ -95,6 +95,7 @@ static int mlxcpld_mux_reg_write(struct i2c_adapter *adap,
                                  struct i2c_client *client, u8 val)
 {
         struct mlxcpld_mux_plat_data *pdata = dev_get_platdata(&client->dev);
+        int ret = -ENODEV;
 
         if (adap->algo->master_xfer) {
                 struct i2c_msg msg;
@@ -104,17 +105,21 @@ static int mlxcpld_mux_reg_write(struct i2c_adapter *adap,
                 msg.flags = 0;
                 msg.len = 2;
                 msg.buf = msgbuf;
-                return __i2c_transfer(adap, &msg, 1);
+                ret = __i2c_transfer(adap, &msg, 1);
+
+                if (ret >= 0 && ret != 1)
+                        ret = -EREMOTEIO;
         } else if (adap->algo->smbus_xfer) {
                 union i2c_smbus_data data;
 
                 data.byte = val;
-                return adap->algo->smbus_xfer(adap, client->addr,
-                                              client->flags, I2C_SMBUS_WRITE,
-                                              pdata->sel_reg_addr,
-                                              I2C_SMBUS_BYTE_DATA, &data);
-        } else
-                return -ENODEV;
+                ret = adap->algo->smbus_xfer(adap, client->addr,
+                                             client->flags, I2C_SMBUS_WRITE,
+                                             pdata->sel_reg_addr,
+                                             I2C_SMBUS_BYTE_DATA, &data);
+        }
+
+        return ret;
 }
 
 static int mlxcpld_mux_select_chan(struct i2c_mux_core *muxc, u32 chan)
@@ -127,10 +132,7 @@ static int mlxcpld_mux_select_chan(struct i2c_mux_core *muxc, u32 chan)
         /* Only select the channel if its different from the last channel */
         if (data->last_chan != regval) {
                 err = mlxcpld_mux_reg_write(muxc->parent, client, regval);
-                if (err)
-                        data->last_chan = 0;
-                else
-                        data->last_chan = regval;
+                data->last_chan = err < 0 ? 0 : regval;
         }
 
         return err;