i2c: mux: pca954x: support property idle-state

This supports property idle-state,if present,
overrides i2c-mux-idle-disconnect.

My use cases:
	- Use the property idle-state to fix
	  an errata on LS2085ARDB and LS2088ARDB.
	- Errata id: E-00013(board LS2085ARDB and
	  LS2088ARDB revision on Rev.B, Rev.C and Rev.D).
	- About E-00013:
	  - Description: I2C1 and I2C3 buses
	    are missing pull-up.
	  - Impact: When the PCA954x device is tri-stated, the I2C bus
	    will float. This makes the I2C bus and its associated
	    downstream devices inaccessible.
	  - Hardware fix: Populate resistors R189 and R190 for I2C1
	    and resistors R228 and R229 for I2C3.
	  - Software fix: Remove the tri-state option from the PCA954x
	    driver(PCA954x always on enable status, specify a
	    channel zero in dts to fix the errata E-00013).

Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Biwen Li <biwen.li@nxp.com>
Signed-off-by: Peter Rosin <peda@axentia.se>

diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index 923aa3a..a0d926a 100644 (file)
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -86,7 +86,7 @@ struct pca954x {
 
        u8 last_chan;           /* last register value */
        /* MUX_IDLE_AS_IS, MUX_IDLE_DISCONNECT or >= 0 for channel */
-       s8 idle_state;
+       s32 idle_state;
 
        struct i2c_client *client;
 
@@ -229,20 +229,23 @@ static int pca954x_reg_write(struct i2c_adapter *adap,
                                I2C_SMBUS_BYTE, &dummy);
 }
 
+static u8 pca954x_regval(struct pca954x *data, u8 chan)
+{
+       /* We make switches look like muxes, not sure how to be smarter. */
+       if (data->chip->muxtype == pca954x_ismux)
+               return chan | data->chip->enable;
+       else
+               return 1 << chan;
+}
+
 static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan)
 {
        struct pca954x *data = i2c_mux_priv(muxc);
        struct i2c_client *client = data->client;
-       const struct chip_desc *chip = data->chip;
        u8 regval;
        int ret = 0;
 
-       /* we make switches look like muxes, not sure how to be smarter */
-       if (chip->muxtype == pca954x_ismux)
-               regval = chan | chip->enable;
-       else
-               regval = 1 << chan;
-
+       regval = pca954x_regval(data, chan);
        /* Only select the channel if its different from the last channel */
        if (data->last_chan != regval) {
                ret = pca954x_reg_write(muxc->parent, client, regval);
@@ -256,7 +259,7 @@ static int pca954x_deselect_mux(struct i2c_mux_core *muxc, u32 chan)
 {
        struct pca954x *data = i2c_mux_priv(muxc);
        struct i2c_client *client = data->client;
-       s8 idle_state;
+       s32 idle_state;
 
        idle_state = READ_ONCE(data->idle_state);
        if (idle_state >= 0)
@@ -402,6 +405,22 @@ static void pca954x_cleanup(struct i2c_mux_core *muxc)
        i2c_mux_del_adapters(muxc);
 }
 
+static int pca954x_init(struct i2c_client *client, struct pca954x *data)
+{
+       int ret;
+
+       if (data->idle_state >= 0)
+               data->last_chan = pca954x_regval(data, data->idle_state);
+       else
+               data->last_chan = 0; /* Disconnect multiplexer */
+
+       ret = i2c_smbus_write_byte(client, data->last_chan);
+       if (ret < 0)
+               data->last_chan = 0;
+
+       return ret;
+}
+
 /*
  * I2C init/probing/exit functions
  */
@@ -411,7 +430,6 @@ static int pca954x_probe(struct i2c_client *client,
        struct i2c_adapter *adap = client->adapter;
        struct device *dev = &client->dev;
        struct device_node *np = dev->of_node;
-       bool idle_disconnect_dt;
        struct gpio_desc *gpio;
        struct i2c_mux_core *muxc;
        struct pca954x *data;
@@ -462,23 +480,24 @@ static int pca954x_probe(struct i2c_client *client,
                }
        }
 
-       /* Write the mux register at addr to verify
+       data->idle_state = MUX_IDLE_AS_IS;
+       if (of_property_read_u32(np, "idle-state", &data->idle_state)) {
+               if (np && of_property_read_bool(np, "i2c-mux-idle-disconnect"))
+                       data->idle_state = MUX_IDLE_DISCONNECT;
+       }
+
+       /*
+        * Write the mux register at addr to verify
         * that the mux is in fact present. This also
-        * initializes the mux to disconnected state.
+        * initializes the mux to a channel
+        * or disconnected state.
         */
-       if (i2c_smbus_write_byte(client, 0) < 0) {
+       ret = pca954x_init(client, data);
+       if (ret < 0) {
                dev_warn(dev, "probe failed\n");
                return -ENODEV;
        }
 
-       data->last_chan = 0;               /* force the first selection */
-       data->idle_state = MUX_IDLE_AS_IS;
-
-       idle_disconnect_dt = np &&
-               of_property_read_bool(np, "i2c-mux-idle-disconnect");
-       if (idle_disconnect_dt)
-               data->idle_state = MUX_IDLE_DISCONNECT;
-
        ret = pca954x_irq_setup(muxc);
        if (ret)
                goto fail_cleanup;
@@ -530,9 +549,13 @@ static int pca954x_resume(struct device *dev)
        struct i2c_client *client = to_i2c_client(dev);
        struct i2c_mux_core *muxc = i2c_get_clientdata(client);
        struct pca954x *data = i2c_mux_priv(muxc);
+       int ret;
 
-       data->last_chan = 0;
-       return i2c_smbus_write_byte(client, 0);
+       ret = pca954x_init(client, data);
+       if (ret < 0)
+               dev_err(&client->dev, "failed to verify mux presence\n");
+
+       return ret;
 }
 #endif