overlays: i2c-mux: Add 'base' parameter

Add a 'base' parameter to set an explicit bus number for the channels,
where the requested bus number is base + channel ID.

Signed-off-by: Phil Elwell <[email protected]>

Author: pelwell

arch/arm/boot/dts/overlays/README

@@ -2026,6 +2026,9 @@ Params: pca9542                 Select the NXP PCA9542 device
 
         addr                    Change I2C address of the device (default 0x70)
 
+        base                    Set an explicit base value for the channel bus
+                                numbers
+
         i2c0                    Choose the I2C0 bus on GPIOs 0&1
 
         i2c_csi_dsi             Choose the I2C0 bus on GPIOs 44&45

arch/arm/boot/dts/overlays/i2c-mux-overlay.dts

@@ -159,6 +159,10 @@
 			<&pca9545>,"reg:0",
 			<&pca9548>,"reg:0";
 
+		base =  <&pca9542>,"base-nr:0",
+			<&pca9545>,"base-nr:0",
+			<&pca9548>,"base-nr:0";
+
 		i2c0 = <&frag100>, "target:0=",<&i2c0>,
 			      <0>,"+101+102";
 		i2c_csi_dsi = <&frag100>, "target:0=",<&i2c_csi_dsi>,

drivers/i2c/i2c-mux.c

@@ -360,7 +360,7 @@ int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
 
 		of_property_read_u32(dev_node, "base-nr", &base_nr);
 		if (!force_nr)
-			force_nr = base_nr;
+			force_nr = base_nr + chan_id;
 
 		if (muxc->arbitrator)
 			mux_node = of_get_child_by_name(dev_node, "i2c-arb");