ASoC: rt5663: Add the function of impedance sensing

Support the function of impedance sensing. It could be set the matrix row
number of the impedance sensing table and the related parameters in the
DTS.
Signed-off-by: Oder Chiou <oder_chiou@realtek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/rt5663.txt

@@ -19,6 +19,22 @@ Optional properties:
   Based on the different PCB layout, add the manual offset value to
   compensate the DC offset for each L and R channel, and they are different
   between headphone and headset.
+- "realtek,impedance_sensing_num"
+  The matrix row number of the impedance sensing table.
+  If the value is 0, it means the impedance sensing is not supported.
+- "realtek,impedance_sensing_table"
+  The matrix rows of the impedance sensing table are consisted by impedance
+  minimum, impedance maximun, volume, DC offset w/o and w/ mic of each L and
+  R channel accordingly. Example is shown as following.
+  <   0    300  7  0xffd160  0xffd1c0  0xff8a10  0xff8ab0
+    301  65535  4  0xffe470  0xffe470  0xffb8e0  0xffb8e0>
+  The first and second column are defined for the impedance range. If the
+  detected impedance value is in the range, then the volume value of the
+  third column will be set to codec. In our codec design, each volume value
+  should compensate different DC offset to avoid the pop sound, and it is
+  also different between headphone and headset. In the example, the
+  "realtek,impedance_sensing_num" is 2. It means that there are 2 ranges of
+  impedance in the impedance sensing function.
 
 Pins on the device (for linking into audio routes) for RT5663:
 

include/sound/rt5663.h

@@ -16,6 +16,9 @@ struct rt5663_platform_data {
 	unsigned int dc_offset_r_manual;
 	unsigned int dc_offset_l_manual_mic;
 	unsigned int dc_offset_r_manual_mic;
+
+	unsigned int impedance_sensing_num;
+	unsigned int *impedance_sensing_table;
 };
 
 #endif