ASoC: Support second DC servo readback method for wm_hubs

More recent Wolfson hubs devices add the ability to read back the DC
servo calibration information from the register used to write offsets,
and later still ones remove the old readback registers. Add support
for the new scheme, and use it for WM8994 device revisions that
support it.
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>

sound/soc/codecs/wm8994.c

@@ -3730,11 +3730,12 @@ static int wm8994_codec_probe(struct platform_device *pdev)
 	case 3:
 		wm8994->hubs.dcs_codes = -5;
 		wm8994->hubs.hp_startup_mode = 1;
+		wm8994->hubs.dcs_readback_mode = 1;
 		break;
 	default:
+		wm8994->hubs.dcs_readback_mode = 1;
 		break;
 	}
-			   
 
 	/* Remember if AIFnLRCLK is configured as a GPIO.  This should be
 	 * configured on init - if a system wants to do this dynamically

sound/soc/codecs/wm_hubs.c

@@ -86,7 +86,7 @@ static void wait_for_dc_servo(struct snd_soc_codec *codec)
 static void calibrate_dc_servo(struct snd_soc_codec *codec)
 {
 	struct wm_hubs_data *hubs = codec->private_data;
-	u16 reg, dcs_cfg;
+	u16 reg, reg_l, reg_r, dcs_cfg;
 
 	/* Set for 32 series updates */
 	snd_soc_update_bits(codec, WM8993_DC_SERVO_1,
@@ -110,19 +110,38 @@ static void calibrate_dc_servo(struct snd_soc_codec *codec)
 		dev_dbg(codec->dev, "Applying %d code DC servo correction\n",
 			hubs->dcs_codes);
 
+		/* Different chips in the family support different
+		 * readback methods.
+		 */
+		switch (hubs->dcs_readback_mode) {
+		case 0:
+			reg_l = snd_soc_read(codec, WM8993_DC_SERVO_READBACK_1)
+				& WM8993_DCS_INTEG_CHAN_0_MASK;;
+			reg_r = snd_soc_read(codec, WM8993_DC_SERVO_READBACK_2)
+				& WM8993_DCS_INTEG_CHAN_1_MASK;
+			break;
+		case 1:
+			reg = snd_soc_read(codec, WM8993_DC_SERVO_3);
+			reg_l = (reg & WM8993_DCS_DAC_WR_VAL_1_MASK)
+				>> WM8993_DCS_DAC_WR_VAL_1_SHIFT;
+			reg_r = reg & WM8993_DCS_DAC_WR_VAL_0_MASK;
+			break;
+		default:
+			WARN(1, "Unknown DCS readback method");
+			break;
+		}
+
 		/* HPOUT1L */
-		reg = snd_soc_read(codec, WM8993_DC_SERVO_READBACK_1) &
-			WM8993_DCS_INTEG_CHAN_0_MASK;;
-		if (reg + hubs->dcs_codes > 0 && reg + hubs->dcs_codes < 0xff)
-			reg += hubs->dcs_codes;
-		dcs_cfg = reg << WM8993_DCS_DAC_WR_VAL_1_SHIFT;
+		if (reg_l + hubs->dcs_codes > 0 &&
+		    reg_l + hubs->dcs_codes < 0xff)
+			reg_l += hubs->dcs_codes;
+		dcs_cfg = reg_l << WM8993_DCS_DAC_WR_VAL_1_SHIFT;
 
 		/* HPOUT1R */
-		reg = snd_soc_read(codec, WM8993_DC_SERVO_READBACK_2) &
-			WM8993_DCS_INTEG_CHAN_1_MASK;
-		if (reg + hubs->dcs_codes > 0 && reg + hubs->dcs_codes < 0xff)
-			reg += hubs->dcs_codes;
-		dcs_cfg |= reg;
+		if (reg_r + hubs->dcs_codes > 0 &&
+		    reg_r + hubs->dcs_codes < 0xff)
+			reg_r += hubs->dcs_codes;
+		dcs_cfg |= reg_r;
 
 		/* Do it */
 		snd_soc_write(codec, WM8993_DC_SERVO_3, dcs_cfg);

sound/soc/codecs/wm_hubs.h

@@ -21,6 +21,7 @@ extern const unsigned int wm_hubs_spkmix_tlv[];
 /* This *must* be the first element of the codec->private_data struct */
 struct wm_hubs_data {
 	int dcs_codes;
+	int dcs_readback_mode;
 	int hp_startup_mode;
 };