ALSA: oxygen: Xonar DG(X): fix Stereo Upmixing regression

The code introduced in commit 1f91ecc1 ("ALSA: oxygen: modify
adjust_dg_dac_routing function") accidentally disregarded the old value
of the playback routing register, so it broke the "Stereo Upmixing"
mixer control.

The unmuted parts of the channel routing are the same for all settings
of the output destination, so it suffices to revert that part of the
patch.

Fixes: 1f91ecc1 ('ALSA: oxygen: modify adjust_dg_dac_routing function')
Tested-by: Roman Volkov <v1ron@mail.ru>
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/oxygen/xonar_dg.c

@@ -238,11 +238,21 @@ void set_cs4245_adc_params(struct oxygen *chip,
 	cs4245_write_spi(chip, CS4245_MCLK_FREQ);
 }
 
+static inline unsigned int shift_bits(unsigned int value,
+				      unsigned int shift_from,
+				      unsigned int shift_to,
+				      unsigned int mask)
+{
+	if (shift_from < shift_to)
+		return (value << (shift_to - shift_from)) & mask;
+	else
+		return (value >> (shift_from - shift_to)) & mask;
+}
+
 unsigned int adjust_dg_dac_routing(struct oxygen *chip,
 					  unsigned int play_routing)
 {
 	struct dg *data = chip->model_data;
-	unsigned int routing = 0;
 
 	switch (data->output_sel) {
 	case PLAYBACK_DST_HP:
@@ -252,15 +262,23 @@ unsigned int adjust_dg_dac_routing(struct oxygen *chip,
 			OXYGEN_PLAY_MUTE67, OXYGEN_PLAY_MUTE_MASK);
 		break;
 	case PLAYBACK_DST_MULTICH:
-		routing = (0 << OXYGEN_PLAY_DAC0_SOURCE_SHIFT) |
-			  (2 << OXYGEN_PLAY_DAC1_SOURCE_SHIFT) |
-			  (1 << OXYGEN_PLAY_DAC2_SOURCE_SHIFT) |
-			  (0 << OXYGEN_PLAY_DAC3_SOURCE_SHIFT);
 		oxygen_write8_masked(chip, OXYGEN_PLAY_ROUTING,
 			OXYGEN_PLAY_MUTE01, OXYGEN_PLAY_MUTE_MASK);
 		break;
 	}
-	return routing;
+	return (play_routing & OXYGEN_PLAY_DAC0_SOURCE_MASK) |
+	       shift_bits(play_routing,
+			  OXYGEN_PLAY_DAC2_SOURCE_SHIFT,
+			  OXYGEN_PLAY_DAC1_SOURCE_SHIFT,
+			  OXYGEN_PLAY_DAC1_SOURCE_MASK) |
+	       shift_bits(play_routing,
+			  OXYGEN_PLAY_DAC1_SOURCE_SHIFT,
+			  OXYGEN_PLAY_DAC2_SOURCE_SHIFT,
+			  OXYGEN_PLAY_DAC2_SOURCE_MASK) |
+	       shift_bits(play_routing,
+			  OXYGEN_PLAY_DAC0_SOURCE_SHIFT,
+			  OXYGEN_PLAY_DAC3_SOURCE_SHIFT,
+			  OXYGEN_PLAY_DAC3_SOURCE_MASK);
 }
 
 void dump_cs4245_registers(struct oxygen *chip,