--- ac97_codec.c	Thu Dec 04 15:53:12 2003

+++ linux-2.4.23/drivers/sound/ac97_codec.c	Thu Dec 04 16:30:08 2003

@@ -30,6 +30,9 @@

  **************************************************************************

  *

  * History

+ * Dec 04, 2003 Dennis Newbold <dennisn@pe.net>

+ *   Added logic to use the MICBOOST bit when writing or reading the

+ *   SOUND_MIXER_MIC channel.

  * May 02, 2003 Liam Girdwood <liam.girdwood@wolfsonmicro.com>

  *	Removed non existant WM9700

  *	Added support for WM9705, WM9708, WM9709, WM9710, WM9711

@@ -240,6 +243,26 @@

 	{-1,0}

 };

 

+/* Note that scale for SOUND_MIXER_MIC is set to 46 rather than 32.  This is

+ * to include the lower volume DB values that do not use the AC97_MICBOOST

+ * bit.  There is a small glitch in the scaling in that the last value to use

+ * the boost bit is 31, which translates to -14.5 dB, and the next lower value,

+ * which does not use the boost bit is 32, which is converted to 18, which

+ * translates to -15 dB, a difference of only 0.5 dB.  All other gain values

+ *  differ by 1.5 dB.  This is considered acceptable because it happens only

+ *  at an extremely low volume, which most users will not be interested in.

+ *  -dln- */

+

+/* MIC_NATURAL_SCALE is the no. of different gain settings that will fit in

+ * the MIC Volume Gain Register.  Computed gain values which fall within this

+ * range operate with the AC97_MICBOOST bit enabled.  Computed values outside

+ * of this range are forced back into this range, but with the AC97_MICBOOST

+ * bit turned off.  This allows access to the very low dB range scale of the

+ * AC97 codec, which cannot be accessed with the MICBOOST bit enabled. -dln-

+ */

+

+#define MIC_NATURAL_SCALE    (32)

+

 /* table to scale scale from OSS mixer value to AC97 mixer register value */	

 static struct ac97_mixer_hw {

 	unsigned char offset;

@@ -251,7 +274,7 @@

 	[SOUND_MIXER_PCM]	=	{AC97_PCMOUT_VOL,	32},

 	[SOUND_MIXER_SPEAKER]	=	{AC97_PCBEEP_VOL,	16},

 	[SOUND_MIXER_LINE]	=	{AC97_LINEIN_VOL,	32},

-	[SOUND_MIXER_MIC]	=	{AC97_MIC_VOL,		32},

+	[SOUND_MIXER_MIC]	=	{AC97_MIC_VOL,		46},

 	[SOUND_MIXER_CD]	=	{AC97_CD_VOL,		32},

 	[SOUND_MIXER_ALTPCM]	=	{AC97_HEADPHONE_VOL,	64},

 	[SOUND_MIXER_IGAIN]	=	{AC97_RECORD_GAIN,	16},

@@ -302,7 +325,7 @@

    about that given mixer, and should be holding a spinlock for the card */

 static int ac97_read_mixer(struct ac97_codec *codec, int oss_channel) 

 {

-	u16 val;

+	u16 val, t;

 	int ret = 0;

 	int scale;

 	struct ac97_mixer_hw *mh = &ac97_hw[oss_channel];

@@ -340,7 +363,10 @@

 		scale = (1 << codec->bit_resolution);

 		ret = 100 - (((val & 0x1f) * 100) / scale);

 	} else if (oss_channel == SOUND_MIXER_MIC) {

-		ret = 100 - (((val & 0x1f) * 100) / mh->scale);

+		t = val & (MIC_NATURAL_SCALE - 1);

+		if (!(val & AC97_MICBOOST))

+			t += (mh->scale - MIC_NATURAL_SCALE);

+		ret = 100 - ((t * 100) / mh->scale-1);

 		/*  the low bit is optional in the tone sliders and masking

 		    it lets us avoid the 0xf 'bypass'.. */

 	} else if (oss_channel == SOUND_MIXER_BASS) {

@@ -427,7 +453,7 @@

 		left = ((100 - left) * mh->scale) / 100;

 		if (left >= mh->scale)

 			left = mh->scale-1;

-		val = left;

+	val = left;

 	} else if (oss_channel == SOUND_MIXER_PHONEOUT) {

 		scale = (1 << codec->bit_resolution);

 		left = ((100 - left) * scale) / 100;

@@ -436,13 +462,17 @@

 		val = left;

 	} else if (oss_channel == SOUND_MIXER_MIC) {

 		val = codec->codec_read(codec , mh->offset) & ~0x801f;

-		left = ((100 - left) * mh->scale) / 100;

+		left = ((100 - left) * mh->scale-1) / 100;

 		if (left >= mh->scale)

-			left = mh->scale-1;

+			left = mh->scale-1

+		if (left < MIC_NATURAL_SCALE)

+			left |= AC97_MICBOOST;

+		else

+			left -= (mh->scale - MIC_NATURAL_SCALE);

 		val |= left;

 		/*  the low bit is optional in the tone sliders and masking

 		    it lets us avoid the 0xf 'bypass'.. */

-	}

+	

 #ifdef DEBUG

 	printk(" 0x%04x", val);

 #endif