[ALSA] snd-emu10k1: Attenuate output volume to reduce distortion

Modules: EMU10K1/EMU10K2 driver

                      on Audigy 2 ZS Notebook.

Set the master volume to about 6 or 8% in alsamixer. This will
attenuate the output enough for better sound quality.
Note: Only stereo enabled at present.
The distortion is caused by the output path after the DSP
adding 12dB gain to the output while still in digital mode,
resulting in wrap around distortion.
Signed-off-by: James Courtier-Dutton <James@superbug.co.uk>

sound/pci/emu10k1/emu10k1_main.c

@@ -40,6 +40,7 @@
 #include <sound/core.h>
 #include <sound/emu10k1.h>
 #include "p16v.h"
+#include "tina2.h"
 
 #if 0
 MODULE_AUTHOR("Jaroslav Kysela <perex@suse.cz>, Creative Labs, Inc.");
@@ -600,6 +601,7 @@ static int __devinit snd_emu10k1_cardbus_init(emu10k1_t * emu)
 	outl(0x0090007f, special_port);
 	value = inl(special_port);
 
+	snd_emu10k1_ptr20_write(emu, TINA2_VOLUME, 0, 0xfefefefe); /* Defaults to 0x30303030 */
 	return 0;
 }
 

sound/pci/emu10k1/tina2.h

+/*
+ *  Copyright (c) by James Courtier-Dutton <James@superbug.demon.co.uk>
+ *  Driver p16v chips
+ *  Version: 0.21
+ *
+ *
+ *  This code was initally based on code from ALSA's emu10k1x.c which is:
+ *  Copyright (c) by Francisco Moraes <fmoraes@nc.rr.com>
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ *
+ */
+
+/********************************************************************************************************/
+/* Audigy2 Tina2 (notebook) pointer-offset register set, accessed through the PTR2 and DATA2 registers  */
+/********************************************************************************************************/
+
+#define TINA2_VOLUME	0x71	/* Attenuate playback volume to prevent distortion. */
+				/* The windows driver does not use this register,
+				 * so it must use some other attenuation method.
+				 * Without this, the output is 12dB too loud,
+				 * resulting in distortion.
+				 */
+