From bc4bbc4a92a8e9fb87aab1641f3868f7345b9b1e Mon Sep 17 00:00:00 2001
From: Martin Wilck <martin.wilck@ts.fujitsu.com>
Date: Tue, 21 Apr 2015 17:55:38 +0200
Subject: [PATCH] hda-codec: use smaller dynamic range for input amplifier

This patch addresses the following problem:

Moving the input volume slider 0% to 1% in a Win7 guest causes the
the "gain" values in the emulated HDA codec HW to jump from 0 to 40.
This makes it impossible to control sound volume in the low-gain
range using the windows guest.
This is related to how the Windows HDA codec driver and the QEMU
emulated HW interact. It seems that Windows uses a ~30dB overall
scale for the min-max range of the input volume slider.

The "right" solution for this problem would be to implement
proper dB scaling in QEMU and the audio backends (such as spice).

While this clean solution is not available, I suggest to decrease
the dynamic range for the the emulated Amps in the QEMU hda codec.
Experiments showed that with 32dB dynamic range with a 0.5 dB step,
it was possible to set gain values as low as 5 (-29.5dB / 8%).
Actual HW seems to use similar ranges for input amplifiers.

Signed-off-by: Martin Wilck <martin.wilck@ts.fujitsu.com>
---
 hw/audio/hda-codec-common.h | 23 +++++++++++++++--------
 hw/audio/hda-codec.c        | 23 +++++++++++++++++------
 2 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/hw/audio/hda-codec-common.h b/hw/audio/hda-codec-common.h
index b4fdb51..d59781b 100644
--- a/hw/audio/hda-codec-common.h
+++ b/hw/audio/hda-codec-common.h
@@ -28,16 +28,22 @@
 #define QEMU_HDA_ID_OUTPUT  ((QEMU_HDA_ID_VENDOR << 16) | 0x12)
 #define QEMU_HDA_ID_DUPLEX  ((QEMU_HDA_ID_VENDOR << 16) | 0x22)
 #define QEMU_HDA_ID_MICRO   ((QEMU_HDA_ID_VENDOR << 16) | 0x32)
-#define QEMU_HDA_AMP_CAPS                                               \
+#define QEMU_HDA_AMP_OUT_CAPS						\
     (AC_AMPCAP_MUTE |                                                   \
-     (QEMU_HDA_AMP_STEPS << AC_AMPCAP_OFFSET_SHIFT)    |                \
-     (QEMU_HDA_AMP_STEPS << AC_AMPCAP_NUM_STEPS_SHIFT) |                \
-     (3                  << AC_AMPCAP_STEP_SIZE_SHIFT))
+     (QEMU_HDA_AMP_OUT_STEPS << AC_AMPCAP_OFFSET_SHIFT)    |            \
+     (QEMU_HDA_AMP_OUT_STEPS << AC_AMPCAP_NUM_STEPS_SHIFT) |            \
+     (QEMU_HDA_AMP_OUT_STEP_SIZE << AC_AMPCAP_STEP_SIZE_SHIFT))
+#define QEMU_HDA_AMP_IN_CAPS						\
+    (AC_AMPCAP_MUTE |                                                   \
+     (QEMU_HDA_AMP_IN_STEPS << AC_AMPCAP_OFFSET_SHIFT)    |             \
+     (QEMU_HDA_AMP_IN_STEPS << AC_AMPCAP_NUM_STEPS_SHIFT) |             \
+     (QEMU_HDA_AMP_IN_STEP_SIZE << AC_AMPCAP_STEP_SIZE_SHIFT))
 #else
 #define QEMU_HDA_ID_OUTPUT  ((QEMU_HDA_ID_VENDOR << 16) | 0x11)
 #define QEMU_HDA_ID_DUPLEX  ((QEMU_HDA_ID_VENDOR << 16) | 0x21)
 #define QEMU_HDA_ID_MICRO   ((QEMU_HDA_ID_VENDOR << 16) | 0x31)
-#define QEMU_HDA_AMP_CAPS   QEMU_HDA_AMP_NONE
+#define QEMU_HDA_AMP_OUT_CAPS   QEMU_HDA_AMP_NONE
+#define QEMU_HDA_AMP_IN_CAPS   QEMU_HDA_AMP_NONE
 #endif
 
 
@@ -61,7 +67,7 @@ static const desc_param glue(common_params_audio_dac_, PARAM)[] = {
         .val = QEMU_HDA_AMP_NONE,
     },{
         .id  = AC_PAR_AMP_OUT_CAP,
-        .val = QEMU_HDA_AMP_CAPS,
+        .val = QEMU_HDA_AMP_OUT_CAPS,
     },
 };
 
@@ -86,7 +92,7 @@ static const desc_param glue(common_params_audio_adc_, PARAM)[] = {
         .val = AC_SUPFMT_PCM,
     },{
         .id  = AC_PAR_AMP_IN_CAP,
-        .val = QEMU_HDA_AMP_CAPS,
+        .val = QEMU_HDA_AMP_IN_CAPS,
     },{
         .id  = AC_PAR_AMP_OUT_CAP,
         .val = QEMU_HDA_AMP_NONE,
@@ -453,4 +459,5 @@ static const desc_codec glue(micro_, PARAM) = {
 #undef QEMU_HDA_ID_OUTPUT
 #undef QEMU_HDA_ID_DUPLEX
 #undef QEMU_HDA_ID_MICRO
-#undef QEMU_HDA_AMP_CAPS
+#undef QEMU_HDA_AMP_IN_CAPS
+#undef QEMU_HDA_AMP_OUT_CAPS
diff --git a/hw/audio/hda-codec.c b/hw/audio/hda-codec.c
index 3c03ff5..44c9a28 100644
--- a/hw/audio/hda-codec.c
+++ b/hw/audio/hda-codec.c
@@ -116,7 +116,17 @@ static void hda_codec_parse_fmt(uint32_t format, struct audsettings *as)
 #define QEMU_HDA_PCM_FORMATS (AC_SUPPCM_BITS_16 |       \
                               0x1fc /* 16 -> 96 kHz */)
 #define QEMU_HDA_AMP_NONE    (0)
-#define QEMU_HDA_AMP_STEPS   0x4a
+/* Amplifier properties */
+/* Step size: 0: 0.25dB 1: 0.5dB 2: 0.75dB 3: 1dB */
+/* 
+   Until we have a way to propagate dB values cleanly to the host
+   e.g. through spice, it is better to use a smaller dynamic range
+   for input. Here we use 0x40 * 0.5 dB = 32dB.
+*/
+#define QEMU_HDA_AMP_OUT_STEPS   0x4a
+#define QEMU_HDA_AMP_OUT_STEP_SIZE  3
+#define QEMU_HDA_AMP_IN_STEPS    0x4a
+#define QEMU_HDA_AMP_IN_STEP_SIZE   1
 
 #define   PARAM mixemu
 #define   HDA_MIXER
@@ -258,15 +268,16 @@ static void hda_audio_set_amp(HDAAudioStream *st)
     left  = st->mute_left  ? 0 : st->gain_left;
     right = st->mute_right ? 0 : st->gain_right;
 
-    left = left * 255 / QEMU_HDA_AMP_STEPS;
-    right = right * 255 / QEMU_HDA_AMP_STEPS;
-
     if (!st->state->mixer) {
         return;
     }
     if (st->output) {
+        left = left * 255 / QEMU_HDA_AMP_OUT_STEPS;
+        right = right * 255 / QEMU_HDA_AMP_OUT_STEPS;
         AUD_set_volume_out(st->voice.out, muted, left, right);
     } else {
+        left = left * 255 / QEMU_HDA_AMP_IN_STEPS;
+        right = right * 255 / QEMU_HDA_AMP_IN_STEPS;
         AUD_set_volume_in(st->voice.in, muted, left, right);
     }
 }
@@ -502,8 +513,8 @@ static int hda_audio_init(HDACodecDevice *hda, const struct desc_codec *desc)
             st->node = node;
             if (type == AC_WID_AUD_OUT) {
                 /* unmute output by default */
-                st->gain_left = QEMU_HDA_AMP_STEPS;
-                st->gain_right = QEMU_HDA_AMP_STEPS;
+                st->gain_left = QEMU_HDA_AMP_OUT_STEPS;
+                st->gain_right = QEMU_HDA_AMP_OUT_STEPS;
                 st->bpos = sizeof(st->buf);
                 st->output = true;
             } else {
-- 
2.1.0

