我尝试各种办法，wm8960始终不能得到声音输出。调试过程如下：
首先，打开电源使能脚：
ret=gpio_request(SABRESD_CODEC_PWR_EN,"audio_pwr_en");
if (!ret){
printk("Turn on audio(wm8962)power!(1:enable) ");
gpio_direction_output(SABRESD_CODEC_PWR_EN,1); // 0:enable, 1:disable
gpio_free(SABRESD_CODEC_PWR_EN);
}
串口打印如下出错信息：
wm8962 0-001a: Failed to get supply 'SPKVDD1':-19
wm8962 0-001a: Failed to request supplies: -19
wm8962 0-001a: asoc: failed to probe CODECwm8962.0-001a: -19
asoc: failed toinstantiate card wm8962-audio: -19
InitializeHDMI-audio failed. Load HDMI-video first!
ALSA device list:
No soundcards found.
把imx6q_init_audio();后移几行，上面的错误就没有了。但出现下面错误 ：
wm8962 0-001a: Device is not a WM8962, ID 0 !=6243
wm8962 0-001a: asoc: failed to probe CODECwm8962.0-001a: -22
asoc: failed toinstantiate card wm8962-audio: -22
把sound/soc/codec/下面的wm8962.c改用wm8960.c（修改Kconfig和Makefile）。
wm8960_i2c_probe不调用。原因是：
.driver = {
.name = "wm8960",
而 {
I2C_BOARD_INFO("wm8962", 0x1a),
.platform_data =&wm8962_config_data,
},
linux driver是根据name来匹配的，如果匹配就调用。
登记了snd_soc_register_codec后，codec的probe也不调用。
原因是下面这个snd_dai_driver的name要一致才能调用。
static struct snd_soc_dai_driver wm8960_dai = {
.name = "wm8960",
static structsnd_soc_dai_link imx_dai[] = {
{
.name = "HiFi",
.stream_name = "HiFi",
.codec_dai_name = "wm8960",
调用后显示：
wm8960 0-001a: wm8960 probed success!
wm8960 0-001a: Failed to add routeHPOUTL->Headphone Jack
asoc: wm8960<-> imx-ssi.1 mapping ok
input:wm8960-audio DMIC as /devices/platform/soc-audio.5/sound/card0/input1
input:wm8960-audio Ext Spk as /devices/platform/soc-audio.5/sound/card0/input2
ALSA device list:
#0: wm8960-audio
root@imx6solo ~$find / -name *wm8960*
/sys/devices/platform/imx-wm8960.0
/sys/bus/platform/devices/imx-wm8960.0
/sys/bus/platform/drivers/imx-wm8960
/sys/bus/platform/drivers/imx-wm8960/imx-wm8960.0
/sys/bus/i2c/drivers/wm8960
/proc/asound/wm8960audio
root@imx6solo ~$
问题是/dev/下面并没有增加设备，无法使用/dev/pcm。
root@imx6solo/usr/bin$ aplay -L
null
Discard all samples (playback) or generatezero samples (capture)
root@imx6solo/usr/bin$ aplay -l
**** List ofPLAYBACK Hardware Devices ****
card 0:wm8960audio [wm8960-audio], device 0: HiFi wm8960-0 []
Subdevices: 1/1
Subdevice #0: subdevice #0
root@imx6solo/usr/bin$
现在应该是试试ALSA驱动程序是不是真能用的时候了. 接者就是使用它.
查看声卡是否存在：
root@imx6solo ~$cat /proc/asound/cards
0 [wm8960audio ]: wm8960-audio - wm8960-audio
wm8960-audio
ALSA 驱动程序在 /dev/snd/ 目录下有自己的驱动程序。
root@imx6solo ~$ ls /dev/snd/
controlC0 pcmC0D0c pcmC0D0p timer
http://www.alsa-project.org/main/index.php/Download上面下载alsa tester包括alsa-lib,alsa-utils。
编译：./gitcompile CC=arm-linux-gcc --host=arm-linux
现在进化到configure都从网络上临时下载的地步了，我有点out了。
编译alsa-utils总是过不去。重新下载alsaplayer。
./configure--host=arm-linux CC=arm-linux-gcc --disable-oggvorbis
然后make.
对比了wm8960.c/wm8962.c,imx-wm8960.c/imx-wm8962.c，差别其实非常大。
http://bbs.21ic.com/forum.php?mod=viewthread&tid=869393，从这个链接地址可以下载imx-wm8960.c。
重新配置linux kernel，设备/dev/dsp和/dev/mixer出来，这是OSS接口的要求。
root@imx6solo/test/audio$ ./wavplay test.wav
-------------------------------------------------------------------->
File Magic: [RIFF]
File Length: [424636]
File Type: [WAVE]
Fmt Magic: [fmt ]
Fmt Size: [16]
Fmt Format: [PCM]
Fmt Channels: [2]
FmtSample_rate: [22050](HZ)，22khz
FmtBytes_p_second: [88200]
FmtBlocks_align: [4]
FmtSample_length: [16]
Chunk Type: [data]
Chunk Length: [424600]
<--------------------------------------------------------------------
Plug PCM: Rateconversion PCM (44100, sformat=S16_LE)
Converter:linear-interpolation
Protocol version:10002
Its setup is:
stream : PLAYBACK
access : RW_INTERLEAVED
format : S16_LE
subformat : STD
channels : 2
rate : 22050
exact rate : 22050 (22050/1)
msbits : 16
buffer_size : 8192
period_size : 256
period_time : 11609
tstamp_mode : NONE
period_step : 1
avail_min : 256
period_event : 0
start_threshold : 1
stop_threshold : 8192
silence_threshold: 0
silence_size : 0
boundary : 536870912
Slave: DirectStream Mixing PCM
Its setup is:
stream : PLAYBACK
access : MMAP_INTERLEAVED
format : S16_LE
subformat : STD
channels : 2
rate : 44100 //44khz
exact rate : 44100 (44100/1)
msbits : 16
buffer_size : 16384
period_size : 512
period_time : 11609
tstamp_mode : NONE
period_step : 1
avail_min : 512
period_event : 0
start_threshold : 2
stop_threshold : 16384
silence_threshold: 0
silence_size : 0
boundary : 1073741824
Hardware PCM card0 'wm8960-audio' device 0 subdevice 0
Its setup is:
stream : PLAYBACK
access : MMAP_INTERLEAVED
format : S16_LE
subformat : STD
channels : 2
rate : 44100 //44khz
exact rate : 44100 (44100/1)
msbits : 16
buffer_size : 16384
period_size : 512
period_time : 11609
tstamp_mode : ENABLE
period_step : 1
avail_min : 512
period_event : 0
start_threshold : 1
stop_threshold : 1073741824
silence_threshold: 0
silence_size : 1073741824
boundary : 1073741824
appl_ptr : 0
hw_ptr : 0
root@imx6solo/test/audio$ aplay test.wav
Playing WAVE'test.wav' : Signed 16 bit Little Endian, Rate 22050 Hz, Stereo
Aborted by signalInterrupt...
root@imx6solo/test/audio$
仍然是没有声音输出！！
换了一个44khz采集率的wav文件，仍然没有声音输出！
root@imx6solo/test/audio$ aplay xihuanni.wav
Playing WAVE'xihuanni.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo
Aborted by signalInterrupt...
再次检查了pin mux config，是正确的。但就是没有任何audio输出！
如果直接用imx-wm8962.c，则有许多出错信息，如下：
root@imx6solo/test/audio$ aplay xihuanni.wav
WM8960 PLL:Unsupported N=3
Failed to startFLL: -22
Failed to setSYSCLK: -22
asoc: machinehw_params failed
Failed to setSYSCLK: -22
ALSA libpcm_direct.c:980:(snd1_pFailed to set SYSCLK: -22
cm_direct_initialize_slave)unable to install hw params
ALSA libpcm_dmix.c:1030:(snd_pcm_dmix_open) unable to initialize slave
aplay: main:660:audio open error: Invalid argument
所以，要用imx-wm8962.c来修改的话，还有点麻烦，不会很容易。
网上找了一个人交流，他用的是imx-wm8960.module，就是编译出来的.o
ifneq ($(wildcardsound/soc/imx/imx-wm8960.c),)
snd-soc-imx-wm8960-objs:= imx-wm8960.c
else
snd-soc-imx-wm8960-objs:= imx-wm8960.module
endif
我这样修改后，运行导致crash。
register wm8960 I2C driver success!
Unable to handlekernel paging request at virtual address f8f2fe18
pgd = 80004000
[f8f2fe18] *pgd=1bce9811, *pte=00000000,*ppte=00000000
Internal error:Oops: 807 [#1] PREEMPT
Modules linked in:
CPU: 0 Not tainted (3.0.101-2790-gc248ed7 #274)
先验证了i2c，示波器显示有输出，并且测了看device addr也是0x1A。
alsamixer配置也是全部拉高，退出后重新进入，也是对的，可以保存和读出。
i2s data仍然没有，数据线对地电阻也测了，并没有短路。
仔细查了linux代码，没有i2s部分，应该是改成SSI了。
ssi有两个，一个是在driver/mxc/ssi.c，这个是以前的。
现在是sound/soc/imx/imx-ssi.c。
imx6q_add_imx_ssi(1,&mx6_sabresd_ssi_pdata); 注册为platform device。
加了一句打印：
imx_ssi_probesuccessfully。证明probe是被调用了的。
root@imx6solo/test/audio$ aplay xihuanni.wav
snd_pcm_dmix_open()
snd1_pcm_hw_open_fd()
snd_pcm_plug_open()
Playing WAVE'xihuanni.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
snd_pcm_mmap_writei
然后挂起，ssi接口无输出，应该是mixer配置不正确。
最终查明原因，是没有正确初始化wm8960导致的。
在imx-wm8960.c的
static int imx_hifi_hw_params(struct snd_pcm_substream *substream,
struct snd_pcm_hw_params *params)函数中增加：
...
wm8960_vendor_set(codec_dai);
...
/* based on the result of dump */
void wm8960_vendor_set(struct snd_soc_dai *codec_dai)
{
struct snd_soc_codec *codec = codec_dai->codec;
snd_soc_write(codec, 0x19, 0xc0); /* power1, ok*/
snd_soc_write(codec, 0x1a, 0x199); /* power2, ok*/
snd_soc_write(codec, 0x31, 0xf7); /* classd1 : enable L&R, ok */
snd_soc_write(codec, 0x33, 0x11b); /* classd3 : volume max, ok */
snd_soc_write(codec, 0x28, 0x179); /* ok */
snd_soc_write(codec, 0x29, 0x179); /* ok */
snd_soc_write(codec, 0x22, 0x100); /* dac to mixer, ok */
snd_soc_write(codec, 0x25, 0x100); /* dac to mixer, ok */
snd_soc_write(codec, 0x2f, 0x0c); /* left & right output mixer enable, ok */
snd_soc_write(codec, 0x05, 0x00); /* ok */
}