topic Re: SGTL5000 CODEC line-in noise on i.MX28 in i.MX Processors

SGTL5000 CODEC line-in noise on i.MX28

CraigMcQueen — Wed, 22 May 2013 05:21:26 GMT

We are developing a system based on i.MX28, which does audio input and output through the SGTL5000 CODEC.

Our software works fine most of the time, however, sometimes after boot-up (maybe 10-20% of the time) the audio input via SGTL5000 ADC_IN is very noisy. It persists even if I stop and restart audio input. (Normally the software is doing two-way audio streaming, but I also get the same sort of noise via 'arecord test.wav'.) If I power cycle the unit, then usually audio is fine after the power cycle.

We're using the Linux 2.6.35 kernel. The problem occurred both before and after applying the Freescale patches "patches_for_L2.6.35_MX28_SDK_10.12_SOURCE.tar.gz".

The noise sounds as though it's due to a gain setting that is sometimes starting up in an indeterminate state, with a higher gain setting than "normal". Sometimes it sounds like bad clipping of the input, when gain is set too high. Sometimes it sounds like plain noise, regardless of the input.

I tried compiling the kernel audio drivers as a module, and loading/unloading via "modprobe" command. When the problem occurs, it persists even if I do "modprobe -r" then "modprobe" to reload the audio driver.

It looks as though it might be some sort of issue with the SGTL5000 CODEC coming up in an indeterminate state for some register settings, and the Linux SGTL5000 driver doesn't fix it.

Has anyone else seen this issue?

Is there an easy way I can see a dump of all SGTL5000 register settings with/without this noise issue present, to test my hypothesis?

Re: SGTL5000 CODEC line-in noise on i.MX28

fabio_estevam — Thu, 23 May 2013 00:48:14 GMT

Can you test a 3.9 kernel and let us know if the issue is also there?

Re: SGTL5000 CODEC line-in noise on i.MX28

CraigMcQueen — Thu, 23 May 2013 02:03:06 GMT

Fabio Estevam wrote:

Can you test a 3.9 kernel and let us know if the issue is also there?

Hmm, maybe. We're using Timesys for builds, and Timesys is currently supporting 2.6.35 without the latest Freescale patches (I added the Freescale patches myself).

But if there's a 3.9 kernel repository that supports the i.MX28 EVK, I could perhaps try that.

Re: SGTL5000 CODEC line-in noise on i.MX28

PeterChan — Thu, 23 May 2013 04:03:16 GMT

Hello Craig,

Could you please try this patch? It reset the SAIF1 to get rid of the recording noise.

Re: SGTL5000 CODEC line-in noise on i.MX28

CraigMcQueen — Thu, 23 May 2013 07:14:49 GMT

Thanks very much for providing this patch. This is a big help. Initial results indicate this patch did seem to help, but not fix it entirely.

I have done about 10 power cycles. On none of those did I get noisy input. However, twice when I've closed and re-opened the audio device, I've got noisy input. Then on those two occasions, when I've closed and re-opened the audio device again, the noise disappeared.

This is an improvement on previous behaviour, where the noise persisted even if I closed and re-opened the audio device.

So is this a SAIF driver issue, rather than a SGTL5000 driver issue? And why do you think I would still be getting noise sometimes?

Re: SGTL5000 CODEC line-in noise on i.MX28

PeterChan — Thu, 23 May 2013 10:40:27 GMT

Could you please tell me how did you close and re-open the audio device so that I can reproduce the noise issue?

The system clock of SGTL5000 comes from the SAIF0_MCLK. If SAIF0 is reset, theSAIF0_MCLK is interrupted and you may need to re-initialize the SGTL5000 again.

Re: SGTL5000 CODEC line-in noise on i.MX28

CraigMcQueen — Thu, 23 May 2013 23:22:44 GMT

PeterChan wrote:

Could you please tell me how did you close and re-open the audio device so that I can reproduce the noise issue?

I am using a C program that does bi-directional audio streaming using libmediastreamer. It's doing 8 kHz audio in both directions.

PeterChan wrote:

The system clock of SGTL5000 comes from the SAIF0_MCLK. If SAIF0 is reset, theSAIF0_MCLK is interrupted and you may need to re-initialize the SGTL5000 again.

I hope this sort of detail is all taken care of by the Linux SGTL5000 audio driver.

Re: SGTL5000 CODEC line-in noise on i.MX28

PeterChan — Fri, 24 May 2013 10:11:31 GMT

Yes, the linux SGTL5000 and SAIF audio driver should take care of all the detail about the link.

I tested the audio stream open/close by running this command repeatedly but not yet able to hear noise.

"arecord -t wav -c 2 -r 44100 -f S16_LE -d 3 | aplay"

You may need to hack into linux/sound/soc/mxs/mxs-dai.c to find out if SAIF0 has been reset in between close and re-open the audio device.

Re: SGTL5000 CODEC line-in noise on i.MX28

CraigMcQueen — Fri, 31 May 2013 00:51:16 GMT

I have been testing this further. The noise cases are uncommon, and I have been unable to isolate the problem so far.

I also tested open/close using ecasignalview from ecasound, to loop-back audio input to output and also show the signal level:

ecasignalview -b:256 -f:,,8000 alsahw alsahw

By that method, I was also unable to reproduce the noise issue in multiple tests.

I also ran my code (that uses libmediastreamer) in isolation, and could not reproduce the noise issue in multiple tests.

Now I have two possible theories about interaction with other elements of the system:

1) It is also displaying information on a display on the I2C bus. Could I2C bus activity disturb normal SGTL5000 CODEC initialisation?

2) It is communicating through a radio module. Maybe power load on the system when the radio module begins communications (at about the same time the audio devices are opened) is glitching the power rails.

(2) doesn't seem likely. But (1) may be an issue. We've had issues with audio previously, when the I2C bus was (I think) trying to talk to an I2C device that wasn't communicating. See: Re: sgtl5000 problem on i.mx28. Could these be related?

Re: SGTL5000 CODEC line-in noise on i.MX28

CraigMcQueen — Fri, 31 May 2013 03:19:38 GMT

Now I have two possible theories about interaction with other elements of the system:

1) It is also displaying information on a display on the I2C bus. Could I2C bus activity disturb normal SGTL5000 CODEC initialisation?

2) It is communicating through a radio module. Maybe power load on the system when the radio module begins communications (at about the same time the audio devices are opened) is glitching the power rails.

(2) doesn't seem likely. But (1) may be an issue. We've had issues with audio previously, when the I2C bus was (I think) trying to talk to an I2C device that wasn't communicating. See: Re: sgtl5000 problem on i.mx28. Could these be related?

I tested (1), by doing audio tests while a test program was writing lots of data on the I2C bus. I did 30 audio tests, and had no noise issues. So I think this rules out the I2C bus hypothesis.

Since applying the patch supplied by Peter Chan, I've only had the 2 instances of noise, and never since then. I've probably done 80 or so tests, without noise.

Re: SGTL5000 CODEC line-in noise on i.MX28

ThomasBandelier — Mon, 07 Oct 2013 09:02:56 GMT

Hi Craig, Peter,

We are running into same issue as you had. The provided patch also helped, but we still get the noise around 1 on 60 iterations.

Has any other patch been implemented for this ? I can not see any other activity related to this.

Peter, we are in discussion we technical support Jack Lee about this.

Waiting for your feedback,

Thomas

Re: SGTL5000 CODEC line-in noise on i.MX28

PeterChan — Thu, 10 Oct 2013 01:06:38 GMT

Hi Thomas,

We are sorry for the audio noise issue. Jack and I are sharing the same information and we are now working on this.

Regards,

Peter

Re: SGTL5000 CODEC line-in noise on i.MX28

fabio_estevam — Thu, 10 Oct 2013 04:01:55 GMT

Thomas,

Could you please tell me how I can reproduce this issue? Is it possible to reproduce it via standard alsa utilities, such as aplay/arecord?

Could you try kernel 3.12-rc4?

Regards,

Fabio Estevam

Re: SGTL5000 CODEC line-in noise on i.MX28

aidamynzhasova — Wed, 30 Oct 2013 13:13:25 GMT

Hi Fabio,

I observe audio noise issue on mainline kernel, which is based on linux-next repository, master branch (last commit: 3a94271d0798fe2a2e5bfe2d135f2c8f6db2e80b).

I didn't make any changes, just built mxs-defconfig-based uImage and imx28-evk.dtb and loaded on my i.MX28 EVK REV D board.

After that I tried to record something:

~ # arecord -D hw:0,1 -t wav -c 2 -r 44100 -f S16_LE -d 5 awesome.wav

Recording WAVE 'awesome.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo

...and play it:

~ # aplay -D plughw:0,0 awesome.wav

Playing WAVE 'awesome.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo

I heard only random noise.

Here is the list of devices:

~ # aplay -l

**** List of PLAYBACK Hardware Devices ****

card 0: mxssgtl5000 [mxs_sgtl5000], device 0: HiFi Playback sgtl5000-0 []

Subdevices: 1/1

Subdevice #0: subdevice #0

~ # arecord -l

**** List of CAPTURE Hardware Devices ****

card 0: mxssgtl5000 [mxs_sgtl5000], device 1: HiFi Capture sgtl5000-1 []

Subdevices: 1/1

Subdevice #0: subdevice #0

Please, help!

Re: SGTL5000 CODEC line-in noise on i.MX28

fabio_estevam — Wed, 30 Oct 2013 15:12:04 GMT

Hi Aida,

From your description, it looks like the LINE_IN option is not selected in alsamixer.

Please run alsamixer and make sure that LINE_IN is selected for the capture.

Regards,

Fabio Estevam

Re: SGTL5000 CODEC line-in noise on i.MX28

aidamynzhasova — Wed, 30 Oct 2013 15:33:15 GMT

Fabio,

thanks for reply. I've tried to change "Capture Mux" to LINE_IN, but in this case I don't hear even noise, just silence.

Re: SGTL5000 CODEC line-in noise on i.MX28

fabio_estevam — Wed, 30 Oct 2013 16:53:38 GMT

Aida,

When selecting LINE_IN, please make sure you are connecting a stereo audio source to the LINE_IN jack.

I usually connect my notebook analog output to the mx28evk LINE_IN jack.

Double check the volume level you are applying as well.

I don't have my mx28evk at the moment to try, but linux-next with arecord/aplay a few weeks ago and it was working.

Regards,

Fabio Estevam

Re: SGTL5000 CODEC line-in noise on i.MX28

aidamynzhasova — Thu, 31 Oct 2013 10:21:37 GMT

Fabio,

I tried line input and it works. Thanks very much for your help!

Re: SGTL5000 CODEC line-in noise on i.MX28

fabio_estevam — Tue, 26 Nov 2013 15:43:16 GMT

Hi Craig,

Please apply the four patches from Jack Lee available at:

http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/log/?h=imx_2.6.35_maintain

Regards,

Fabio Estevam

Re: SGTL5000 CODEC line-in noise on i.MX28

CraigMcQueen — Sun, 09 Feb 2014 23:01:50 GMT

I've recently been trying the imx_2.6.35_maintain branch of Freescale's repository. I'm finding problems with Jack Lee's patches—maybe they fix the noise issue, however they also introduce other problems: it's not possible to playback and record at different sample rates. E.g. using aplay and arecord:

In one terminal:

# aplay testing_1_2_3_4_repeated.wav

Playing WAVE 'testing_1_2_3_4_repeated.wav' : Signed 16 bit Little Endian, Rate 8000 Hz, Mono

while in another terminal:

# arecord -r 16000 /tmp/test.wav

Recording WAVE '/tmp/test.wav' : Unsigned 8 bit, Rate 16000 Hz, Mono

The arecord doesn't show any error messages, however it doesn't get any audio data. The file /tmp/test.wav is just 44 bytes.

I'm using a somewhat modified sound driver, due to the hardware we're using which is based on SGTL5000 but with some changes. I modified my code to match up with these patches, namely, duplicating a change in the ALSA SoC machine driver of sound/soc/mxs/mxs-devb.c — and I'm still having this issue.

If I record at the same sample rate as the play, then it is okay.