Re: WM8993: amp control, amplifying pops.

Re: WM8993: amp control, amplifying pops.

[Mark Brown]

On Mon, May 10, 2010 at 10:10:53AM +0800, Zhang JieJing wrote:

> I have a question about WM8993 codec's amplifying pops control.

Could you please be more specific about what you mean when you say
"amplifying pops control"?  What exactly is an "amplifying pop" (do you
mean that you hear an unwanted noise, or is there something else)?

Please ensure that you are using the latest version of the WM8993 driver
(including wm_hubs.c) to make sure that you have all the latest bug
fixes and enhancements.  If you are not using single ended line outputs
from the device you should also mark the line outputs as being in
differential mode for maximum power savings.

> Our board using a WM8993 codec, and I We have problem about ampifying pops,
> when the system resume, We will heard a ampifying pop, (but it's silence on
> the suspend processing), We also noticed that when system boot, also can
> hear one ampifying pop.

System resume and power up are identical from the point of view of the
CODEC driver.

> From I know, the WM8993's codec have a internal amplifier, I don't know how
> to control this amplifier.

The WM8993 has a large number of amplifiers, there are many audio paths
in the device and most of them have some amplification control.  Which
outputs are you concerned about?

Re: WM8993: amp control, amplifying pops.

[Mark Brown]

On Tue, May 11, 2010 at 11:07:38AM +0800, Zhang JieJing wrote:
> 2010/5/10 Mark Brown <broonie@opensource.wolfsonmicro.com>

> Hi, Our kernel version is 2.6.28, but port the wm8993 driver to this
> version's kernel.

Normally in these situations I would recommend backporting the entire
ASoC subsystem - it's fairly well isolated from the rest of the kernel
so this tends to be reasonably straightforward.

> the amplifying pop is when system resume, the speaker will hear one
> short pop noise,
> also, this short pop noise will hear the first time driver is opened.

When exactly do you hear this noise?  The WM8993 driver will not power
up the speaker outputs unless they are in use and there are no audio
paths configured to the speakers by default.  Are you configuring an
audio path in the CODEC at system startup?  Which mode do you have the
WM8993 speaker drivers in - class D or class A/B?

It might be helpful to capture all the register writes done when
bringing up the WM8993.  Also, if you are configuring an audio path from
an analogue input you should check that there is no DC offset present in
the input signal - if there is one then the WM8993 will reproduce it
into the output path, which would result in an audible noise.

> In 53242c68333570631a15a69842851b458eca3d99,
> there was a line:
> 
> +		ret = wm8993_set_fll(codec->dai, 0, wm8993->fll_src,
> +				     fll_fref, fll_fout);
> +

> but in lastest version of wm8993 driver, wm8993_set_fll will do
> nothing we the second parameter(fll_id) is 0,  so, I don't know what
> this function want to do,
> Cound you give me some idea ?

This parameter specifies which of the FLLs/PLLs in the device to
configure.  Since the WM8993 has only one FLL it just ignores this
parameter, other devices with multiple FLLs such as the WM8994 need this
to select between the FLLs.