linux-kernel - Re: [PATCH 04/11] MFD: twl4030-audio: Add DT support

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Date:	Thu, 09 Aug 2012 16:53:26 +0300
From:	Peter Ujfalusi <peter.ujfalusi@...com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
CC:	Samuel Ortiz <sameo@...ux.intel.com>, Liam Girdwood <lrg@...com>,
	Tony Lindgren <tony@...mide.com>,
	Dmitry Torokhov <dtor@...l.ru>, alsa-devel@...a-project.org,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org,
	Benoit Cousson <b-cousson@...com>
Subject: Re: [PATCH 04/11] MFD: twl4030-audio: Add DT support

On 08/09/2012 01:36 PM, Mark Brown wrote:
> On Thu, Aug 09, 2012 at 01:18:50PM +0300, Peter Ujfalusi wrote:
>> On 08/08/2012 05:49 PM, Mark Brown wrote:
> 
>>> That makes sense if the GPIO is actively driven, open drain should be
>>> better here, but it's still a generic thing which it'd be nice to
>>> extract.
> 
>> To cover all of this in a generic way is not that straight forward IMHO.
> 
> The sequence is just:
> 
>   1. Enable mutes (at _PRE time)
>   2. Do whatever the device needs
>   3. Disable the mutes (at _POST time)
> 
> I'm not sure there's any reason for you not to use the internal mute
> even if the external mute is present but if there is that's the only
> thing that's weird here.  If there's no reason not to do it it just goes
> into step 2 and then it's fine, even if there is you can make it
> conditional in step 2.

Not sure, but it should not cause issues. The PIN is multiplexed between
GPIO6/PWM0/MUTE functionality.
For that matter probably I could just don't care about flags here and
configure the extmute (the internal one) all the time. Not sure, it has been a
long time I have dealt with the twl4030...

>> Sure I could do this:
>> hs_extmute: if only this is set we shall use the chip built in functionality
>> hs_extmute_gpio: if this is set we use the extmute feature but with external
>>                  GPIO.
> 
>> But both need to be documented and supported.
> 
> Is there any actual case where an external mute is supplied via a
> mechanism other than a GPIO, and if there is would it not either need
> its own DT property or already need to interact with the driver from
> code, making the DT property redundant?

Not with my knowledge. The only board using it is the zoom2 upstream. I know
other boards (not in upstream) which either uses the internal mute or GPIO.

> My thinking here is that the
> flag should be redundant because we already need to specify how we do
> the mute, what I'd expect is that we activate the external mute
> functionality as a result of being given another way of doing it so we
> don't need to provide a flag.

I perfectly understand your point. However how would you imagine this in the core?
We should have something similar to DAPM_SUPPLY which we can attach to the
widget which needs this sort of mute, but how big change we would need in the
core to do this I'm not sure.
I can take a look at this, but I would do it as a follow up series.

-- 
Péter
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