linux-kernel - Re: [PATCH v9 1/4] drm/i2c: tda998x: Add DT support for audio

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Message-ID: <54AD6A5C.60903@arm.com>
Date:	Wed, 07 Jan 2015 17:18:20 +0000
From:	Andrew Jackson <Andrew.Jackson@....com>
To:	Jean-Francois Moine <moinejf@...e.fr>
CC:	Mark Brown <broonie@...nel.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Dave Airlie <airlied@...il.com>, Jyri Sarha <jsarha@...com>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 1/4] drm/i2c: tda998x: Add DT support for audio

On 01/07/15 17:08, Jean-Francois Moine wrote:
> On Wed, 07 Jan 2015 14:39:13 +0000
> Andrew Jackson <Andrew.Jackson@....com> wrote:
> 
>>> +  - audio-ports: must contain one or two values selecting the source
>>> +	in the audio port.
>>> +	The source type is given by the corresponding entry in
>>> +	the audio-port-names property.  
>>
>> I think that this entry might benefit from a little more explanation.
>> The value specified here selects which pins on the chip provide the
>> audio input doesn't it?  In the outline datasheet that I have these are
>> listed in table 17:
>>
>> Audio port 	Input configuration
>> 		S/PDIF 		I2S-bus
>> AP0 		- 		WS (word select)
>> AP1 		S/PDIF input 	I2S-bus channel 0
>> AP2 		S/PDIF input 	I2S-bus channel 1
>> AP3[1] 				I2S-bus channel 2
>> AP4[1] 				I2S-bus channel 3
>> ACLK 		- 		SCK (I2S-bus clock)
>>
>> [1] Depending on package.
> 
> Your table is close to the one in the TDA9983B documentation I have,
> but the pins are not exactly the same:
> 
> AP0 		WS (word select)
> AP1 		I2S-bus port 0
> AP2 		I2S-bus port 1
> AP3 		I2S-bus port 2
> AP4 		I2S-bus port 3
> AP5		MCLK (master clock for S/PDIF)
> AP6		S/PDIF input
> AP7		AUX (internal test)
> ACLK 		SCK (I2S-bus clock)
> 
> That's why I did not know clearly why I had to set AP2 for S/PDIF input
> and (AP0 + AP1) for I2S input in the Cubox.
> 
> Then, the only more explanation I could give is "have a look at the
> audio input format and at the register 0x1e page 0 in the documentation
> of the TDA998x chip".
> 
> BTW, the tda998x driver supports only the TDA9989, TDA19988 and
> TDA19989 chips. If the TDA9983B would be supported, the audio port
> definitions would be of no use.
> 
> So, what would you see as an explanation?
> 

I understand your difficulty!  I was just wanting something to clarify the 
meaning of the value without reference to the driver source.

You could add something like this to your existing explanation: "The value
describes which audio input pins are selected; this varies depending
on chip type so consult the section on audio port configuration in the 
relevant datasheet.".  

	Andrew

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