linux-kernel - Re: [PATCHv2 1/4] ASoC: simple-card: add asoc_simple_card_fmt

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Date:	Wed, 3 Sep 2014 11:36:39 +0300
From:	Jyri Sarha <jsarha@...com>
To:	"Li.Xiubo@...escale.com" <Li.Xiubo@...escale.com>,
	"broonie@...nel.org" <broonie@...nel.org>,
	"perex@...ex.cz" <perex@...ex.cz>,
	"lgirdwood@...il.com" <lgirdwood@...il.com>,
	"tiwai@...e.de" <tiwai@...e.de>,
	"moinejf@...e.fr" <moinejf@...e.fr>,
	"andrew@...n.ch" <andrew@...n.ch>,
	"kuninori.morimoto.gx@...esas.com" <kuninori.morimoto.gx@...esas.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"pawel.moll@....com" <pawel.moll@....com>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"galak@...eaurora.org" <galak@...eaurora.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2 1/4] ASoC: simple-card: add asoc_simple_card_fmt_master()
 to simplify the code.

On 09/03/2014 05:37 AM, Li.Xiubo@...escale.com wrote:
>> Subject: Re: [PATCHv2 1/4] ASoC: simple-card: add asoc_simple_card_fmt_master()
...
>>
>> This won't work. The logic for cpu node needs to be negated for codec node.
>>
>
> Yes, actually it should be.
>
> As my previous patches about this:
> ----
> Since from the DAI format micro SND_SOC_DAIFMT_CBx_CFx, the 'CBx'
> mean Codec's bit clock is as master/slave and the 'CFx' mean Codec's
> frame clock is as master/slave.
>
> So these same DAI formats should be informed to CPU and CODE DAIs at
> the same time. For the Codec driver will set the bit clock and frame
> clock as the DAI formats said, but for the CPU driver, if the the
> bit clock or frame clock is as Codec master, so it should be set CPU
> DAI device as bit clock or frame clock as slave, and vice versa.
>
> The old code will cause confusion, and we should be clear that the
> letter 'C' here mean to Codec.
> ----
>
> For the master format, no matter for CPU or CODEC, it always means Codec
> is master or slave for bit/frame clock, not means the local DAI device's
> bit/frame clock as master or slave.
>
> So your CPU DAI device driver should negate this locally as the existed
> Ones do.
>


Yes, but there is double negation in this patch. The switch-case
assignments depend on whether the bitclkmaster and framemaster
DT-node pointers are compared to a cpu-dai-node or
codec-dai-node. When your patch compares the codec-node, it does
the decisions like it was a cpu-node, which produces inverted CBM
and CFM setting.

However, Kurinori-san's patch fixes this problem because it just
uses the daifmt generated by comparing to codec node for both cpu
and codec nodes.

The reason why I did the comparison per node basis, was to make
the code more ready for tdm setups with multiple codecs on a same
wire. But writing code for something that is not really needed
yet is usually a bad idea, like it was this time too.

Kurinori-san's version of the fix should be fine and it cleans up
the code quite nicely.

Best regards,
Jyri

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