linux-kernel - RE: [alsa-devel] [PATCH] ALSA: ASoC: McASP: Fix data rotation for playback. Enables 24bit audio playback

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Date:	Fri, 18 Jan 2013 08:48:36 +0000
From:	"Hebbar, Gururaja" <gururaja.hebbar@...com>
To:	Michal Bachraty <michal.bachraty@...eamunlimited.com>
CC:	"tiwai@...e.de" <tiwai@...e.de>, "perex@...ex.cz" <perex@...ex.cz>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"broonie@...nsource.wolfsonmicro.com" 
	<broonie@...nsource.wolfsonmicro.com>,
	"Girdwood, Liam" <lrg@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [alsa-devel] [PATCH] ALSA: ASoC: McASP: Fix data rotation for
 playback. Enables 24bit audio playback

On Fri, Jan 18, 2013 at 14:13:40, Michal Bachraty wrote:
> On Friday, January 18, 2013 08:22:53 Hebbar, Gururaja wrote:
> > On Tue, Jan 15, 2013 at 20:11:00, Michal Bachraty wrote:
> > > Signed-off-by: Michal Bachraty <michal.bachraty@...eamunlimited.com>
> > 
> > Even simple patches need a simple changelog.
> > Add a brief description about what & why it is done?
> > 
> 
> Hi Gurujaja,
> 
> > > -	u32 rotate = (32 - word_length) / 4;
> This implementation is wrong, but it works only for 16, or 32 bit audio data.
> (rotation for 16 or 32 bit is same as in code I present) Mcasp rotated data in 
> 4 bits (max value 0x7)and then masks them . That data are sended to i2s bus. 
> For 24 bit or 20 bit or other data formats, this code rotates data badly and 
> you hear somethink like noise.  You need to use
> > > +	u32 rotate = (word_length / 4) & 0x7;
> to proper data rotation. 

Correct. Now can you add the above info into the patch and re-submit. 
That way when users sees this patch, they will get all the info needed.

> 
> Regards,
> Michal
> 
> 


Regards, 
Gururaja
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