[alsa-devel] [PATCH] ASoC: sgtl5000: Do not read registers prior to turning on the supplies

[Marek Vasut]

Hello Fabio,

> Hi Marek,
> 
> (Sorry for the top-posting here)
> 
> There is a delay of 23 seconds, which is 1 second for each sgtl500-
> register write.
> 
> This is an I2C issue and we have already talked about this on the
> linux-arm-kernel list.
> 
> Alexandre Belloni also sees this 1 second on another I2C device connected
> to mx28.

There was no problem without these patches though. With your patches, I see NAK 
happening on the I2C lines upon first 2-byte write.

> Regards,
> 
> Fabio Estevam
> ________________________________________
> From: Marek Vasut [marex at denx.de]
> Sent: Thursday, May 30, 2013 5:36 PM
> To: alsa-devel at alsa-project.org
> Cc: Mark Brown; Estevam Fabio-R49496
> Subject: Re: [alsa-devel] [PATCH] ASoC: sgtl5000: Do not read registers
> prior to turning on the supplies
> 
> Hi Mark, Fabio,
> 
> > On Tue, May 28, 2013 at 11:04:18AM -0300, Fabio Estevam wrote:
> > > Commit b871f1ad (ASoC: sgtl5000: Read SGTL5000_CHIP_ID in i2c_probe())
> > > placed the code for reading the codec revision prior to turning on the
> > > power supplies.
> > > 
> > > Even though this works on some systems that always have the codec power
> > > supplies enabled, this is not correct, so revert this commit.
> > 
> > It seems like a better fix for this is to just enable the supplies while
> > doing the device identification?
> 
> This patch does kinda fix it for me, but the system takes quite some time
> to init the soundcard now (a few seconds). After reverting these two
> patches, the soundcard works just fine (like before):
> 
>     ASoC: sgtl5000: Fix driver probe after reset
>     ASoC: sgtl5000: Read SGTL5000_CHIP_ID in i2c_probe()
> 
> Best regards,
> Marek Vasut

Best regards,
Marek Vasut