Lockups reading from i.MX51 SSI registers

[Sascha Hauer]

On Fri, Aug 10, 2012 at 10:14:56PM +0200, Uwe Kleine-König wrote:
> Hi,
> 
> On Fri, Aug 10, 2012 at 09:56:38PM +0200, Sascha Hauer wrote:
> > On Fri, Aug 10, 2012 at 08:50:08PM +0100, Mark Brown wrote:
> > > I'm trying to use -next to test AC'97 register I/O on an i.MX51 board
> > > but I'm seeing the CPU hang during probe at:
> > > 
> > > 	lreg = (reg & 0x7f) <<  12 ;
> > > 	writel(lreg, base + SSI_SACADD);
> > > 
> > > in imx_ssi_ac97_read().  I'm somewhat suspicious this might be because
> > > the IP block isn't clocked properly, I do notice the recent conversion
> > > to the clock API which looks rather involved but it's possible something
> > > else broke.  Does anyone have any bright ideas what might be going on
> > > here?  The board doesn't have the reste functions defined so this is the
> > > first interaction with the hardware block AFAICT.
> > 
> > No idea currently, just adding Uwe to Cc because I think he has seen
> > something similar on an i.MX35 board recently.
> I havn't debugged that yet, but one issue I think needs to be solved is
> that since the clk conversion there are two ssi clocks. And from a quick
> look the ssi driver only handles one of them.

One clock is for the bus which must be turned on. The other is for the
bitclock which we currently can ignore since we only support clock slave
mode.
On an i.MX5 ssi[123]_ipg_gate must be turned on by the ssi driver. From
a quick look to the clock code it looks correct.

Sascha


-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |