[PATCH 2/2 v2] sound/soc: mpc5200_psc_ac97: Use gpio pins for cold reset.

[Grant Likely]

On Wed, Jun 9, 2010 at 9:39 AM, Eric Millbrandt
<emillbrandt at dekaresearch.com> wrote:
> The implementation of the ac97 "cold" reset is flawed.  If the sync and
> output lines are high when reset is asserted the attached ac97 device
> may go into test mode.  Avoid this by reconfiguring the psc to gpio mode
> and generating the reset manually.

Hi Eric,

Thanks for the patch.  Given a) that this is essentially a silicon
bug, b) that AC97 only works on PSCs 1 & 2 which cannot be relocated
to different pins, c) that I really want to avoid giving drivers
access to port_config even through an API, and d) All mpc5200 AC97
systems will probably have the same issue, I think this is something
that shouldn't require a change to the device tree, and can probably
be contained within arch/powerpc/platforms/52xx.

Overall, I have no problem with the function of the change, but I'd
like to see these two changes:
- Add a helper function ot arch/powerpc/platforms/52xx to perform an
AC97 reset using GPIOs (select GPIO in port_config, toggle reset,
select PSC in port_config).  Something like
mpc5200_psc_ac97_gpio_reset(int psc_number).  Just move the GPIO bits.
 The PSC mode setting can be left in the driver.
- Go ahead and hardcode the GPIO numbers into the platform code.  It
is definitely a hardware bug workaround, and it isn't something that
would normally be described in the device tree (though you probably
need to make the gpio_lock spinlock non-static to maintain mutual
exclusion).

g.