AACI broken with commit 29a4f2d3

[Takashi Iwai]

At Fri, 26 Mar 2010 21:37:51 +0530,
Philby John wrote:
> 
> On Fri, 2010-03-26 at 14:12 +0000, Catalin Marinas wrote:
> > On Fri, 2010-03-26 at 14:08 +0000, Mark Brown wrote:
> > > On Fri, Mar 26, 2010 at 01:54:45PM +0000, Catalin Marinas wrote:
> > > 
> > > > But the above says "the power down control and status register (0x26) of
> > > > the CODEC". So this refers to the AC97 registers rather than the AACI
> > > > registers. Your patch reads from the AACI registers. The AC97 registers
> > > > I think are access with aaci_ac97_(read|write) functions.
> > > 
> > > Yes, they are - but note that some CODECs will power up in low power
> > > mode and therefore attempts to read immediately after the controller
> > > probe function starts executing may fail until the controller has issued
> > > a warm reset.
> > 
> > Yes, possibly. But my point is that accessing offset 0x26 in the AACI
> > register space has nothing to do with the AC97 power register. At offset
> > 0x26 in the AACI register space you find the top part of the AACIIE2
> > register (if you can even read this as a half-word).
> > 
> >From b411099000bbbb9b076168ee98742a36018a67ac Mon Sep 17 00:00:00 2001
> From: Philby John <pjohn at in.mvista.com>
> Date: Fri, 26 Mar 2010 16:41:06 +0530
> Subject: [PATCH] Fix alignment faults on ARM Cortex introduced by commit 29a4f2d3
> 
> The commit 29a4f2d3 used writel() at offset 0x26 which is
> half-word aligned causing unaligned exceptions on a
> Cortex-A8. The original patch solved the "aaci-pl041 fpga:04:
> ac97 read back fail" issue on a soft reset. Reading from any
> arbitrary aaci register seems to solve this issue.

Then, isn't this a generic problem like PCI write-posting?


Takashi

> 
> Signed-off-by: Philby John <pjohn at mvista.com>
> ---
>  sound/arm/aaci.c |    7 +++++--
>  1 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/arm/aaci.c b/sound/arm/aaci.c
> index 656e474..91acc9a 100644
> --- a/sound/arm/aaci.c
> +++ b/sound/arm/aaci.c
> @@ -863,7 +863,6 @@ static int __devinit aaci_probe_ac97(struct aaci *aaci)
>  	struct snd_ac97 *ac97;
>  	int ret;
>  
> -	writel(0, aaci->base + AC97_POWERDOWN);
>  	/*
>  	 * Assert AACIRESET for 2us
>  	 */
> @@ -1047,7 +1046,11 @@ static int __devinit aaci_probe(struct amba_device *dev, struct amba_id *id)
>  
>  	writel(0x1fff, aaci->base + AACI_INTCLR);
>  	writel(aaci->maincr, aaci->base + AACI_MAINCR);
> -
> +	/*
> +	 * Fix: ac97 read back fail errors by reading
> +	 * from any arbitrary aaci register.
> +	 */
> +	readl(aaci->base + AACI_CSCH1);
>  	ret = aaci_probe_ac97(aaci);
>  	if (ret)
>  		goto out;
> -- 
> 1.7.0.1
> 
> 
>