Subject: Re: Fw: Unable to write registers to enable USB clock on SA-1111 board

From: John G Dorsey <[email-masked]>
Date: Wed, 02 Aug 2000 13:44:52 -0400

Arjan Opmeer wrote:

> >> >SKPCR |= SKPCR_UCLKEN;
> >> >printk("SKPCR: %x\n", SKPCR);
> >>
> >> This is displaying 0?
> >
> >Ahem, jupz, it sure does.

I have no explanation for this, but you're right, with 2.4.0-test5-rmk1-np1,
my reads of the SKPCR return zero as well. (Disclaimer: I tossed a single
write/read into sa1111_init() immediately after enabling the RAB clock; this
is hardly conclusive.) Other registers in the System Controller seem to be
okay.

However, I've been playing around with the SA-1111 Serial Audio Controller
recently, which also relies on the SKPCR, and have not seen this problem on a
suitably-patched (2.4.0-test5-rmk1-np1-jd1) kernel. This patch is _very_
alpha, but I thought I'd put it up before I go on vacation in case anyone
wants to tinker with it. It's in the "Bleeding Edge" section of:

  http://www.cs.cmu.edu/~wearable/software/assabet.html

If you're willing to tolerate the occasional DMA lockup or weird audio
corruption, this is the driver for you. =)

Arjan, for your USB work, you might try just adding the parts of the patch
which set up the shared memory controller and enable the DMA clock.

-jd

unsubscribe: body of `unsubscribe linux-arm' to [email-masked]
++        Please use [email-masked] for           ++
++                        kernel-related discussions.                      ++

---

From: Stuart Adams <[email-masked]>
Date: Wed, 02 Aug 2000 20:42:50 -0400

> corruption, this is the driver for you. =)

 FYI - be sure to check the errata in the
 latest SA1111 spec update - something is broken in the way the SA1111
 DMA's stuff from itself to SDRAM - there are specific memory regions
 where DMAing data to that region will corrupt memory

-- Stuart