[U-Boot-Users] Symptoms of a 85xx hardware problem, what could be the cause?

[robert lazarski]

On 10/11/07, robert lazarski <robertlazarski at gmail.com> wrote:
> Hi all,
>
> We've been stuck for about 3 weeks trying to run u-boot on our custom
> 8548 board. Its failing in the generic start.S code, independent of
> what TLB's we have. We've tracked this down to be hardware, but after
> much head scratching and many official support contacts, we are
> without any solid theories on the cause.
>

We found the cause, which I'm posting here in case it helps somebody
someday. The type of problem pointed to the CCB, and sure enough both
the sysclk and CCB clock were too low.

We had:

SYSCLK : 7.63 MHZ
CCB Frequency: 20 x SYSCLK = 152MHZ
E500 Frequency: 5:2 x CCB Frequency = 381.5 MHZ

That's all too low. We can at least mount the TLB's with:

SYSCLK: 17.77 MHZ
CCB Frequency : 20 x 17.77 -> 355.4 MHZ
E500 Frequency: 5/2 x CCB -> 2.5 x 355.4 -> 888.5 MHZ

Robert