Subject: RE: booting kernel on SA1110

From: Jeff Sutherland <[email-masked]>
Date: Thu, 27 Apr 2000 17:04:34 -0400

> 	Is it possible to test for this by NOT enabling the 
> Icache at this
> point in head-armv.S?  Or will that blow up for other reasons?
> 
> Thanks,
> Chris

Normally you should always try to run with the Icache on for performance
reasons, even (nay, especially) when running from rom.  It doesn't need the
MMU.  If your system won't run from DRAM with the Icache on and you think
the memory timing is correct, reduce the speed of the cpu to something like
118MHz, redo your timing calculations, and try again.  SDRAM timing setup is
not trivial on the SA1110.  If it won't run even at the lowest cpu clock
frequency when you turn on the Icache it's time to revise the circuit board
layout (or review the specs for your memory).  Signal integrity is a major
issue with these fast low power processors.  Even on the Intel Assabet
(SA1110 development platform) about 132MHz is all the faster this thing will
run reliably day in and day out.  At faster speeds we experience occasional
random lockups.  Happens to WindowsCE, too, so it's not just a Linux
thing...

//Jeff

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From: Nicolas Pitre <[email-masked]>
Date: Thu, 27 Apr 2000 19:06:59 -0400 (EDT)

> random lockups.  Happens to WindowsCE, too, so it's not just a Linux

Didn't happen to me in Linux even at 200MHz, so maybe it's a WindowsCE
thing...   :-)

Nicolas

---

From: Erik Mouw <[email-masked]>
Date: Fri Apr 28 14:15:46 +0200 (MDT) 2000

On Thu, 27 Apr 2000 17:04:34 -0400, Jeff Sutherland wrote:
[snip]

> random lockups.  Happens to WindowsCE, too, so it's not just a Linux

Sounds like bad memory timings to me. We got the same symptoms when we
overclocked an SA1100 without adjusting the DRAM timings. On the SA1100
the DRAM timings are closely related to the core clock speed. If the
SA1110 uses the same mechanism, you should just recalculate and set the
DRAM timings for the higher clock speed.

Erik

-- 
J.A.K. (Erik) Mouw, Information and Communication Theory Group, Department
of Electrical Engineering, Faculty of Information Technology and Systems,
Delft University of Technology, PO BOX 5031,  2600 GA Delft, The Netherlands
Phone: +31-15-2783635  Fax: +31-15-2781843  Email: [email-masked]
WWW: http://www-ict.its.tudelft.nl/~erik/