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Re: [Qemu-ppc] PPC440 bus frequencies and timers

From: luigi burdo
Subject: Re: [Qemu-ppc] PPC440 bus frequencies and timers
Date: Tue, 13 Mar 2018 15:17:43 +0000

Hi Zoltan,

check in the patched uboot if this utility is included. i found this message in mos forum

Edit: Acube has a nice utility to check the reference clock (checkbaseclock). It's included with the new version of uboot. I just executed this utility again, and indeed it says my sam has a 50 Mhz. clock.


Da: Qemu-ppc <qemu-ppc-bounces+address@hidden> per conto di BALATON Zoltan <address@hidden>
Inviato: martedì 13 marzo 2018 13:35
A: address@hidden
Oggetto: [Qemu-ppc] PPC440 bus frequencies and timers

Anyone here with knowledge about PPC440 (especially as used in AMCC460EX
SoC that the Sam460ex board is built on)? I see some problems related to
timers and bus frequencies which are likely not emulated correctly but I
don't know what's wrong or missing.

Problems I know about that may be related:

1. System time is going slower than expected in AROS (can be seen e.g. in
Time Prefs). The seconds advance but much slower than they should. (AROS
boot iso can be downloaded from http://aros.sourceforge.net/nightly1.php)

2. I had to set clock multipliers in SDR0_STRP0 register (that seems to
have values for different internal buses of the SoC such as PLB and OPB)
in qemu/hw/ppc/ppv440_uc.c:396 to 0 instead of a value more closely
matching real hardware (although I'm not sure what real hardware has in
this reg) because if I set the bits in comment for multipliers bus
frequencies are printed correctly but this slows down U-Boot. A 0 value
here works for U-Boot but makes the printed bus frequencies wrong. (I've
also come across this u-boot patch
https://lists.denx.de/pipermail/u-boot/2011-July/096848.html but haven't
yet tried if it makes any difference.)

3. AmigaOS 4 boots very slowly which may be related as there seem to be a
delay in IO operations (similar to U-Boot with non-0 value in STRP0) that
could be because of a timer going slower than expected but I'm not sure
without source what it really does. (There also seem to be graphics
corruption issues with AmigaOS 4 but I could not identify yet if these are
becuase of incomplete emulation of the SM502 chip or some other problem
caused by delays due to timing (as writing SM502 registers seem to have a
much longer delay than expected).

4. Linux kernel boots but hangs just before init should start. I'm not
sure how to debug this to find out where's the problem so I'm not sure
it's related but could be.

So there seems to be a problem with tb and other frequencies and timers
relying on these but I don't know what's on real hardware and how exactly
are these emulated in QEMU. Does anyone know more about these registers
and how it works on real hardware and has any hints what could be the
problem here? Any help is appreciated.


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