Linux on PPC

[Steve Strublic]

> -----Original Message-----
> From: linuxppc-embedded-bounces+sstrublic=hypercom.com at ozlabs.org
> [mailto:linuxppc-embedded-bounces+sstrublic=hypercom.com at ozlabs.org]
On
> Behalf Of David Hawkins
> Sent: Friday, March 03, 2006 1:07 PM
> To: Rune Torgersen
> Cc: linuxppc-embedded at ozlabs.org
> Subject: Re: Linux on PPC
> 
> 
> >>Right, thats I made sure to say; Physical Memory Map.
> >>
> >>For example, on the Artesyn manual on their PrPMC they give a
> >>physical memory map, and in the Yosemite board, there is a
> >>physical memory map. I know many of the memory areas can be
> >>redefined in hardware to have a different memory location, but
> >>its still a physical address.
> >>
> >
> > Still not right. Even the physical memory is software settable. What
> > matters is what chip-select things are hooked up to, and then map
those
> > chip selects correctly (size, base address, access with and so on)
> 
> Hi Rune,
> 
> Thanks for responding.
> 
> Thats what I meant with 'redefined in hardware'. But yes, redefined
> up to the limit of the wiring on the board of course (chip-selects
> and bus widths). That's where having the board schematic is
> invaluable.
> 
> But ok, I'm pretty sure I get the point, and hopefully the
> original poster understands a bit more too.
> 
> Given a board that you expect to run Linux on, I would imagine
> you would select hardware settings consistent with making
> Linux happy, i.e., defining 'in software' (the bootloader)
> the physical address map (eg. like the Embedded Planet reference
> manual for the 440EP Yosemite board), and then setup U-Boot and
> Linux to program the TLBs to translate to those same addresses.
> 
> When looking at the Yosemite board, I booted U-Boot and compared
> device dcr settings to the recommended ones in the EP manual. Then
> when I booted Linux, I took a look and found that on the whole, Linux
> didn't touch too much of the things setup by U-Boot, i.e., the
> responsibility for setting up the Linux environment was mainly
> the job of the bootloader.
> 
> So, if I had a board with a custom bootloader, I would be
> concerned that the bootloader might not know enough about
> Linux, to setup the hardware correctly.

The boot loader should, ideally, NOT know anything about Linux except
for knowing that since a Linux is being loaded, it requires some
information at boot time, and the format in which to provide said
information.

Steve

> 
> Does that sound right?
> 
> Dave
> 
> 
> 
> 
> 
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