[PATCH] ARM: Versatile Express: Add default memory layout
Catalin Marinas
catalin.marinas at arm.com
Thu Jul 22 07:40:23 EDT 2010
On Thu, 2010-07-22 at 12:30 +0100, Russell King - ARM Linux wrote:
> On Thu, Jul 22, 2010 at 12:19:56PM +0100, Catalin Marinas wrote:
> > On Thu, 2010-07-22 at 12:16 +0100, Russell King - ARM Linux wrote:
> > > The kernel boot requirements document has for the last _8_ years said:
> > >
> > > The boot loader must pass at a minimum the size and location of the system
> > > memory, and root filesystem location. Therefore, the minimum tagged list
> > > should look:
> > >
> > > +-----------+
> > > base -> | ATAG_CORE | |
> > > +-----------+ |
> > > | ATAG_MEM | | increasing address
> > > +-----------+ |
> > > | ATAG_NONE | |
> > > +-----------+ v
> > >
> > > and still u-boot gets it wrong... Now tell me why I hate boot loaders
> > > soo much.
> >
> > Maybe it's time to ignore all boot loaders and do everything in the
> > kernel :)
>
> Maybe, but then we can never do things like pass command line arguments
> to the kernel, or discover where system RAM is, etc.
I should have rephrased/clarified 'ignore'. It's more like ignoring
incomplete information coming from the bootloader and using sane
defaults in the kernel.
Anyway, I don't think it's worth arguing much here, we've been living
with this issues for many years.
> It's also an argument for avoiding DT! If boot loaders can't even get
> the most basic of information right...
With DT I see it as slightly different. The DT information is provided
by the board manufacturer and the boot loader doesn't need to do much
discovery. It can be a pretty dumb boot loader just passing the relevant
DT address to the kernel. But that's another thread of discussion (which
unfortunately I didn't have time to follow properly).
--
Catalin
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