[PATCH v2 2/3] arm/dt: tegra: add dts file for paz00

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

On Fri, Oct 28, 2011 at 09:49:49AM -0700, Stephen Warren wrote:
> When boards boot from DT, there is no fixup function to override the
> bootloader's ATAGs. I also see a bunch of code to set up the memory
> information from DT e.g. setup_machine_fdt()'s call to:
> 
> 	of_scan_flat_dt(early_init_dt_scan_memory, NULL);
> 
> ... but I assume that happens before the ATAGs are processed, and the
> buggy ATAGs end up overriding the information in the DT file.

As far as the uncompressed kernel is concerned, there is either ATAG
or DT information, never both.  If the boot loader provides ATAGs and
the zImage has a DT appended to it, the zImage decompressor merges the
ATAGs into the appended DT and passes the DT to the kernel.

So anyone who currently 'fixes' their broken boot loader via the fixup
function by directly manipulating the ATAGS is going to hit the DT
image instead.

> > I've seen patches on the chromeos tree which try to reserve the gpu
> > memory on demand. While we are at it, what is the vmalloc=192M used
> > by most other boards for?
> 
> I'm not sure what vmalloc= does exactly. I somewhat doubt it's necessary
> until we have code that uses the GPU in mainline.

It defines the size of the vmalloc and ioremap area - and limits the
maximum amount of low memory (non-highmem) available to the kernel to
achieve the specified size of the vmalloc area.  Any additional memory
will be discarded, or in the presence of a highmem enabled kernel, will
be turned into highmem.