[U-Boot] [PATCH] lib: Add CONFIG_FDT_IGNORE_FIXUP_MEMORY_NODE

[Tom Rini <trini@ti.com>]

On Tue, Apr 08, 2014 at 03:05:36PM +0200, Wolfgang Denk wrote:
> Dear Nobuhiro,
> 
> In message <CABMQnV+k+Rmx7E8o-nfBpYg5-nWrXi6Oz_+BCYs-vDNdv_z-rw@mail.gmail.com> you wrote:
> > 
> > > Please explain why you would want to do this.  To me it makes no
> > > sense.  Either U-Boot knows the correct memory size, then it should
> > > pass it to Linux.  Or it does not, then U-Boot should be fixed.
> > 
> > For example, I can access the memory of all in the U-Boot, but I may
> > want to control
> > the highmem on Linux,I do not want to show a specific area from kernel
> > and userland.
> 
> Is it not sufficient to pass some "mem=" boot argument?  We even have
> automatic support for this in U-Boot (see the CONFIG_PRAM feature).

There's various ways to do this, yes.  But it doesn't cover the >4GB
case.

> > > Also, I object that your implementation is ARM specific.  If such a
> > > feature gets added, it should be architecture independent.
> > 
> > I see. But arch_fixup_memory_node() is used by ARM only.
> > So, we see to be dependent on the ARM is only this.
> 
> All architectures that support the device tree update the memory size
> for Linux, so we should find a generic way to handle this.  Actually
> we should always strive to reduce this arhitecture specific code.

Note that ARM provides arch_fixup_memory_node to make sure we have all
of the bank information populated and then calls fdt_fixup_memory_banks,
while PowerPC just calls fdt_fixup_memory which calls banks with a '1'
for number of banks.  MIPS (and everyone else) isn't doing anything
about this atm, but probably should.

At the high level, we need to see if we _really_ do need to be using
arch_fixup_memory_node at all because my gut feeling is (a) we've
already always filled in the bank info and if not (b) that is a bug to
correct.  But I haven't dived in to the relevant code here yet.

-- 
Tom
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