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...@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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