[bug report] staging: add bcm2708 vchiq driver

Eric Anholt eric at anholt.net
Wed Nov 16 10:23:27 PST 2016

Michael Zoran <mzoran at crowfest.net> writes:

> On Tue, 2016-11-15 at 22:04 -0500, Vince Weaver wrote:
>> On Tue, 15 Nov 2016, Michael Zoran wrote:
>> > I'm still interested to know more about the MMU statement.  I would
>> > think at least some of the RPI models have one because swapping
>> > appears
>> > to be at least somewhat functional on the later models.
>> All Raspberry Pi models have an MMU.  I'm not sure why anyone thinks 
>> otherwise.
>> Though just to be pedantic, you don't need an MMU to "swap".  In
>> general 
>> you do to "page".
>> Vince
> From the BCM2835 doc floating around the web the RPI should have 2
> MMUs.  One on the VC side and one on the ARM side.  Since we are being
> pedantic here, I'll ask the question this way.
> Do all RPIs has an enabled MMU on the ARM side and do all RPIs support
> paging?

Yes.  The MMU between ARM's virtual and ARM's physical memory addresses
is always present and is totally normal.  The second MMU maps between
ARM's physical and bus, and is too coarse to be of much use so it's
almost a 1:1 mapping.

When people talk about RPi lacking an MMU, they're talking about between
devices (such as the 3D engine, video decode/encode, VPU, etc.) and
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