swarren
Posts: 45
Joined: Tue Mar 01, 2016 5:56 am

RPi 3 SMMU setup documentation

Tue Mar 01, 2016 6:07 am

There's an SMMU between the ARM and VC-and-peripherals. This requires different addresses to be programmed into DMA-capable peripherals (such as USB/DWC2) vs. the ARM physical address used to access the same RAM. The mapping the VC firmware sets up is different between the RPI 0/1 and 2. Is there documentation of the mapping that the VC firmware will set up on the RPi 3?

dradford
Posts: 18
Joined: Mon Feb 15, 2016 3:33 pm

Re: RPi 3 SMMU setup documentation

Fri Mar 04, 2016 12:01 pm

The mapping had to be changed because the old one only allowed for 512MB of physical memory, so it seems reasonable to assume it will be the same as the Pi2. But that's just a guess.

swarren
Posts: 45
Joined: Tue Mar 01, 2016 5:56 am

Re: RPi 3 SMMU setup documentation

Fri Mar 04, 2016 3:08 pm

dradford wrote:The mapping had to be changed because the old one only allowed for 512MB of physical memory, so it seems reasonable to assume it will be the same as the Pi2. But that's just a guess.
That's a different issue; I'm asking about the top two bits of the ARM physical address (cache aliasing bits), not the bottom 30 bits (RAM vs. peripheral layout).

vsiles
Posts: 41
Joined: Wed Feb 04, 2015 10:04 am

Re: RPi 3 SMMU setup documentation

Fri Mar 04, 2016 7:40 pm

I recall reading (on the comments of the announce I think) that this is unchanged and that is the reason why it is still only 1Gb

dom
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 5538
Joined: Wed Aug 17, 2011 7:41 pm
Location: Cambridge

Re: RPi 3 SMMU setup documentation

Fri Mar 04, 2016 7:41 pm

Correct. The setup is identical between Pi2 and Pi3.

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