Re: [REGRESSION] tegra124: nyan-big: LPAE not working

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On Mon, Feb 11, 2019 at 09:20:33AM +0000, Tristan Bastian wrote:
> 
> Thierry Reding – Mon, 11. February 2019 9:52
> > On Sun, Feb 10, 2019 at 08:53:11PM +0100, Tristan Bastian wrote:
> > > Thierry, do you have any news on this?
> > > 
> > > I don't think, that google is going to push an updated version of coreboot
> > > to each nyan-big device..
> > > So reverting this patch at least for the nyan devices would be the best I
> > > think..
> > 
> > Yes, I agree. I had a brief chat with Rob Herring about this and he too
> > agrees that we should revert it for now. I'll make it a manual revert
> > and add a comment to the device tree node that will hopefully avoid any
> > future janitorial "cleanups" of this sort.
> 
> great news! :)
> 
> > > BTW: I'm now running u-boot natively and it seems like u-boot always has a
> > > problem with the memory..
> > > If u-boot is used chainloaded to coreboot it is only getting 2GB of memory
> > > and running u-boot natively also just gives me 2GB..
> > > I've tested that with a kernel with "ARM: tegra: Fix unit_address_vs_reg DTC
> > > warnings for /memory" reverted and also on a kernel, before this patch was
> > > applied..
> > 
> > It's possible that U-Boot doesn't support LPAE and therefore may not be
> > able to use more than the 2 GiB of memory.
> 
> So I at least enabled LPAE in u-boot with "CONFIG_ARMV7_LPAE=y" and
> this was for some reason also needed to get some output on the
> display..
> I'm not sure why LPAE needs to activated in u-boot for display output
> on the nyan-big..
> Without LPAE enabled u-boot was still working, and booted linux, but
> u-boot didn't display anything on screen, linux then did..

Yeah, that's surprising. Perhaps without LPAE U-Boot thinks there's not
enough memory for the framebuffer? There should be plenty, so maybe
there is something else going on here.

> > However, U-Boot should be
> > able to tell the kernel exactly how much memory the system has and pass
> > that on via device tree. That still does work, right?
> 
> It seems like this is not working..
> And this seems to be the case with both, u-boot chainloaded and
> running u-boot natively..
> 
> I've used these scripts for flashing:
> https://github.com/NVIDIA/tegra-uboot-flasher-scripts
> And used the norrin device since it seems like it is the nyan-big dev
> board?
> But going with the norrin device config should not be the issue here
> since the problem also exists when chainloading u-boot, right?

It could be a problem. The memory bank configuration is stored in what's
called a BCT along with a bunch of other parameters that define what the
memory controller needs to access the given memory chips. So if you've
flashed a BCT that's for a board with only 2 GiB of memory you would end
up with a system that can't address any more than that. It's somewhat
surprising that memory accesses work at all with a BCT that's for
different memory chips, but sometimes you can get lucky.

You may want to try reflashing with the right BCT. The simplest would
probably be to duplicate the cbootimage configuration for Norrin and
substitute the relevant bits by what you have from the Chromebook flash
utilities. Looks like the BCT in really the only thing you can replace
there. Make sure to replace it with the one that matches your Chromebook
and it should give you the right memory bank configuration.

> Simon Glass used his servo board to enter the tegrarcm mode:
> https://patchwork.ozlabs.org/patch/1019003/
> 
> I had to erase the internal SPI flash in order to boot into the
> tegrarcm mode.. 
> Do you have some instructions or internal documentation to tell me, if
> some of the unpopulated buttons on the nyan-big mainboard can be used
> to enter the tegrarcm state?

You should be able to boot into recovery mode with the "enterrcm"
command in U-Boot. I'm not aware of any buttons on the mainboard that
can be used for this, unfortunately.

Thierry

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