Re: [PATCH for-4.14 0/3] Remove the 1GB limitation on Rasberry Pi 4

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 19 May 2020, Tamas K Lengyel wrote:
> On Tue, May 19, 2020 at 11:23 AM Julien Grall <julien@xxxxxxx> wrote:
> >
> >
> >
> > On 19/05/2020 04:08, Tamas K Lengyel wrote:
> > > On Mon, May 18, 2020 at 5:32 AM Julien Grall <julien@xxxxxxx> wrote:
> > >>
> > >> From: Julien Grall <jgrall@xxxxxxxxxx>
> > >>
> > >> Hi all,
> > >>
> > >> At the moment, a user who wants to boot Xen on the Raspberry Pi 4 can
> > >> only use the first GB of memory.
> > >>
> > >> This is because several devices cannot DMA above 1GB but Xen doesn't
> > >> necessarily allocate memory for Dom0 below 1GB.
> > >>
> > >> This small series is trying to address the problem by allowing a
> > >> platform to restrict where Dom0 banks are allocated.
> > >>
> > >> This is also a candidate for Xen 4.14. Without it, a user will not be
> > >> able to use all the RAM on the Raspberry Pi 4.
> > >>
> > >> This series has only be slighlty tested. I would appreciate more test on
> > >> the Rasbperry Pi 4 to confirm this removing the restriction.
> > >
> > > Hi Julien,
> >
> > Hi,
> >
> > > could you post a git branch somewhere? I can try this on my rpi4 that
> > > already runs 4.13.
> >
> > I have pushed a branch based on unstable and the v2 of the series:
> >
> > git://xenbits.xen.org/people/julieng/xen-unstable.git
> >
> > branch arm-dma/v2
> >
> 
> I've updated my image I built with
> https://github.com/tklengyel/xen-rpi4-builder a while ago and I've
> defined 2048m as total_mem and Xen seems to be booting fine and passes
> execution to dom0. With 512m being set as the Xen cmdline for dom0_mem
> it was working. When I increased the mem for dom0 the boot is now
> stuck at:
> 
> [    1.427788] of_cfs_init
> [    1.429667] of_cfs_init: OK
> [    1.432561] clk: Not disabling unused clocks
> [    1.437239] Waiting for root device /dev/mmcblk0p2...
> [    1.451599] mmc1: queuing unknown CIS tuple 0x80 (2 bytes)
> [    1.458156] mmc1: queuing unknown CIS tuple 0x80 (3 bytes)
> [    1.464729] mmc1: queuing unknown CIS tuple 0x80 (3 bytes)
> [    1.472804] mmc1: queuing unknown CIS tuple 0x80 (7 bytes)
> [    1.479370] mmc1: queuing unknown CIS tuple 0x80 (3 bytes)
> [    1.546902] random: fast init done
> [    1.564590] mmc1: new high speed SDIO card at address 0001
> 
> Could this be because the DTB I compiled from a fresh checkout of
> https://github.com/raspberrypi/linux.git branch rpi-4.19.y whereas the
> kernel itself is from a checkout ~5 months ago? I guess that must be
> the cause because even if I decrease the dom0_mem to 512m it still
> gets stuck at the same spot whereas it was booting fine before.

Just so that you are aware, there is a known issue with setting dom0_mem
greater than 512M. I have a WIP patch to fix it in Linux that I plan to
send to the list soon.