Re: MIPS/CI20: BUG: Bad page state

[Paul Burton <paul.burton@mips.com>]

Hi Aaro,

On Wed, Apr 24, 2019 at 11:40:55PM +0300, Aaro Koskinen wrote:
> On Wed, Apr 24, 2019 at 07:29:29PM +0000, Paul Burton wrote:
> > On Wed, Apr 24, 2019 at 09:20:12PM +0300, Aaro Koskinen wrote:
> > > I have been trying to get GCC bootstrap to pass on CI20 board, but it
> > > seems to always crash. Today, I finally got around connecting the serial
> > > console to see why, and it logged the below BUG.
> > > 
> > > I wonder if this is an actual bug, or is the hardware faulty?
> > > 
> > > FWIW, this is 32-bit board with 1 GB RAM. The rootfs is on MMC, as well
> > > as 2 GB + 2 GB swap files.
> > > 
> > > Kernel config is at the end of the mail.
> > 
> > I'd bet on memory corruption, though not necessarily faulty hardware.
> > 
> > Unfortunately memory corruption on Ci20 boards isn't uncommon... Someone
> > did make some tweaks to memory timings configured in the DDR controller
> > which improved things for them a while ago:
> > 
> >   https://github.com/MIPS/CI20_u-boot/pull/18
> > 
> > Would you be up for testing with those tweaks? I'd be happy to help with
> > updating U-Boot if needed.
> 
> Thanks, I wasn't aware of this, and seems like it could help.
> 
> I guess instructions here <https://elinux.org/CI20_Dev_Zone> are valid,
> i.e. I can use MMC/SD card to re-flash the U-boot without the risk of
> bricking the board, if I understood correctly?

Yes that's correct. It's difficult to impossible to totally brick the
board, given the ability to boot from SD or USB & rewrite the NAND.

One option would be to just build the new U-Boot for SD boot, and leave
your NAND U-Boot entirely untouched until/unless you're satisfied that
the changes help.

> BTW, would it be possible to re-adjust these timings from the kernel side?

Maybe, I'm really not sure. So long as it can be done without destroying
any of the RAM content it would be OK, but I don't know if that's the
case.

> > Do you know which board revision you have? (Is it square or a funny
> > shape, green or purple, and does it have a revision number printed on
> > the silkscreen?)
> 
> It's a purple one. Based on quick look all printings are identical to this
> one:
> https://images.anandtech.com/doci/8958/purple%20ci20_smaller_678x452.jpg

OK good to know - so it's a revision B board, which changed from Hynix
to Samsung DDR:

  https://elinux.org/CI20_Hardware#Board_Revisions_and_changes

That's also the revision Gabriele who submitted the U-Boot pull request
linked above has.

Thanks,
    Paul