Re: dma-pool fixes

Nicolas Saenz Julienne
2020-07-31T14:15:56Z

On Fri, 2020-07-31 at 16:47 +0530, Amit Pundir wrote:
> On Fri, 31 Jul 2020 at 16:17, Nicolas Saenz Julienne

[...]

> > Ok, so lets see who's doing what and with what constraints:
>
> Here is the relevant dmesg log: https://pastebin.ubuntu.com/p/dh3pPnxS2v/

Sadly nothing out of the ordinary, looks reasonable.

I have an idea, I've been going over the downstream device tree and it seems
the reserved-memory entries, specially the ones marked with 'no-map' don't
fully match what we have upstream. On top of that all these reserved areas seem
to fall into ZONE_DMA.

So, what could be happening is that, while allocating pages for the ZONE_DMA
atomic pool, something in the page allocator is either writing/mapping into a
reserved area triggering some kind of fault.

Amir, could you go over the no-map reserved-memory entries in the downstream
device-tree, both in 'beryllium-*.dtsi' (I think those are the relevant ones)
and 'sdm845.dtsi'[1], and make sure they match what you are using. If not just
edit them in and see if it helps. If you need any help with that I'll be happy
to give you a hand.

Regards,
Nicolas

[1] You could also extract the device tree from a device running with the
downstream kernel, whatever is easier for you.