linux-kernel - Re: [PATCH] dma-pool: use single atomic pool for both DMA zones

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Date:   Wed, 8 Jul 2020 17:36:35 +0200
From:   Christoph Hellwig <hch@....de>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Cc:     Jeremy Linton <jeremy.linton@....com>,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        David Rientjes <rientjes@...gle.com>,
        linux-rpi-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dma-pool: use single atomic pool for both DMA zones

On Wed, Jul 08, 2020 at 12:35:34PM +0200, Nicolas Saenz Julienne wrote:
> > Which allows me to switch between ACPI/DT on the machine. In DT mode it 
> > works fine now, 
> 
> Nice, would that count as a Tested-by from you?
> 
> > but with ACPI I continue to have failures unless I 
> > disable CMA via cma=0 on the kernel command line. 
> 
> Yes, I see why, in atomic_pool_expand() memory is allocated from CMA without
> checking its correctness. That calls for a separate fix. I'll try to think of
> something.

I think we need a dma_coherent_ok for the allocations from the
pool and then fall back to the next better one to get started.  And
yes, CMA is a bit of a mess, that generally needs better checks.