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

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Message-ID: <21a7276e98ae245404d82537ac1ee597a92f9150.camel@suse.de>
Date:   Wed, 08 Jul 2020 12:35:34 +0200
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     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>
Cc:     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

Hi Jim,

On Tue, 2020-07-07 at 17:08 -0500, Jeremy Linton wrote:
> Hi,
> 
> I spun this up on my 8G model using the PFTF firmware from:
> 
> https://github.com/pftf/RPi4/releases
> 
> 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.

> It think that is because
> 
> using DT:
> 
> [    0.000000] Reserved memory: created CMA memory pool at
> 0x0000000037400000, size 64 MiB
> 
> 
> using ACPI:
> [    0.000000] cma: Reserved 64 MiB at 0x00000000f8000000
> 
> Which is AFAIK because the default arm64 CMA allocation is just below 
> the arm64_dma32_phys_limit.

As I'm sure you know, we fix the CMA address trough DT, isn't that possible
trough ACPI?

Regards,
Nicolas


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