linux-kernel - Re: [PATCH v2] arm64: do not set dma masks that device connection can't handle

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Message-ID: <24c5a31e-0148-315b-19b3-0aec456e1164@cogentembedded.com>
Date:   Tue, 10 Jan 2017 17:01:58 +0300
From:   Nikita Yushchenko <nikita.yoush@...entembedded.com>
To:     Robin Murphy <robin.murphy@....com>,
        Will Deacon <will.deacon@....com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        linux-arm-kernel@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        Simon Horman <horms@...ge.net.au>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        artemi.ivanov@...entembedded.com, fkan@....com
Subject: Re: [PATCH v2] arm64: do not set dma masks that device connection
 can't handle

>> What issue "IOMMU doesn't solve"?
>>
>> Issue I'm trying to address is - inconsistency within swiotlb
>> dma_map_ops, where (1) any wide mask is silently accepted, but (2) then
>> mask is used to decide if bounce buffers are needed or not. This
>> inconsistency causes NVMe+R-Car cobmo not working (and breaking memory
>> instead).
> 
> The fundamental underlying problem is the "any wide mask is silently
> accepted" part, and that applies equally to IOMMU ops as well.

Is just posted version better?

It should cover iommu case as well.

Nikita