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Date: Tue, 9 Dec 2014 12:07:27 +0100
From: Arend van Spriel <arend@broadcom.com>
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To: Russell King - ARM Linux <linux@arm.linux.org.uk>
CC: Catalin Marinas <catalin.marinas@arm.com>, Arnd Bergmann <arnd@arndb.de>,
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        Will Deacon <Will.Deacon@arm.com>,
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        David Miller <davem@davemloft.net>,
        Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: using DMA-API on ARM
References: <5481794E.4050406@broadcom.com> <F51492713EF10846800D8C0ED37A7DCE01901765@SJEXCHMB15.corp.ad.broadcom.com> <F51492713EF10846800D8C0ED37A7DCE01902076@SJEXCHMB15.corp.ad.broadcom.com> <2863746.4sUSEYqahB@wuerfel> <20141208160316.GM16185@e104818-lin.cambridge.arm.com> <5485D97D.1040404@broadcom.com> <5486CCBC.3@broadcom.com> <20141209102904.GJ11285@n2100.arm.linux.org.uk>
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On 12/09/14 11:29, Russell King - ARM Linux wrote:
> On Tue, Dec 09, 2014 at 11:19:40AM +0100, Arend van Spriel wrote:
>> The issue did not trigger overnight so it seems setting bit 22<Shared
>> Attribute _Override_ Enable>  solves the issue over here. Now the question is
>> how to move forward with this. As I understood from Catalin this patch was
>> not included as it was not considered responsibility of the linux kernel.
>
> It is preferable for firmware to configure the L2 cache appropriately,
> which includes things like the prefetch offsets as well as feature bits
> like bit 22.
>
> I think what I'll do is queue up a patch which adds a warning if bit 22
> is not set, suggesting that firmware is updated to set this bit.

I was thinking in the same direction. Thanks to you all for looking into 
this. It did not feel right to use the dma_sync_single_for_cpu() for 
memory allocated with dma_alloc_coherent() and I am glad this got 
cleared up.

Regards,
Arend

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