linux-kernel - Re: [PATCH] of: Add OF_DMA_DEFAULT

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Message-ID: <87mua3gb98.fsf@mpe.ellerman.id.au>
Date:   Fri, 31 Jan 2020 21:40:03 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        DTML <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>,
        Christian Zigotzky <chzigotzky@...osoft.de>,
        linuxppc-dev@...abs.org
Subject: Re: [PATCH] of: Add OF_DMA_DEFAULT_COHERENT & select it on powerpc

Ulf Hansson <ulf.hansson@...aro.org> writes:
> On Sun, 26 Jan 2020 at 12:53, Michael Ellerman <mpe@...erman.id.au> wrote:
>> There's an OF helper called of_dma_is_coherent(), which checks if a
>> device has a "dma-coherent" property to see if the device is coherent
>> for DMA.
>>
>> But on some platforms devices are coherent by default, and on some
>> platforms it's not possible to update existing device trees to add the
>> "dma-coherent" property.
>>
>> So add a Kconfig symbol to allow arch code to tell
>> of_dma_is_coherent() that devices are coherent by default, regardless
>> of the presence of the property.
>>
>> Select that symbol on powerpc when NOT_COHERENT_CACHE is not set, ie.
>> when the system has a coherent cache.
>>
>> Fixes: 92ea637edea3 ("of: introduce of_dma_is_coherent() helper")
>> Cc: stable@...r.kernel.org # v3.16+
>> Reported-by: Christian Zigotzky <chzigotzky@...osoft.de>
>> Tested-by: Christian Zigotzky <chzigotzky@...osoft.de>
>> Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
>
> Thanks Michael for helping out fixing and this! The patch looks good to me.
>
> Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>

Thanks for the review.

cheers