From: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
To: Manuel Lauss <manuel.lauss@gmail.com>, Christoph Hellwig <hch@lst.de>
Cc: Linux-MIPS <linux-mips@vger.kernel.org>,
linux-fbdev <linux-fbdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] au1200fb: don't use DMA_ATTR_NON_CONSISTENT
Date: Tue, 23 Jul 2019 17:35:37 +0200 [thread overview]
Message-ID: <3fb07ff6-fd89-a42a-607a-1bce6a300805@samsung.com> (raw)
In-Reply-To: <CAOLZvyF0NsB6_e0=Vat48Mq1r-Qy45z509jAgQczG7RoaOqjBA@mail.gmail.com>
On 6/26/19 9:16 AM, Manuel Lauss wrote:
> On Tue, Jun 25, 2019 at 2:13 PM Christoph Hellwig <hch@lst.de> wrote:
>>
>> au1200fb allocates DMA memory using DMA_ATTR_NON_CONSISTENT, but never
>> calls dma_cache_sync to synchronize the memory between the CPU and the
>> device. If it was use on a not cache coherent bus that would be fatal,
>> but as far as I can tell from the naming and the mips platform
>> implementation it always is used in cache coherent systems. Remove
>> the DMA_ATTR_NON_CONSISTENT flag, which is a no-op in that case.
>
> Very early au1200 chips, on which this driver apparently was developed on,
> had issues with cache coherency, but this was fixed in a later step,
> none of the 3 steppings I have access to exhibit any problems
> with this patch applied.
>
>> Signed-off-by: Christoph Hellwig <hch@lst.de>
>
> Acked-By: Manuel Lauss <manuel.lauss@gmail.com>
Patch queued for v5.4, thanks.
Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics
prev parent reply other threads:[~2019-07-23 15:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-25 12:13 [PATCH] au1200fb: don't use DMA_ATTR_NON_CONSISTENT Christoph Hellwig
2019-06-26 7:16 ` Manuel Lauss
2019-07-23 15:35 ` Bartlomiej Zolnierkiewicz [this message]
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