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From: Boris Brezillon <boris.brezillon@bootlin.com>
To: Ladislav Michl <ladis@linux-mips.org>
Cc: linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org,
	Boris Brezillon <boris.brezillon@free-electrons.com>,
	Peter Ujfalusi <peter.ujfalusi@ti.com>,
	Roger Quadros <rogerq@ti.com>,
	Aaro Koskinen <aaro.koskinen@iki.fi>,
	Tony Lindgren <tony@atomide.com>,
	"H. Nikolaus Schaller" <hns@goldelico.com>,
	Andreas Kemnade <andreas@kemnade.info>
Subject: Re: [PATCH v2] mtd: onenand: omap2: Disable DMA for HIGHMEM buffers
Date: Fri, 20 Apr 2018 22:01:34 +0200	[thread overview]
Message-ID: <20180420220134.3021860f@bbrezillon> (raw)
In-Reply-To: <20180416065256.GA24455@lenoch>

Hi Ladislav,

On Mon, 16 Apr 2018 08:52:59 +0200
Ladislav Michl <ladis@linux-mips.org> wrote:

> dma_map_single doesn't get the proper DMA address for vmalloced area,

That's not true, it returns the right DMA (physical) address, it's just
that:

1/ the memory location is not necessarily physically contiguous
2/ in case your arch is VIVT ot VIPT, there may be several entries in
   the cache pointing to the same physical location, and the cache
   maintenance operations done by dma_map_single() will only operate on
   one of these entries.

> so disable DMA in this case.
> 

The fix looks good though. Can you rephrase your commit message to make
it clearer.

Thanks,

Boris

  parent reply	other threads:[~2018-04-20 20:01 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-16  6:52 [PATCH v2] mtd: onenand: omap2: Disable DMA for HIGHMEM buffers Ladislav Michl
2018-04-16 11:34 ` Peter Ujfalusi
2018-04-16 13:32   ` Ladislav Michl
2018-04-20 20:01 ` Boris Brezillon [this message]
2018-05-02  8:06   ` Ladislav Michl
2018-05-02  9:16     ` Boris Brezillon

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