linux-kernel - Re: [RESEND2 PATCH 0/3] Fix kernel panic in dma-coherent

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Date:	Mon, 8 Feb 2016 18:04:19 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	Robin Murphy <robin.murphy@....com>
Cc:	Brian Starkey <brian.starkey@....com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org,
	Michal Nazarewicz <mina86@...a86.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dan Williams <dan.j.williams@...el.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RESEND2 PATCH 0/3] Fix kernel panic in dma-coherent

On Mon, Feb 08, 2016 at 05:59:25PM +0000, Robin Murphy wrote:
> Hi Mark,
> 
> On 08/02/16 17:50, Mark Rutland wrote:
> >On Mon, Feb 08, 2016 at 05:30:49PM +0000, Brian Starkey wrote:
> >>Hi,
> >>
> >>I'm resending these again to try and garner some interest. Without
> >>this series, dma-coherent cannot be used on arm64 platforms.
> >
> >I think you need to characterize that a bit better. I see plenty of
> >instances of 'dma-coherent' in dts files, assuming you mean the DT
> >dma-coehrent property.
> >
> >If not, feel free to stop reading now.
> 
> Terminology overload: the dma-coherent DT property is about devices
> having cache-coherent access to system memory within the linear map.
> The dma-coherent thing here is pretty much the precise opposite of
> that - namely creating CPU mappings for memory which belongs to the
> device itself and may be behind an I/O bus (e.g. a framebuffer on a
> video card).

Phew.

Sorry for the noise, and thanks for setting me straight!

Mark.