linux-kernel - Re: [PATCH] spi: pl022: Fix broken spidev when DMA is enabled

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Message-ID: <CAMuHMdUyP-caZxTNWTTF1Z84+=RWzi673LdRbmd_Bovr_G0kqA@mail.gmail.com>
Date:	Thu, 9 Oct 2014 15:59:05 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Mark Brown <broonie@...nel.org>
Cc:	Ray Jui <rjui@...adcom.com>,
	Grant Likely <grant.likely@...aro.org>,
	linux-spi <linux-spi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	JD Zheng <jdzheng@...adcom.com>,
	Scott Branden <sbranden@...adcom.com>
Subject: Re: [PATCH] spi: pl022: Fix broken spidev when DMA is enabled

On Wed, Oct 8, 2014 at 8:21 PM, Mark Brown <broonie@...nel.org> wrote:
> On Wed, Oct 08, 2014 at 09:14:35AM -0700, Ray Jui wrote:
>> Thanks for the reply. It looks like you are also the maintainer of spidev.
>> In this case, could you please help to confirm that you expect spidev to use
>> separate buffers for TX and RX? If so, I can go ahead and make the change in
>> spidev.
>
> Yes, that would be my expectation for maximum robustness (or if it is
> going to use one buffer it explicitly maps it for mixed use but I'd
> expect that to be asking for trouble).

Having two separate buffers avoids false successes when running
"spidev_test --loop" on a buggy SPI master driver.
Been there, done that ;-)

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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