linux-kernel - Re: [PATCH v2] ARM: dts: imx6dl: disable dma support for spi on i.mx6dl

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Date:	Tue, 16 Sep 2014 09:43:06 +0800
From:	Shawn Guo <shawn.guo@...escale.com>
To:	Lucas Stach <l.stach@...gutronix.de>
CC:	Robin Gong <b38343@...escale.com>, <kernel@...gutronix.de>,
	<robh+dt@...nel.org>, <pawel.moll@....com>, <mark.rutland@....com>,
	<ijc+devicetree@...lion.org.uk>, <galak@...eaurora.org>,
	<linux@....linux.org.uk>, <linux-arm-kernel@...ts.infradead.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] ARM: dts: imx6dl: disable dma support for spi on
 i.mx6dl

On Mon, Sep 15, 2014 at 11:41:13AM +0200, Lucas Stach wrote:
> Am Mittwoch, den 10.09.2014, 13:30 +0800 schrieb Robin Gong:
> > There is one weird data in rxfifo after one full rx/tx transfer
> > done sometimes. It looks a design issue and hard to workaround
> > totally, so disable dma functhion here. And will re-enable it
> > once the root cause found.
> > 
> Sorry, I'm late to this as Shawn seems to already have picked up this
> patch, but this isn't the right way to fix the problem.
> 
> We made it clear at kernel summit last year that we try to not break
> existing DTs as booting a new kernel with an old DT is a valid use case.
> While you don't strictly violate this rule what you do here is only
> fixing systems booting with a new DT while leaving others broken.
> 
> If you are working around a hardware problem please disable DMA support
> in the driver. This will also allow you to enable it again, if you find
> another workaround without touching the DT again.

Okay, it's a valid point.  Patch dropped.

Shawn
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