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

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Message-ID: <20140917085106.GB6369@Robin-OptiPlex-780>
Date:	Wed, 17 Sep 2014 16:51:08 +0800
From:	Robin Gong <b38343@...escale.com>
To:	Alexander Holler <holler@...oftware.de>
CC:	<shawn.guo@...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>,
	<fugang.duan@...escale.com>
Subject: Re: [PATCH v2] ARM: dts: imx6dl: disable dma support for spi on
 i.mx6dl

On Tue, Sep 16, 2014 at 11:41:55AM +0200, Alexander Holler wrote:
> Am 16.09.2014 05:52, schrieb Robin Gong:
> >On Mon, Sep 15, 2014 at 01:50:02PM +0200, Alexander Holler wrote:
> >>Am 10.09.2014 07:30, 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.
> >>
> >>Hmm, I experience problems with DMA too but on uart3. I'm using the same
> >>workaround for the uart (I've just commented out the dma entries in the DT).
> >>The problem manifests itself here such, that brcm_patchram_plus
> >>hangs while uploading the firmware to a BCM4330 connected at uart3
> >>(reproducible).
> >>
> >>So maybe there is a bug in the DMA-engine which not only effects
> >>SPI. Or both drivers contain the same error in handling DMA (maybe
> >>through c&p).
> >>But that's just specualtion from me, I haven't looked further into
> >>that problem.
> >>
> >>Regards,
> >>
> >>Alexander Holler
> >Thanks for your information share. But my issue should be caused by hardware,
> >since everything is ok if it runs on other i.mx6 chip. Is your board also based
> >on i.mx6 chip? If yes, hope you can raise your issue in freescale community or
> >contact with Andy whose mail address added in CC list fugang.duan@...escale.cm.
> >We have fix some bugs in UART DMA case.
> 
> It's an i.mx6q (Wandboard quad c1) where I have this problem with
> mainline and much older (but heavily patched freescale 3.10.x based)
> kernels. A quick web-search suggests that this problem exists since
> a long time (noticed mainly by people which try to use BT as this
> seems to be the major use case for high speed serial communication).
> 
> Regards,
> 
> Alexander Holler
Yes, we just have fixed the BT issue over high speed UART last month. Suggest
you trying our patches based on v3.10.
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