Subject: Re: [PATCH 2/2] ARM: dts: imx7: add DMA properties for ECSPI

From: Trent Piepho <[email-masked]>
Date: Wed, 13 Feb 2019 00:07:17 +0000

On Tue, 2019-02-12 at 17:37 -0200, Fabio Estevam wrote:
> On Mon, Feb 11, 2019 at 8:22 PM Trent Piepho <[email-masked]>
> wrote:
> 
> > > Just trying to understand if the SDMA firmware plays a role on
> > > this
> > > behavior or not.
> > 
> > The ROM firmware only.
> 
> Does the problem also happen if the external SDMA firmware is used?
> Just trying to narrow it down.

Tried SDMA firmware 4.2.  Still broken.  No apparent change.

Get 4 cycle pause after each byte.

And crash while/after using DMA.  Clearly some sort of memory
corruption going on.  Fortunately, it's very reliable that using DMA
almost immediately causes a problem and this is easy to reproduce.  I
think that indicates it's either clobbers a lot of RAM, or consistently
manages to hit a very important location for kernel memory allocators.

I've got an idea of where that might be happening that I'm looking
into.

I think it's reasonable to add the dma attributes, but put a check in
the spi-imx driver to disable DMA on imx7d at least.
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