Re: [PATCH] i.MX SPI DMA cleanup

[Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>]

On Wed, Feb 17, 2016 at 03:10:44PM +0100, Dirk Behme wrote:
> On 17.02.2016 14:54, Sascha Hauer wrote:
> >Hi Dirk,
> >
> >On Wed, Feb 17, 2016 at 02:42:33PM +0100, Dirk Behme wrote:
> >>Hi Sascha,
> >>
> >>On 17.02.2016 14:28, Sascha Hauer wrote:
> >>>This picks up a series sent by Anton Bondarenko last year. It
> >>>contains the remaining not yet upstreamed patches from Antons series
> >>>plus some more DMA related cleanup patches.
> >>>
> >>>My mission was to hunt a bug in the DMA code path sometimes causing
> >>>an additional word in the RX FIFO which locked up the driver in the
> >>>next transfer. It turned out that this was no bug in the driver but
> >>>instead in the device tree: We used the wrong SDMA script for i.MX6.
> >>>The ECSPI cores are connected through the SPBA, so according to the
> >>>reference manual we need the shp/mcu scripts rather than the app/mcu
> >>>scripts.
> >>
> >>
> >>Are you talking about what is known as "TKT238285 hardware issue"
> >>
> >>https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/spi/spi-imx.c?id=a02bb401f8ae264be782ee57d98bdd99f14c8022
> >
> >I am aware of this issue, but I have no idea if this is the same or
> >another issue. It says:
> >
> >>For TKT238285 hardware issue which may cause txfifo store data twice can only
> >>be caught on i.mx6dl, we use pio mode instead of DMA mode on i.mx6dl.
> >
> >What I saw here is that there was one word more than expected in the RX
> >FIFO. Since both RX and TX FIFO act synchronously it could be that the
> >additional word in the RX FIFO was caused by an additional word in the
> >TX FIFO as described above.
> 
> 
> The question behind all this is if we could drop
> 
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/spi/spi-imx.c?id=a02bb401f8ae264be782ee57d98bdd99f14c8022
> 
> ?

It seems on the i.MX6DL we (additionally) have another issue. I just
tested here on a i.MX6DL board with a NOR Flash connected. I saw the
same issue as I saw on the i.MX6Q, but on the i.MX6DL it cannot be fixed
by using the shp/mcu SDMA scripts.
Funny enough on the i.MX6DL the RXFIFO issue happens much more
frequently than on the i.MX6Q.

Sascha

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