Re: [PATCH] i2c: mxs: Rework the PIO mode operation

[Lucas Stach <l.stach-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]

Hi Marek,

Am Montag, den 15.07.2013, 04:05 +0200 schrieb Marek Vasut:
> Hi,
> 
> > Analyze and rework the PIO mode operation. The PIO mode operation
> > was unreliable on MX28, by analyzing the bus with LA, the checks
> > for when data were available or were to be sent were wrong.
> > 
> > The PIO WRITE has to be completely reworked as it multiple problems.
> > The MX23 datasheet helped here, see comments in the code for details.
> > The problems boil down to:
> > - RUN bit in CTRL0 must be set after DATA register was written
> > - The PIO transfer must be 4 bytes long tops, otherwise use
> >   clock stretching.
> > Both of these fixes are implemented.
> > 
> > The PIO READ operation can only be done for up to four bytes as
> > we are unable to read out the data from the DATA register fast
> > enough.
> > 
> > This patch also tries to document the investigation within the
> > code.
> > 
> > Signed-off-by: Marek Vasut <marex-ynQEQJNshbs@public.gmane.org>
> > Cc: Alexandre Belloni <alexandre.belloni-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
> > Cc: Fabio Estevam <r49496-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
> > Cc: Lucas Stach <l.stach-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
> > Cc: Shawn Guo <shawn.guo-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> > Cc: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
> > Cc: <to-fleischer-zqRNUXuvxA0b1SvskN2V4Q@public.gmane.org>
> 
> I so far got confirmation from ALexandre this patch works. Can someone else test 
> it please? I'd like to roll out a final version to close this issue.
> 
Sorry, I wasn't able to test it until now. I now have the respective
hardware at my desk again, so I'll get you a report by latest day after
tomorrow.

I'll post some comments to the patch itself in the meantime.

> One question remain though -- shall we have the PIO as an experimental feature 
> and disable it by default OR not ?
> 
> Thanks!
> 
> Best regards,
> Marek Vasut

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