mmc: core: complete/wait_for_completion performance

[Jörg Krause]

Hi Stefan,

On Wed, 2016-12-14 at 19:57 +0100, Stefan Wahren wrote:
> Hi Jörg,
> 

[snip]

> > > 
> > > did you try cyclictest [1]?
> > 
> > Not yet. Not sure what to measure and which values to compare here.
> 
> i tought you have the vendor kernel and the mainline kernel available
> for your platform.
> 
> So you could compare the both kernels.

Yes, that's right. I will have a look at this tool.

> > 
> > > 
> > > Beside the time for a request the amount of requests for the
> > > complete
> > > iperf test
> > > would we interesting. Maybe there are retries.
> > > 
> > > I'm still interested in your PIO mode patches for mxs-mmc even
> > > without clean up.
> > 
> > Actually, the patch does not implement a PIO mode, but drops DMA
> > and
> > uses polling instead. I've attached the patch.
> 
> Thanks. I applied it, but unfortunately this breaks SD card support
> for my Duckbill and the kernel isn't able to mount the rootfs:
> 
> [    2.267073] mxs-mmc 80010000.ssp: initialized
> [    2.272624] mxs-mmc 80010000.ssp: AC command error 0xffffff92

Sorry, I messed up the branches. I attached the correct patch which is
working for me on Linux v4.9.

Jörg
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