Problems after recent changes to meson-gx-mmc driver

[hkallweit1@gmail.com (Heiner Kallweit)]

Am 10.09.2017 um 17:08 schrieb Jerome Brunet:
> On Sat, 2017-09-09 at 22:20 +0200, Heiner Kallweit wrote:
>> I checked further and setting the tx clock phase back to 0 fixes the issue for
>> me.
>> ("mmc: meson-gx: change default tx phase" changes it from 0 to 270.)
>> But as you write 0 seems to break certain other systems.
> 
> That was my second guess ...
> 
> As I mentioned in the commit message, 270 is working fine for the setups I have
> tested but I always wondered if that would be the case for every possible
> setups/boards/modes.
> 
> Would you mind testing 90 and 180 as well with your setup ? I'll make another
> pass on the different setups I have access to. Please stick to hs200 and drop
> hs400 for this test. I'm still unsure if doubling the clock after doing the
> tuning may affect the phase tuning ... lets keep that out of the way for now.
> 
I tested the other tx clock settings with HS200/200MHz.

0: No errors
90: 6 CRC errors, otherwise system works normal.
180: Lots of CRC errors, but system still works.
270: So many errors that root file system gets corrupted and is mounted r/o.

Seems like we won't find a tx clock phase working on all systems.
So maybe the tuning needs to be extended to check all tx / rx clock
phase combinations.

IIRC I went with a fixed tx clock phase because other combinations of
tx / rx clock phase selected by an experimental tuning algorithm
worked fine when tuning but produced errors later.