[U-Boot] [PATCH 06/11] tegra20: switch over seaboard and ventana to use tablebased pinmux

[Lucas Stach]

Hello Simon,

Am Samstag, den 26.01.2013, 10:20 +1300 schrieb Simon Glass:
> Hi Lucas,
> 
> On Fri, Jan 25, 2013 at 7:22 AM, Lucas Stach <dev at lynxeye.de> wrote:
> > Am Freitag, den 25.01.2013, 06:54 +1300 schrieb Simon Glass:
> >> Hi Lucas,
> >>
> >> On Fri, Jan 25, 2013 at 5:48 AM, Lucas Stach <dev at lynxeye.de> wrote:
> >> > Init pinmux in one shot, in order to avoid any conflicts.
> >> >
> >> > Signed-off-by: Lucas Stach <dev at lynxeye.de>
> >> > ---
> >> >  board/nvidia/seaboard/seaboard.c | 133 +++++++++++++++++++++++++++++++++------
> >> >  include/configs/seaboard.h       |   3 +
> >> >  include/configs/ventana.h        |   3 +
> >> >  3 files changed, 121 insertions(+), 18 deletions(-)
> >>
> >> This seems like a lot of code and presumably quite a bit of
> >> duplication between boards. What sort of conflicts does this avoid,
> >> and is it the only way of avoiding them?
> >>
> > I don't see it as duplication, but as explicitly spelling out how the
> > pinmux configuration should be set up on a certain board.
> 
> I mean that the table is very similar for different boards, so looks
> like duplicated coded (133 very similar lines for each board).
> 
> Also, this seems to break FDT use. At present it is possible (I think)
> to boot the same U-Boot on any board, with the device tree specifying
> the config. With your change that is no longer possible, I think?
> 
> Looking ahead to T114 I see a similar problem. The funcmux approach
> was a compromise in that we could just select appropriate values for
> each function - there was no agreement on how to put this in the FDT
> though (my intention was that it would depend on the kernel binding,
> but that is now defined, so what excuse do we have for not
> implementing it in U-Boot?).
> 
That Tegra30 doesn't do so either. ;) But I agree, that's no valid
excuse and we should resolve this before Tegra114 introduces more of
this stuff. See below. 
> >
> > Before this change we would leave some pads uninitialised in their
> > (random) reset configuration. For example on the Colibri this leads to
> > NAND not working as it's wired up to the KBC pads. If we only configure
> > those, ATC will remain in it's reset state and would be also configured
> > to the NAND function, which leads to fail. Having an explicit, known to
> > be conflict free configuration for all pads avoids all those unpleasant
> > surprises.
> 
> Well yes, but we seem to be right back to where we started, with the
> FDT unable to describe a key feature of the boards (pinmux).
> 
I see your point now. The obvious answer for now is: it's not regressing
functionality, as we were never able to boot the same U-Boot image by
just changing the DT.

But yes in the end we want to pack this information into the DT files.
But even then it would be nice if people would test this pachset, as I
imagine DT based pinmux is the same as tablebased pinmux, just in a
slightly different flavour. ;) So if people test the tablebased config
now, we can do the conversion to DT based with a lot more confidence.

I'll look into using the kernel pinmux binding minus the MUX stuff, as I
think there's no real reason to have this in U-Boot.

Regards,
Lucas