[U-Boot] [PATCH v2 1/2] arm: socfpga: mmc: Enable calibration for drvsel and smpsel

[Chin Liang See]

Hi,

On Fri, 2015-08-21 at 05:03 +0200, marex at denx.de wrote:
> On Friday, August 21, 2015 at 03:25:00 AM, Chin Liang See wrote:
> > On Fri, 2015-08-21 at 03:07 +0200, marex at denx.de wrote:
> > > On Friday, August 21, 2015 at 02:54:00 AM, Chin Liang See wrote:
> > > > Hi guys,
> > > 
> > > Hi,
> 
> Hi,
> 
> > > > Any comment or ack for this patch?
> > > 
> > > Please don't expect that the reviewers/maintainers have nothing else on
> > > their plate but to review your patch. Besides, this change is really low
> > > priority one, since thus far the SD/MMC works fine on all of the SoCFPGA
> > > boards to my knowledge.
> > > 
> > > Also, I thought we agreed to wait for Simon to comment on this patch.
> > > You don't have to repost a patch before the discussion settles a bit.
> > > This doesn't help, it only puts burden on the receiving side, chill :)
> > > Let alone the fact that this code should be part of the DWMMC core, as
> > > it is not socfpga specific.
> > > 
> > > What I would be really interested in is a proper description of the
> > > calibration algorithm. What is the goal and how do you achieve it ?
> > 
> > Actually I am probing the efforts needed for this patch before moving to
> > next one. While for the SDMMC calibration, it is not needed if the SD
> > card is routed near to the chip. We have incident where SD access failed
> > as they routed few inches away.
> 
> Does the calibration really help or is that a problem with the board ?
> It'd be nice if you put effort into this patch to get it done correctly :)

It's related to the board. When the trace route is not properly design,
it might failed when communication between the controller and card at
high speed. The calibration will ensure the correct data being driven
and sampled at correct window. As this seems applicable for dwmmc, let
me take a look into other vendor implementation. Thanks again for the
advise :)

Chin Liang

> 
> > With that, let wait for Simon and I shall move on next item.
> 
> If you're waiting for Simon, it might be a good idea to actually CC him :-)
> 
> Best regards,
> Marek Vasut