[U-Boot] [PATCH v4] mmc: socfpga_dw_mmc: Enable calibration for drvsel and smplsel

[Chin Liang See]

On Wed, 2015-12-02 at 15:39 +0100, Marek Vasut wrote:
> On Wednesday, December 02, 2015 at 06:52:17 AM, Chin Liang See wrote:
> 
> [...]
> 
> > > OK, this is bad. Originally, if we didn't specify these in the
> > > DT, we
> > > would
> > > use the default values of 0x3 and 0x0 , but now we do the
> > > calibration. I wonder,
> > > do we care about DT ABI compatibility on the U-Boot level or not
> > > ?
> > 
> > If the compatibility failed, it will still invoke the calibration
> > to
> > get the correct value. Just that its in the cost of boot time.
> 
> Hopefully the calibration does it's job then.
> 
> > At same time, I am rethinking another email thread on suggesting to
> > put
> > this into common dw_mmc code. Here are my proposal
> 
> Having this in common code would make sense.
> 
> > 1. Put back the correct default value for DT ABI compatiblity
> > 2. Adding a node to enable calibration. If node not exist,
> > calibration
> > will disabled as default.
> 
> But "enable calibration" is not really a hardware property, so it
> shouldn't
> be in the DT. The DT is purely a hardware description and only the
> smplsel
> and drvsel fit into this, some "enable-calibration" does not.
> 

Sound reasonable. In this case, I can put this into KConfig where user
can configure this easily through menuconfig. 

Thanks
Chin Liang


> > 3. Some common calibration algo will go into dw_mmc.c
> > 4. platform specific such as on configuring the clksel and smplsel
> > will
> > be part of platform specific dw_mmc file such as socfpga_dw_mmc.c
> 
> OK
> 
> > This hope will work for both everyone especially for socfpga and
> > exynos
> > platform. Any thoughts?
> > 
> > Thanks
> > Chin Liang
> 
> Best regards,
> Marek Vasut