Re: SDIO "SD2" vs. SD-card "SD3" interface on BayTrail

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Tue, 2017-07-04 at 16:12 +0200, Stefan Roese wrote:
> 
> On 04.07.2017 15:53, Andy Shevchenko wrote:
> > On Tue, 2017-07-04 at 14:53 +0200, Stefan Roese wrote:
> > > Hi,
> > > 
> > > we are currently investigating, if its possible to connect a SDIO
> > > device (WLAN module) to the SD-card interface "SD3" of the
> > > BayTrail
> > > SoC instead of the SDIO interface "SD2". The BayTrail manual
> > > states,
> > > that the SDIO interface is capable of connecting SDIO devices. Is
> > > this also possible for the SD-card interface "SD3", even if its
> > > not
> > > explicitly mentioned in the manual? If not, why is this not
> > > possible?
> > > 
> > > Any insight on this would be really helpful.
> > 
> > Hmm... I have no documentation for SD/SDIO/eMMC for BayTrail except
> > the
> > public one. Internally I found some charts that shows similarities
> > between two. So, taking that into consideration I would suggest to
> > try
> > it out on real hardware (MinnowBoard MAX, for example), only
> > impediment
> > I can see is the absence of support in the drivers in Linux OS. If
> > you
> > need it only in U-Boot, you perhaps may fix it easily.
> 
> Its not only for U-Boot unfortunately. Do you think, a quick test in 
> Linux should be possible by simply swapping the PCI device IDs in
> sdhci-pci.core.c (PCI_DEVICE_ID_INTEL_BYT_SDIO vs.
> PCI_DEVICE_ID_INTEL_BYT_SD)?

If it utilizes ACPI (card detection) I'm not sure you can magically get
it working, though it worth to try.

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy