[U-Boot] U-Boot on Minnowboard Max

[Bin Meng]

Hi,

+Simon, ML and Stefan.

On Wed, Jun 8, 2016 at 11:58 PM, vinoth eswaran <evinoth1206 at gmail.com> wrote:
> Hello Bin,
>
>   Sorry that I don't know how not to reply without top-posting. I
> don't know which settings to change, google didn't help me in this
> case.
>

It's a posting style. See https://en.wikipedia.org/wiki/Posting_style.
We use bottom-posting.

> I have tested your patch on my target and found out that now mounting
> root file system by sd card is fine. Thanks a lot :)
>

Great!

> Now I am seeing another issue , the USB3.0 port (bottom) is not
> working. I am sure that both ports are working fine with UEFI
> Firmware. I tested by connecting a mouse to the USB port , in the
> USB2.0 port (upper) it is working fine but in the USB3.0 port the
> mouse is not getting detected. I am not sure why it is happening. I
> looked into the kernel logs but I didn't get any error/debug messages.
> Can you please check this on your board also.
>

Do you mean xHCI is not working under U-Boot? xHCI is not enabled in
U-Boot yet. IIRC, U-Boot's xHCI driver does not support Intel
controller yet.

> Do you have any documents regarding the u-boot to kernel handover,
> what all informations does u-boot  handover to Linux Kernel. It would
> be great help.

This is documented in kernel doc:
https://www.kernel.org/doc/Documentation/x86/boot.txt

> I thought that the MMC driver issue is on Linux Kernel side, but it
> was some offset and probing issue in the u-boot.
>

Umm, it's hard to tell. Starting from BayTrail, Intel's SoC is more
and more like an ARM SoC, with many GPIOs and pinmux that needs to be
configured. Linux kernel does provide driver for the BayTrail pinctrl,
but so far no mainline driver is making use of it. The generic x86
kernel image is not aware of any board-specific I/O configuration so
some peripherals (like in this case the SD controller) won't work out
of the box. The mainline Linux kernel expects the underlying
bootloader to do the I/O configuration, IOW, kernerl is not bootloader
agnostic yet on x86. It relies on whatever bootloader (UEFI BIOS,
coreboot, U-Boot) to do such kind of work.

Regards,
Bin