[U-Boot] [PATCH] sunxi: Machine id hack to prevent loading buggy sunxi-3.4 kernels

[Siarhei Siamashka]

On Tue, 03 Mar 2015 08:17:56 +0000
Ian Campbell <ijc+uboot at hellion.org.uk> wrote:

> On Mon, 2015-03-02 at 00:07 +0200, Siarhei Siamashka wrote:
> > Just one suggestion. It would be really nice if the Debian installer
> > could present itself on all the available consoles, so that the user
> > can use any of them for providing input to the installer.
> 
> There is some reason why d-i doesn't do this by default. I think it's to
> do with bricking or otherwise interfering with devices attached to
> serial ports e.g I think Braille terminals were mentioned, but I suppose
> any random device might not like getting random strings of characters.

There could be perhaps a fake kernel cmdline option to specify the
exact list of consoles to be used by the Debian installer?

> > Otherwise there will be a need to provide separate SD card images for
> > the HDMI console (for the Raspberry Pi wannable competitors), the UART
> > serial console (A10/A20 development boards without HDMI) and the USB OTG
> > serial gadget console (for the tablets without HDMI). Instead of just
> > having only a single SD card image to handle everything automatically.
> 
> I've backported DT the /chosen/stdout-path support to the kernel a while
> ago and I thought together with Hans' u-boot patches to populate this
> field with the right thing then console selection would Just Work(tm).

I need to check this new feature myself, especially whether it can do
user input handling.

> At least for HDMI vs. UART since I'm not quite sure how the OTG gadget
> console is presented to Linux and whether it falls into this stuff
> correctly.

It should be seen as just one more /dev/tty* entry (maybe USB or ACM).

My original plan from

    http://lists.denx.de/pipermail/u-boot/2015-January/202306.html

was to make the bootable SD card just drop into the FEL mode in the
case if an A13/A23 SoC is detected or if there is no HDMI monitor
connected. Then a custom application running on a desktop PC could
upload a custom SPL for the only purpose of identifying the DRAM size
and bus width. Then present a choice of the possibly matching devices
to the user, boot the system via FEL, run hardware reliability tests
and move on to preparing the rootfs.

But with the Debian installer, this becomes somewhat more difficult.
Because we need a way of handling user input during the installation
(for the language selection, time zone, and other things).

However with the new USB OTG code from Hans hopefully coming into the
Linux kernel, we can have everything much easier and more unified :-)
Basically, the serial port over USB should work fine even in Windows
(at least it works for the Arduino people):

    http://arduino.cc/en/Guide/Windows

And because the BROM is able to use USB OTG for the FEL mode on all
sunxi devices, the serial console over USB should also work in a
generic image without any special device dependent configuration.

> > Oh, and one more suggestion. The SD card partitioning could be also
> > improved in order to make it more user friendly. Right now the user may
> > be confused by the Debian installer regarding what to do with the
> > existing partition on the SD card (yes, it can be safely erased since
> > the installer is running from RAM and does not rely on the data from
> > that partition anymore).
> 
> I leave this one to Karsten who looks after the SD card images.

I just mean that the Debian installer could be a little bit more aware
of the target platform and guide the user appropriately without leading
to any surprises.

-- 
Best regards,
Siarhei Siamashka