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

[Michal Suchanek]

On 4 March 2015 at 16:17, Siarhei Siamashka <siarhei.siamashka at gmail.com> wrote:
> 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).

For things selectable from a menu it might be possible to use the
volume and power keys as the Android recovery does.

Driver for the power key is already in u-boot. It's just not hooked up
to provide input.

>
> 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.

I pretty much use only the OTG port when I boot GNU/Linux on a tablet.
yes, I can get display output but any input has to  come over OTG so I
use ethernet gadget and ssh.

That also happens to cover downloading stuff in case the WiFi chipset
is not supported. I have yet to see an Allwinner tablet with supported
touchscreen.

Thanks

Michal