[U-Boot] [U-Boot,RFC] efi: variable support

[Heinrich Schuchardt]

On 06/26/2017 12:13 AM, Rob Clark wrote:
>>> (the whole idea of a single static dtb for a SoC is nice in theory
>>> until you realize that complex SoC's like snapdragon are still pushing
>>> the boundaries of what we have figured out how to model in dt)
>>>
>>> BR,
>>> -R
>>>
>> Have a look at Debian/Ubuntu package flash-kernel.
>>
>> After installing a new kernel update-initramfs triggers flash-kernel.
>> flash-kernel looks up the value provided by file
>> /proc/device-tree/model
>> in a database file to find the correct dtb and installs it in /boot. It
>> further sets a symbolic link
>> /boot/dtb
>> to the dtb. So u-boot can simply load /boot/dtb and pass it to grub.
> but this doesn't work if you want to be able to (for example) unplug a
> disk from device A and plug it in to device B, does it?
> 
>> If static dtbs are not enough for your requirements look at device
>> overlay trees.
> I do have some interest in overlays, mostly because currently the
> firmware generates psuedo-random eth/wifi/bt MAC addrs based on some
> board specific info (like emmc part serial #, for example).. which we
> currently loose out from if not using the qcom specific lk->kernel
> boot chain.  But I guess that is a bit of a different topic.
> 
> BR,
> -R
> 

U-Boot can load device tree overlays. Here is what worked for me:

=> load mmc 0:1 0x01000000 dtb
29830 bytes read in 14 ms (2 MiB/s)
=> fdt addr 0x01000000 0x80000
=> load mmc 0:1 0x01080000 rtc.dtbo
529 bytes read in 8 ms (64.5 KiB/s)
=> fdt apply 0x01080000
=> load mmc 0:4 0x13000000 efi/debian/grubaa64.efi
reading efi/debian/grubaa64.efi
120832 bytes read in 7 ms (16.5 MiB/s)
=> bootefi 0x13000000 0x01000000

U-Boot must be configured with
CONFIG_OF_LIBFDT_OVERLAY
to support device tree overlays.

Best regards

Heinrich Schuchardt