[PATCH v2 00/41] Initial implementation of standard boot

Heinrich Schuchardt xypron.glpk at gmx.de
Thu Oct 28 20:09:35 CEST 2021

On 10/28/21 7:59 PM, Tom Rini wrote:
> On Thu, Oct 28, 2021 at 06:50:02PM +0100, Peter Robinson wrote:
>> On Thu, Oct 28, 2021 at 6:47 PM Tom Rini <trini at konsulko.com> wrote:
>>> On Thu, Oct 28, 2021 at 06:37:42PM +0100, Peter Robinson wrote:
>>>> On Wed, Oct 27, 2021 at 3:11 PM Simon Glass <sjg at chromium.org> wrote:
>>>>> Hi Heinrich,
>>>>> On Wed, 27 Oct 2021 at 05:38, Heinrich Schuchardt
>>>>> <heinrich.schuchardt at canonical.com> wrote:
>>>>>> On 10/24/21 01:25, Simon Glass wrote:
>>>>>>> The bootflow feature provide a built-in way for U-Boot to automatically
>>>>>>> boot an Operating System without custom scripting and other customisation.
>>>>>>> This is called 'standard boot' since it provides a standard way for
>>>>>>> U-Boot to boot a distro, without scripting.
>>>>>>> It introduces the following concepts:
>>>>>>>      - bootdev - a device which can hold a distro
>>>>>>>      - bootmeth - a method to scan a bootdev to find bootflows (owned by
>>>>>>>                   U-Boot)
>>>>>>>      - bootflow - a description of how to boot (owned by the distro)
>>>>>> Please, describe why you are suggesting this change.
>>>>>> Replacing a script by a devicetree chunk is just decreasing flexibility
>>>>>> and increasing complexity. Where is the benefit?
>>>>>> I am missing a description here of where and how a boot flow shall be
>>>>>> defined. Describing some device-tree binding in patch 40/41 does not
>>>>>> replace describing the development and usage workflow. Who will provide
>>>>>> which bootflow information when?
>>>>>> You still have an open discussion with Linaro about the source of
>>>>>> devicetrees. This discussion needs to be finalized before considering
>>>>>> this series.
>>>>>> In my view bootflows cannot be defined in the devicetree because prior
>>>>>> firmware providing a devicetree is completely independent of any distro
>>>>>> and therefore cannot provide a distro specific bootflow.
>>>>> There is actually no need to use devicetree here. I think you might
>>>>> have the wrong end of the stick. It is certainly possible to add nodes
>>>>> to configure things, if needed, but it works find without any changes
>>>>> to the devicetree, as you can see from the rpi_3 patch.
>>>>> There are several aims with this effort:
>>>>> - Provide a standard way to boot anything on U-Boot, that everyone can
>>>>> plug into (distros, board vendors, people using a custom flow)
>>>> I as a distro maintainer don't want this, we already get the "standard
>>>> way to boot" from UEFI, this just feels like another unnecessary
>>>> abstraction to that.
>>> Right.  But part of the problem is "How do I find UEFI".  Something
>>> somewhere needs to be configurable to say where to look, yes?
>> Is this question from the board PoV, the developer of U-Boot or the
>> distro trying to boot?
>> If you mean from a boot flow PoV for UEFI to find the HW that contains
>> the OS to boot I thought that was handled elsewhere in the series.
> What I mean is that today looking at Pi we have:
> #define BOOT_TARGET_DEVICES(func) \
>          BOOT_TARGET_MMC(func) \
>          BOOT_TARGET_USB(func) \
>          BOOT_TARGET_PXE(func) \
>          BOOT_TARGET_DHCP(func)
> As the board maintainer set that as the list of places to start looking
> for the next payload (say the GRUB EFI binary).  Simon's series replaces
> that with I think he said "bootflow scan -b".  And then the above env
> portion is replaced with, well, what's documented in patch #40 if you
> don't just want to rely on device probe order.
> Because we need to have _something_ that says where to look for what,
> yes?  Or should that be replaced entirely with efi vars and
> BootOrder/BootXXX and "bootefi bootmgr $fdt_addr_r" ?

UEFI variables must be supported for booting via UEFI. But if no valid
image can be found via the UEFI variables you have to scan the EFI
system partition for the file EFI/BOOT/BOOT<arch>.EFI and run it. This
requires to scan all block devices for the ESP.

Furthermore not all distributions use UEFI by default on all systems.

Best regards


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