[RISC-V][tech-os-a-see] Recommendation for identifying partition with firmware to be loaded from SD-card

[Aaron Durbin]

Hi,

On Mon, May 1, 2023 at 8:26 AM Heinrich Schuchardt <
heinrich.schuchardt at canonical.com> wrote:

> Linux distributions are interested in providing a single image which
> enables a high number of boards to boot. This is simple if the boot
> firmware (EDK II or U-Boot) is installed on flash.
>
> For boards that expect to load a boot loader like U-Boot from an SD-card
> it is necessary that the firmware locations for different boards
> on the SD-card don't collide.
>
> When loading from SD-card or eMMC the sector at which the binary
> starts has to be identified. The following has been implemented:
>
> - start from hard coded sector number
> - load file from FAT file system
> - load from given partition number
> - load from partition with boot flag set (MBR partioning only)
> - load from partition with specific type GUID
>
> Loading by partition type GUID seems the most appropriate to avoid
> collisions between the firmware for different boards.
>
> Often firmware is separated into multiple parts due to firmware
> restrictions, e.g. U-Boot SPL and main U-Boot (e.g. as .itb file).
>
> Here the same considerations apply. Using a partition type GUID to
> identify further firmware parts to be loaded is best suited to
> avoid collisions.
>
> I would suggest to add a recommendation to the EBBR specification
> to use SoC specific partition type GUIDs to identify firmware to
> be loaded from SD-card.
>

Who is loading the firmware that is identified by a GUID?  And how does
that tie into Linux distros? I don't see anything wrong w/ the
recommendation, but I didn't completely follow which piece of software is
loading firmware and how the GUID reduces the problems. Also, is this "SoC
specific partition type GUID" unique per SoC? Or is it expected to be a
global GUID?


>
> Please, provide your feedback.
>
> Best regards
>
> Heinrich
>
>
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