On Wed, 5 Jun 2024 at 18:12, Caleb Connolly caleb.connolly@linaro.org wrote:
Hi Sumit,
On 05/06/2024 07:31, Sumit Garg wrote:
Hi Caleb,
On Mon, 3 Jun 2024 at 18:19, Caleb Connolly caleb.connolly@linaro.org wrote:
Hook up support for capsule updates loaded from disk on Qualcomm platforms.
Most Qualcomm devices have an A/B partition layout, with most partitions duplicated. The metadata on which slot is active is stored in the GPT headers in the vendor-specific attribute bits of each partition.
It's good to see capsule updates support coming up for Qualcomm platforms. AFAICS, with this series we only update U-Boot on the current active partition. IOW, real A/B support is still not supported. Do you think it is possible for U-Boot to update metadata in GPT headers and for proprietary bootloaders to pick up the U-Boot from the updated partition?
Yes this would be possible, I have some WIP patches to let us modify the slot attribute bits and write back the header.
Nice to hear that possibility.
The reason I haven't implement A/B is because we don't support it from the OS level on any of the boards I work on. We often patch ABL to disable or skip the slot logic and flash a partition table without slots. It also unlocks a bunch of additional complexity...
Please have a look at an alternative FWU Multi Bank Updates [1]. AFAIK, the UEFI capsules updates feature from the OS point of view remains transparent. It's more about how those capsules are interpreted with the logic to update the inactive partition and metadata such that subsequent boot uses the updated firmware.
[1] https://docs.u-boot.org/en/latest/develop/uefi/fwu_updates.html
This isn't super high on my todo list but I'd be happy to help if someone wants to enable this functionality. We'd need:
- Upstream support for modifying the GPT (see my PoC at [1] and [2]).
- Logic to configure flashing the active or inactive slot
This logic would have to run after the capsule update, I don't know if there is currently a way to add a callback after the update.
If we enable updating other images (like XBL, hyp, tz, etc), we would need to either agree that a capsule update would have to update ALL partitions, or implement logic to copy over partitions that weren't flashed to the other slot.
I would be interested to see how we can plug Qcom specific pieces underneath in order to have multi bank updates. However, this patchset is still usable in its current form. We can later add the real A/B functionality.
Apart from patch #4 where we are still discussing the finer details, feel free to add:
Acked-by: Sumit Garg sumit.garg@linaro.org
-Sumit