Hi Mark,
On Wed, 6 Dec 2023 at 13:00, Mark Kettenis mark.kettenis@xs4all.nl wrote:
From: Ilias Apalodimas ilias.apalodimas@linaro.org Date: Wed, 6 Dec 2023 12:31:15 +0200
Hi Caleb,
Late to the party, but I'll respond to as much as I can
On Tue, 21 Nov 2023 at 19:09, Caleb Connolly caleb.connolly@linaro.org wrote:
Historically, Qualcomm boards in U-Boot have all had their own board/qualcomm/xyz directory, their own CONFIG_TARGET_XYZ option, their own hardcoded sysmap-xyz.c file, and their own U-Boot specific devicetree with little/no compatibility with upstream DT.
This series makes a few final prepatory changes, and then replaces almost all of the board specific code with generic alternatives. The end result is that all Qualcomm boards both current and future (with the exception of the db410c and db820c) can be supported by a single U-Boot binary by just providing the correct DT. New boards can be added without introducing any addition mach/ or board/ code or config options.
Due to the nature of this change, the patch ("mach-snapdragon: generalise board support") has become pretty big, I tried a few different ways to represent this in git history, but the other methods (e.g. adding a stub "generic" target and removing it again) were more confusing and made for much messier git history. The current patch is mostly atomic, but requires regenerating the config.
The QCS404 EVB board had some code to enable the USB VBUS regulator, this is dropped in favour of a adding a new vbus-supply property to the dwc3-generic driver. This will also be used by the dragonboard845c in a future patch. This handles the common case of a board requiring some regulator be enabled for USB host mode.
A more detailed description of the changes is below.
== Memory map ==
The memory map was historically hardcoded into U-Boot, this meant that U-Boot had to be built for a specific variant of a device. This is changed to instead read the memory map from the DT /memory node.
Additionally, most boards mapped addresss 0x0 as valid, as a result if a null pointer access happens then it will cause a bus stall (and board hang). This is fixed so that null pointer accesses will now correctly throw an exception.
== DT loading ==
Previously, boards used the FDT blob embedded into U-Boot (via OF_SEPARATE). However, most Qualcomm boards run U-Boot as a secondary bootloader, so we can instead rely on the first-stage bootloader to populate some useful FDT properties for us (notably the /memory node and KASLR seed)
Note that the kaslr-seed is not so useful when booting with EFI. The kernel's EFI-stub ignores that and instead tries to randomize the physical placement of the kernel if it finds an EFI_RNG protocol.
OpenBSD will use it though. And other OSes might as well.
Yea, I remember that, but efi_try_purge_kaslr_seed() purges it anyway if there's an EFI_RNG protocol installed. U-Boot also has other ways of injecting it. Perhaps we could keep it and combine rng-seeds in the future I guess.
Thanks /Ilias
and fetch the DTB that it provides. Combined with the memory map changes above, this let's us entirely avoid configuring the memory map explicitly.