On 7/13/21 3:47 PM, Tom Rini wrote:
On Mon, Jul 12, 2021 at 11:01:24AM -0500, Alex G. wrote:
On 7/12/21 10:15 AM, Tom Rini wrote:
On Mon, Jul 12, 2021 at 01:36:14PM +0800, Bin Meng wrote:
On Mon, Jul 12, 2021 at 1:21 PM Reuben Dowle <reuben.do...@4rf.com> wrote:
I submitted an almost identical patch. See
https://github.com/u-boot/u-boot/commit/eb39d8ba5f0d1468b01b89a2a464d18612d3ea76
This patch eventually had to be reverted
(https://github.com/u-boot/u-boot/commit/5675ed7cb645f5ec13958726992daeeed16fd114),
because it was causing issues on some platforms that had FIT on 32 bit
boundary. However I continue to use it in production code, as without it the
boot on my platform aborts.
I don't have time to investigate why this was happening, but you need to check
this code won't just cause exactly the same faults.
Thanks for your information.
+Marek who did the revert
The revert commit message says:
"The commit breaks booting of fitImage by SPL, the system simply
hangs. This is because on arm32, the fitImage and all of its content
can be aligned to 4 bytes and U-Boot expects just that."
I don't understand this. If an address is aligned to 8, it is already
aligned to 4, so how did this commit make the system hang on arm32?
I think this had something to do with embedding contents somewhere in
the image? There is a thread on the ML from then but I don't know how
informative it will end up being.
It's true that the flat devicetree spec requires an 8-byte alignment, even
on 32-bit. The issues here are specific to u-boot.
SPL and u-boot have to agree where u-boot's FDT is located. We'll look at
two cases:
1) u-boot as a FIT (binary and FDT separately loaded)
2) u-boot with embedded FDT
In case (1) SPL must place the FDT at a location where u-boot will find it.
The current logic is
SPL: fdt = ALIGN_4(u_boot + u_boot_size)
u-boot: fdt = ALIGN_4(u_boot + u_boot_size)
In case (2), SPL's view of the FDT is not relevant, but instead the build
system must place the FDT correctly:
build: fdt >> u-boot.bin
u-boot: fdt = ALIGN_4(u_boot + u_boot_size)
We have 3 places that must agree. A correct and complete patch could change
all three, but one has to consider compatibility issues when crossing u-boot
and SPL versions.
I had proposed in the revert discussion that SPL use r2 or similar mechanism
to pass the location of the FDT to u-boot.
I'm not sure that we need to worry too much about mix-and-match
SPL/U-Boot, but documenting what to go change if you must do it
somewhere under doc/ would be good. I think we can just switch to
ALIGN(8) not ALIGN(4) and be done with it?
Remember, there is also falcon boot. And we definitely have to be able
to have old u-boot (SPL) boot new fitImage and vice versa.
