On 7/12/21 5:15 PM, 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.dowle@4rf.com wrote:
I submitted an almost identical patch. See https://github.com/u-boot/u-boot/commit/eb39d8ba5f0d1468b01b89a2a464d18612d3...
This patch eventually had to be reverted (https://github.com/u-boot/u-boot/commit/5675ed7cb645f5ec13958726992daeeed16f...), 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 simplyhangs. 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.
If I recall this correctly, DT node alignment is 4 byte and that is what DTC emits. If you have fitImage with embedded data, you basically end up with
/ { prop1 = "string1"; prop2 = "string2"; };
where the "string2" is aligned to 4 bytes. And that is what U-Boot expects when it tries to access those data in-place in SPL.
The problem with the reverted patch was that it made U-Boot assume the alignment is 8 bytes, and that actually works only if you use fitImage with external data (mkimage -E), but with embedded data (mkimage default) not so much. That caused off-by-4 error in some cases and that made the SPL hang.
Note, as I indicated in this patch, now with libfdt 1.6.1, the alignment to 8 byte is a must-have. So we have to do such alignment anyway.
@Tom may fill in why libfdt commit commit 5e735860c478 ("libfdt: Check for 8-byte address alignment in fdt_ro_probe_()") was made to have the 8-byte alignment requirement.
Note that it's not so much since libfdt 1.6.1 but that since always the device tree has required 8 byte alignment.
DT alignment was always 4 byte , no ?
It's just that on 32bit platforms 4-but-not-8 byte alignment tends to not be fatal but on 64bit platforms it is.
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