On 19.10.18 08:33, AKASHI Takahiro wrote:
On Thu, Oct 18, 2018 at 09:25:04AM +0200, Alexander Graf wrote:
On 18.10.18 00:25, Tuomas Tynkkynen wrote:
Hi Alexander,
On Tue, 16 Oct 2018 15:04:26 +0200 Alexander Graf agraf@suse.de wrote:
...
Glancing at cmd/pxe.c, there is a problem though, in that if ${fdt_addr_r} were defined, a PXE file using the FDTDIR directive would attempt loading a dtb file named "<NULL>-qemu-arm.dtb" instead of falling back to using ${fdt_addr}. That bug would need to be fixed first before applying this patch.
Well, and that load will fail and everyone's happy, no?
No, because currently if DTB loading from the filesystem/tftp is attempted and it fails, it aborts the boot. It doesn't matter if it's via a 'FDT' or 'FDTDIR' directive. In the case of typical hardware that's probably the desired behaviour.
I guess the qemu_arm + FDTDIR case can be fixed by not attempting a .dtb load if the default fdtfile is not known due to $soc or $board being unset. At least I doubt that some other board could be relying on a filename containing literally "<NULL>" :)
Well - IIRC $soc and $board should also always be defined ;). So yet another thing to fix in the QEMU port.
See my patch below. Are you happy with it? (qemu-qemu-arm.dtb doesn't make sense to me, though :)
IMHO we should fall back to $fdtcontroladdr always
FWIW, to me the idea of passing $fdtcontroladdr to the OS has always filled me with dread. On top of the usual backwards- and forwards-compatibility problems that happen when mixing and matching kernels and DTBs from different releases, you now have to deal with
That's something that we seriously as a community need to get sorted out. We're pushing hard for it in the EBBR context. The fact that people are afraid of putting *hardware desciption* into their firmware is just mind boggling.
I don't have a strong opinion, but it seems to me that 'fall-back' approach is quite normal. If it doesn't work on a specific board, 'fdt_addr' should be defined.
Thanks, -Takahiro Akashi
issues like U-Boot specific .dts that are majorly diverged from Linux ones, or where the .dts is otherwise from Linux but the U-Boot specific
These case should really be the minority. And if you see those, please fix them.
additions break it for Linux, or where the .dts used is wrong for the
I've never seen a case where a U-Boot addition broke the DT for Linux.
specific hardware revision but close enough for U-Boot's purposes, and so on...
Again, something that just needs fixing. Device trees belong to the entity that knows hardware, not to the OS. Otherwise you lose the abstraction layer that DT gives you and you lose the ability to run "generic" kernels. And of course you break the ecosystem, because now good luck running BSD, your own little toy OS, etc ;)
Alex
===8<=== From 47b26a86359a3b612e890f2ca2d5d20092f9f4e1 Mon Sep 17 00:00:00 2001 From: AKASHI Takahiro takahiro.akashi@linaro.org Date: Fri, 19 Oct 2018 15:22:02 +0900 Subject: [PATCH] arm: qemu: rework Kconfig
Define SYS_SOC and move SYS_* to a canonical place (under board).
Signed-off-by: AKASHI Takahiro takahiro.akashi@linaro.org
Looks good enough to me, but it's up to Tuomas to double check and take as he's the qemu-arm maintainer :).
It also usually helps to post the patch as a new message, not buried inside a thread ;).
Alex