On Thu, Feb 29, 2024 at 11:17:28AM +0530, Sumit Garg wrote:
On Wed, 28 Feb 2024 at 20:50, Tom Rini trini@konsulko.com wrote:
On Wed, Feb 28, 2024 at 07:44:42PM +0530, Sumit Garg wrote:
- Shawn, Krzysztof, Conor
Hi Tom,
On Wed, 28 Feb 2024 at 18:40, Tom Rini trini@konsulko.com wrote:
On Wed, Feb 28, 2024 at 10:09:13AM +0300, Dan Carpenter wrote:
On Tue, Feb 27, 2024 at 04:40:01PM +0100, Sébastien Szymanski wrote:
Commit 5d7a95f49999 ("imx6ul/imx6ull: synchronise device trees with linux") removed the display timings from the board device tree whereas they are still needed by the mxsfb driver. Add the timings back (the correct ones) in the imx6ul-opos6uldev-u-boot.dtsi file and remove them from the opos6uldev.env file.
Update the opos6uldev_defconfig file so that the LCD turns on at boot.
Fixes: 5d7a95f49999 ("imx6ul/imx6ull: synchronise device trees with linux") Signed-off-by: Sébastien Szymanski sebastien.szymanski@armadeus.com
Huh. This is the commit that did that upstream.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
It's interesting how the timings in linux were always slightly different from in u-boot.
Thanks for tracking that down, Dan. I'm adding in Sumit and Rob here because this is a recent (rather than ancient) example of one of the concerns about OF_UPSTREAM.
I rather think about this as an opportunity to improve with OF_UPSTREAM. We can feed these kinds of DT ABI breakages to corresponding Linux kernel sub-arch maintainers. Especially once we move to OF_UPSTREAM and a sub-arch maintainer profile in Linux kernel to keep them aware that U-Boot should be considered too.
Yes, a more extensive check around when removing information from dts files would be good.
I think the commit in question can be summarized as "remove a bunch of explicit HW information because there's now a Linux Kernel driver that determines that dynamically". What do we do next? The old information is in a presumably valid binding still, can we just put it back and comment that consumers outside of Linux use this still so it's not removed again later? Or am I just missing where we can instead get this information from the DT still and not need to come up with a new driver and subsystems?
I can see following two paths forward:
- Partially revert the Linux kernel commit to add back the display
timings in DT. 2) Extend drivers/video/simple_panel.c in U-Boot to add support for compatible: "armadeus,st0700-adapt".
If possible then I would be in favour of (2) rather than the current patch to do this properly.
Well, looking at the kernel drivers/gpu/drm/panel/panel-simple.c driver and then our drivers/video/simple_panel.c it sure would be nice if it's just a matter of adding a compatible but I wouldn't be surprised if it ends up needing more information being passed along too?
Although I am not a LCD panel expert but looking at the kernel driver code [1], the display timings are rather taken from a static data structure matching the compatible "armadeus,st0700-adapt".
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/driv...
Yes. My point is that it seems like the situation changed from "device tree provides timings for the platform" to "driver has timing information for N displays" and so we'll need to do something clever to avoid including the structs for 5 panels when we'll only ever (likely...) see one. And that also yes, we'll probably need to add data for this panel rather than re-use the PANASONIC_VVX10F004B00 data.
And I'm going assume there's good reasons for the design change in how the drivers work in Linux now and note that it might make things more challenging for us when we do care about space.
I agree it is always going to be challenging to use DT during SPL stage which is mostly constrained by limited on-chip RAM.
Well, no. The DT way handled this more efficiently, I think I wasn't clear enough in my reply.