On Fri, Mar 01, 2024 at 10:17:35AM +0100, Sébastien Szymanski wrote:
On 3/1/24 07:02, Sumit Garg wrote:
On Thu, 29 Feb 2024 at 19:31, Tom Rini trini@konsulko.com wrote:
On Thu, Feb 29, 2024 at 08:42:42AM -0500, Tom Rini wrote:
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: > > 1) 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.
And it's not just SPL, full U-Boot needs to stay small and within flash partition considerations and I become cranky and question people when non-generic changes impact platforms that don't need the change.
Okay I can see your point. I suppose this leads us to option (1) to partially revert the Linux kernel commit [1] to add back the display timings in DT. Ironically all the folks (developer, U-Boot and Linux kernel iMX maintainers) were involved in the upstream process for the Linux kernel commit [1] under question. So I will let them chime in too.
It is also now possible to have the display timings under the panel node:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/dr...
Not sure if that could help here.
So yes, this in conjunction with https://lore.kernel.org/linux-arm-kernel/20200115123401.2264293-4-oleksandr.... type changes is what I would like to only support in U-Boot going forward (and our drivers/video/simple_panel.c will need an update). This should help make sure we don't have the problem of "new panel, more size growth for every platform".