On 11/07/2025, Ahmad Fatoum wrote: > Hi, Hi,
> > On 04.11.25 21:44, Fabio Estevam wrote: >> On Mon, Oct 20, 2025 at 11:53 PM Liu Ying <[email protected]> wrote: >>> On 10/20/2025, Fabio Estevam wrote: >>>> On Tue, Oct 14, 2025 at 1:12 AM Liu Ying <[email protected]> wrote: >>>> >>>>> Strictly speaking, I don't think i.MX6SX LCDIF is compatible with i.MX28 >>>>> LCDIF >>>>> because at least i.MX28 LCDIF has the version and debug{0,1,2} >>>>> registers(at >>>>> 0x1c0, 0x1d0, 0x1e0 and 0x1f0) while i.MX6SX LCDIF hasn't. > > Thanks for pointing this out. In my opinion, these registers are auxiliary > and don't really change the compatibility situation as a functional driver > can be written without their use, evidenced by the Linux driver doing just > fine without using these registers. DT bindings should after all describe hardwares and in theory they should not consider software implementation, that's why I said 'strictly speaking'. People may argue that potential software would access those "auxiliary" registers and hence i.MX28 LCDIF is not a fallback for i.MX6SX LCDIF. And, to me, register at 0x1e0, i.e., HW_LCDIF_DEBUG1 is not that "auxiliary" at least for Linux, because Linux DRM supports getting current display scanout position to generate accurate vblank timestamp. HW_LCDIF_DEBUG1 actually provides the interface to read scanout position. https://elixir.bootlin.com/linux/v6.18-rc1/source/include/drm/drm_modeset_helper_vtables.h#L448 > >>>> There are some DT users, such as Barebox that matches against >>>> fsl,imx28-lcdif, so we cannot remove it. >>> >>> Hmmm, it looks like software projects like Barebox don't really follow this >>> DT >>> binding. Is it possible to fix Barebox to avoid changing this DT binding by >>> this patch? I'm assuming that Uboot has already been fixed. >>> What do you think? > > I am sorry my prior feedback ended up stalling this series. > > There is a lot of regressions happening due to upstream DT changes and I am > just trying to raise awareness. Another example I stumbled over today: > https://lore.kernel.org/all/[email protected]/ > > > I have submitted a patch[1] to barebox adding explicit i.MX6 SoloX support, > so, having expressed my opinion above, please proceed as you see fit. Fabio, it seems after Barebox is fixed, you can fix the LCDIF compatible strings in imx6sx.dtsi? I don't know if there is any other software project which is taking fsl,imx28-lcdif as a fallback for i.MX6SX LCDIF... > > [1]: > https://lore.barebox.org/barebox/[email protected]/ > > Cheers, > Ahmad > >> >> Thanks >> > > -- Regards, Liu Ying
