drm/bridge: Synopsys DW-HDMI bridge driver for the Ingenic JZ4780 (was Re: Specialising the Synopsys DW-HDMI bridge driver for the Ingenic JZ4780)

[Ezequiel Garcia]

On Thu, 20 Aug 2020 at 19:49, Paul Boddie <paul at boddie.org.uk> wrote:
>
> On Thursday, 20 August 2020 10:19:45 CEST H. Nikolaus Schaller wrote:
> >
> > Yes, it works!!!
>
> It still doesn't work for me. I still get "Input not supported" from my
> monitor. It is a DVI monitor connected via a HDMI adapter, but EDID probing
> works and, as I noted previously, the HDMI/LCDC can be made to work (and
> obviously did work in the 3.18 kernel).
>

This means the dw_hdmi encoder driver is still not good enough
to support your adapter. I haven't yet compared v3.18 vendor
with our version, but I'm afraid that the dw_hdmi stack has
probably changed quite a bit, so a comparison will be difficult.

The natural debug path for me would be to checkout v3.18,
connect your DVI monitor and make a dump of all the
dw_hdmi registers, then make the same dump for our
mainline kernel -- making sure we are comparing the same
mode.

> I used my usual recipe for kernel compilation:
>
> ARCH=mips CROSS_COMPILE=mipsel-linux-gnu- make ci20_defconfig
> ARCH=mips CROSS_COMPILE=mipsel-linux-gnu- make menuconfig
> ARCH=mips CROSS_COMPILE=mipsel-linux-gnu- make -j8 uImage
> ARCH=mips CROSS_COMPILE=mipsel-linux-gnu- make -j8 modules
> ARCH=mips CROSS_COMPILE=mipsel-linux-gnu- make -j8 dtbs
> sudo sh -c 'INSTALL_MOD_PATH=nn ARCH=mips CROSS_COMPILE=mipsel-linux-gnu- \
>             make modules_install'
> sudo sh -c 'INSTALL_PATH=nn/boot ARCH=mips CROSS_COMPILE=mipsel-linux-gnu- \
>             make dtbs_install'
> sudo cp arch/mips/boot/uImage nn/boot/
>
> This was with a snapshot archive made from the following changeset:
>
> b911b4883bfe4f7fa753ac2ff42b25fa6b3055e2
>
> I downloaded it from here:
>
> https://gitlab.collabora.com/linux/0day/-/tree/jz4780-drm-hdmi-v5.9-rc1
>
> (I was going to clone the repository late last night, but it was taking a long
> time and I also didn't want to clone everything yet again.)
>

If you want to avoid cloning the same things over and over
you can use git-clone --reference. And if you want to checkout
just a single branch, git now has --single-branch.

For instance, (assuming a torvalds/ local repo):

git clone -b letux/jz4780-hdmi-v4 --single-branch
git://git.goldelico.com/letux-kernel.git --reference torvalds/ letux

> > There are some unexpected things related to CONFIG settings on my setup
> > (maybe missing modules) but for the first time I can see the boot log on the
> > panel.
> > > This needs some more investigation, but seems at least a good start.
> >
> > Yes it is!
> >
> > I can now git diff the code and the CONFIG.
> >
> > So it seems we have indeed a breakthrough.
> >
> > Thanks to all who did contribute (even behind the scenes in the DRM
> > subsystem), Nikolaus
>
> Before trying this new branch, I did try and tidy up the branch I had been
> working on. I didn't notice all the changes and the new ingenic-drm-drv.c
> file, having assumed that not much would have changed in the DRM driver.
>
> Nevertheless, my attempts at integrating the different branches can be found
> in the paulb-jz4780-ci20-hdmi-5.9-rc1 branch, mentioned earlier.
>
> It would be nice to reconcile the JZ4780 support with the evolving upstream
> support, accommodating the extended descriptors and the extra register usage.
>

I think that's already done in the patches I've cleaned up.
The only thing left to check is plane offset and overlay enablement.

> Paul
>
> P.S. I noticed a few problems with the 5.9-rc1 branches such as powering down
> not actually removing the power and, in my own branch, networking not working
> reliably (or maybe even at all), with the tedious progress indicator never
> terminating in the boot sequence. So, once again, it is another case of half a
> step forwards and about three steps back.
>

Life (and kernel) is like this: sometimes you need to take three steps
back to make a jump forward :-)