Re: [PATCH 11/11] ARM: versatile: move CLCD configuration to device tree

On Wed, Feb 17, 2016 at 10:09 AM, Tomi Valkeinen [off-list ref] wrote:

quoted

Tested on Versatile AB with just VGA with the default device tree,
and with the IB2 daughterboard with the custom IB2 device tree.
Tested to shunt in XVGA by modifying the device tree and this works
too. Also tested on QEMU for Versatile in both VGA and Sanyo 2.5"
mode. I don't have the IB1 daughterboard and its add-on displays,
but it should work as long as the detection mechanism and device
tree parameters are sound.

Well... I don't like this very much. The .dts should contain
descriptions for hardware that is connected. Have you looked at DT
overlays? I think they would be a much better match for this.

I'll look into it. I don't know how good those are. They must be overlaid
at runtime and anyways exist somewhere in memory so they can be
overlaid in there.

What's the SYS_CLCD register? An EEPROM or such, programmed when the
board is manufactured? Is the panel meant to be switchable by the user,
possibly to a panel that's not "standard"?

As Russell points out: it's a register that contains a number saying what
panel is connected.

So it is plug-n-play and I want to preserve this in the patch.

The alternative is to make one DTS per display type connected, but that is
loosing all the nice plug'n'play :(

But if an overlay can do the same, I'm game for it.

Yours,
Linus Walleij