[RFCv1 11/42] ARM: dts: omap: add channel to DSI panels

[Sebastian Reichel]

Hi,

On Mon, Nov 18, 2019 at 03:37:12PM +0100, H. Nikolaus Schaller wrote:
> > Am 18.11.2019 um 15:33 schrieb Sebastian Reichel <sebastian.reichel at collabora.com>:
> > On Mon, Nov 18, 2019 at 03:05:07PM +0200, Tomi Valkeinen wrote:
> >> On 17/11/2019 04:39, Sebastian Reichel wrote:
> >>> The standard binding for DSI requires, that the channel number
> >>> of the panel is encoded in DT. This adds the channel number in
> >>> all OMAP3-5 boards, in preparation for using common infrastructure.
> >>> 
> >>> Signed-off-by: Sebastian Reichel <sebastian.reichel at collabora.com>
> >>> ---
> >>>  .../devicetree/bindings/display/panel/panel-dsi-cm.txt      | 4 +++-
> >>>  arch/arm/boot/dts/omap3-n950.dts                            | 3 ++-
> >>>  arch/arm/boot/dts/omap3.dtsi                                | 3 +++
> >>>  arch/arm/boot/dts/omap4-droid4-xt894.dts                    | 3 ++-
> >>>  arch/arm/boot/dts/omap4-sdp.dts                             | 6 ++++--
> >>>  arch/arm/boot/dts/omap4.dtsi                                | 6 ++++++
> >>>  arch/arm/boot/dts/omap5.dtsi                                | 6 ++++++
> >>>  7 files changed, 26 insertions(+), 5 deletions(-)
> >> 
> >> Is this required only in the .txt, or also by the driver? This does break
> >> backward compatibility with the dtbs, and there's always someone who won't
> >> like it.
> > 
> > I add a compatible string for the Droid 4 panel in addition to the
> > generic one, which is not really required and just a precaution in
> > case we need some quirks in the future.
> > 
> > But I had to add the DSI channel to DT, which is required to follow
> > the standard DSI bindings. We cannot use the generic infrastructure
> > without this change. Technically it should have been there all the
> > time, it is only working because it is currently hardcoded to 0 in
> > the panel driver.
> 
> Is it possible to change it to default to channel <0> if reg is not
> specified?

Currently nodes without reg property are skipped by of_mipi_dsi_device_add()
and of_mipi_dsi_device_add() fails if reg node is missing. Technically
it should be possible to default to channel 0 there. That affects all
platforms, though. Considering the small amount of boards affected, I think
its better to just fix the DT. Also the fixed DT does not make problems
with older kernels and can be backported.

> > TLDR: Yes, it is required by the driver and it does break backward
> > compatibility for N950 (panel does not yet work on mainline, since
> > the OMAP3 quirks are missing in the omapdrm DSI code), omap4-sdp (
> > untested, I do not know if its working) and Droid 4 (known to be
> > working with current mainline code, most likely people update their
> > DT anyways).

-- Sebastian
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