[PATCH 2/2] RFC: drm/pl111: Support using the VGA bridge as fallback

[Linus Walleij]

On Mon, Sep 4, 2017 at 11:51 AM, Laurent Pinchart
<laurent.pinchart at ideasonboard.com> wrote:
> On Monday, 4 September 2017 10:43:55 EEST Daniel Vetter wrote:
>> On Fri, Sep 01, 2017 at 11:46:29AM +0200, Linus Walleij wrote:

>> Wrt the more general problem: They way we solve this in the i915 atomic
>> framework is that the various ->fixup calls fill out relevant fields in
>> the drm_crtc_state. I guess we could add an ->atomic_check to bridges, add
>> a bus_flags to drm_crtc_state (or maybe just let everyone patch up
>> adjusted_mode->flags) instead?
>
> Furthermore, if we needed to have access to the connector in the display
> controller driver, this would call for creating the connector there, not in
> the bridge driver. I've advocated this for a long time, and still haven't
> given up all hopes of fixing it.

Hm as it is I am trying to adopt to circumstances, so I was just asked
to replace the custom connector with the generic panel bridge.
(bridge/panel.c)

Then we get the connector out of the generic panel bridge by just
dereferencing panel->connector, this is what the PL111 driver
is already doing for panels since its inception.

Maybe that is wrong, I don't know :/

But like Eric says, the core problem is that the display driver
say enable function needs to know the flags of what it should
output. This driver looks at

connector->display_info.bus_flags & DRM_BUS_FLAG_DE_LOW
connector->display_info.bus_flags & DRM_BUS_FLAG_PIXDATA_NEGEDGE

So the bus flags really need to be available somehow.
I am doing it by keeping a local reference to the connector
in the driver state container.

I tried to dereference the connector from from the pipe at one
point, passing NULL to  but it didn't work out, it seems like
struct drm_simple_display_pipe_funcs
.enable() is called before attaching the connector or something
but I guess I should look closer.

Yours,
Linus Walleij