Hi Christopher,
Am Dienstag, den 29.11.2016, 16:45 +0100 schrieb Christopher Spinrath:
> Hi all,
>
> I am trying to enable the second display pipeline of my imx6q based
> Utilite Pro. I appended a devicetree patch to this email for reference.
>
> While it works perfectly on its own there occur kernel warnings (see
> below) if both pipelines are connected. Furthermore, the machine becomes
> almost unresponsive. Note that these warnings start to happen around the
> time getty is started. No other userspace stuff (e.g. X11) is involved.
>
> I can make it work by adding the following hack to the devicetree:
>
> display-subsystem {
> compatible = "fsl,imx-display-subsystem";
> ports = <&ipu1_di0>, <&ipu2_di0>, <&ipu2_di1>, <&ipu1_di1>;
> };
>
> (i.e. reordering the ports of the display-subsystem.)
>
> To my understanding the imx drm driver maps both outputs to ipu1 by
> default which cannot handle the load.
What is the load?
> But using ipu1 and ipu2 for a
> single output each works. Unfortunately, I didn't find a way to model
> this restriction in the devicetree (in a sane way).
You can sever the links between HDMI encoder mux and IPU1 display
interfaces to keep it from being connected to IPU1 DI1:
/delete-node/&ipu1_di0_hdmi;
/delete-node/&hdmi_mux_0;
/delete-node/&ipu1_di1_hdmi;
/delete-node/&hdmi_mux_1;
> IMHO the driver should at least disable one of the outputs instead of
> rendering the whole system unusable. Optimally, it should figure out a
> correct mapping between outputs and ipu's itself.
It should. The problem with the IPU limitations is that they are
cross-crtc. The reference manual says that the maximum combined rate for
both display interfaces in an IPU is 240 MP/s, so we'd need to take into
account the pixel clocks of already enabled sibling crtcs when deciding
whether a mode can be set.
regards
Philipp
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