Messages in this thread | | | Date | Thu, 18 Jan 2018 08:25:21 +0100 | From | Maxime Ripard <> | Subject | Re: [PATCH v3 09/13] drm/sun4i: backend: Wire in the frontend |
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Hi,
On Wed, Jan 17, 2018 at 09:46:13PM +0800, Chen-Yu Tsai wrote: > > + for_each_available_child_of_node(port, ep) { > > + remote = of_graph_get_remote_port_parent(ep); > > + if (!remote) > > + continue; > > + > > + /* does this node match any registered engines? */ > > + list_for_each_entry(frontend, &drv->frontend_list, list) { > > + if (remote == frontend->node) { > > + of_node_put(remote); > > + of_node_put(port); > > + return frontend; > > + } > > + } > > I assume that since you are only enabling support on the A33, you are > not considering dual display pipeline cases. We have cross connections > in the of graph for those situations, i.e. frontend0 can output to both > backend0 and backend1, as described in the following link: > > http://elixir.free-electrons.com/linux/v4.15-rc8/source/arch/arm/boot/dts/sun6i-a31.dtsi#L1177 > > So with your code, both backends would end up using frontend0, and > if both display pipelines are active, one would potentially step on > the other. > > Instead, have the frontend store its ID in its data structure, and > have the backend look through the list of frontends to find a match > for the backend's ID. This is what we already do for engine <-> TCON: > > http://elixir.free-electrons.com/linux/v4.15-rc8/source/drivers/gpu/drm/sun4i/sun4i_tcon.c#L583 > > Or just leave a TODO note and I can do it later. :)
We discussed it on IRC, and yes, I don't have a test setup right now with two pipelines being used, and there's a few changes that need to be made for it to operate properly on the A10/A20. That's why I only added the A33 in the supported list at the moment.
I'll add a TODO note
> Otherwise, > > Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Thanks! Maxime
-- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com [unhandled content-type:application/pgp-signature] | |