Hi Archit,
I'm a relative n00b here, but I'm trying to follow along and I have some
questions:
On Fri, Dec 01, 2017 at 06:29:04PM +0530, Archit Taneja wrote:
> On 11/30/2017 11:02 PM, Nickey Yang wrote:
> >I try to follow as you suggested,use
> >
> >mipi_dsi: mipi at ff960000 {
> > ??? ...
> > ??? ...
> > ??? clock-master;??? /* implies that this DSI instance drivers the clock
> > ??? ??? ??? ?* for both the DSIs.
> > ??? ??? ??? ?*/
> > ??? ports {
> > ??? ??? mipi_in: port {
> > ??? ??? ??? ...
> > ??? ??? ??? ...
> > ??? ??? };
> > ??? ??? /* add extra output ports for both DSIs */
> > ??? ??? mipi_out: port {
> > ??? ??? ??? mipi_panel_out: endpoint {
> > ??? ??? ??? ??? remote-endpoint = <&panel_in_channel0>;
> > ??? ??? ??? };
> > ??? ??? };
> > ??? };
> > ??? panel {
> > ??? ??? ...
> > ??? ??? ...
> > ??? ??? /*
> > ??? ??? ?* panel node can describe its input ports, if both the DSIs output
> > ??? ??? ?* ports are connected to the same device (i.e, the same DSI panel),
> > ??? ??? ?* we can assume that the DSIs need to operate in dual DSI mode
> > ??? ??? ?*/
> > ??? ??? ports {
> > ??? ??? ??? ...
> > ??? ??? ??? port at 0 {
> > ??? ??? ??? ??? panel_in_channel0: endpoint {
> > ??? ??? ??? ??? ??? remote-endpoint = <&mipi_panel_out>;
> > ??? ??? ??? ??? };
> > ??? ??? ??? };
> > ??? ??? ??? port at 1 {
> > ??? ??? ??? ??? panel_in_channel1: endpoint {
> > ??? ??? ??? ??? ??? remote-endpoint = <&mipi1_panel_out>;
> > ??? ??? ??? ??? };
> >
> > ??? ??? ??? };
> > ??? ??? };
> > ??? };
> >};
> >
> >mipi_dsi1: mipi at ff968000 {
> > ??? ...
> > ??? ...
> > ??? ports {
> > ??? ??? mipi1_in: port {
> > ??? ??? ??? ...
> > ??? ??? ??? ...
> > ??? ??? };
> > ??? ??? mipi1_out: port {
> > ??? ??? ??? mipi1_panel_out: endpoint {
> > ??? ??? ??? ??? remote-endpoint = <&panel_in_channel1>;
> > ??? ??? ??? };
> > ??? ??? };
> > ??? };
> >}
> >
> >But it seems we can not use of_drm_find_panel(like below)
> >
> >/*
> > ??????? port = of_graph_get_port_by_id(dev->of_node, 1);
> > ??????? if (port) {
> > ??????????????? endpoint = of_get_child_by_name(port, "endpoint");
> > ??????????????? of_node_put(port);
> > ??????????????? if (!endpoint) {
> > ??????????????????????? dev_err(dev, "no output endpoint found\n");
> > ??????????????????????? return -EINVAL;
> > ??????????????? }
> > ??????????????? panel_node = of_graph_get_remote_port_parent(endpoint);
> > ??????????????? of_node_put(endpoint);
> > ??????????????? if (!panel_node) {
> > ??????????????????????? dev_err(dev, "no output node found\n");
> > ??????????????????????? return -EINVAL;
> > ??????????????? }
> > ??????????????? panel = of_drm_find_panel(panel_node);
> > ??????????????? of_node_put(panel_node);
> > ??????????????? if (!panel)
> > ??????????????????????? return -EPROBE_DEFER;
> > ??????? }
> >*/
> >to get DSI1 outputs,because of_drm_find_panel need compare
> >
> >if (panel->dev->of_node == np)
> >
> >in dsi_panel driver innolux->base.dev = &innolux->link->dev;
> >dsi->dev
>
> Yes, we should only have 1 drm_panel in the global panel list.
> Shouldn't it be possible to modify the dsi driver such that dsi1
> doesn't care whether it has a drm_panel for it or not, if we are
> in dual dsi mode?
>
> I imagine a sequence like this:
>
> 1. dsi0 probes, parses the of-graph, finds the panel and saves its device
> node.
Does this mean we depend on probe order? Or would we be able to
-EPROBE_DEFER or similar if dsi1 binds first?
> 2. dsi1 probes, parses the of-graph, find the panel's device node
> - dsi1 checks if it is the same as the panel attached to dsi0.
> - If so, it just takes the drm_panel pointer from dsi0.
> - If not, it tries a of_drm_find_panel() on the panel's device node.
So, that all means we'd need a new variant of
drm_of_find_panel_or_bridge() for "dual" drivers like this? Or else
open-code this logic in dw-mipi-dsi.c?
> A dual DSI panel driver would also be a bit different. It will be a
> mipi_dsi_driver with the master DSI (dsi0) as the mipi_dsi_device. Using
> the of-graph helpers, we would get the device node of dsi1 using
> of_find_mipi_dsi_host_by_node(), and create another DSI device using
> mipi_dsi_device_register_full(). Then, we call mipi_dsi_attach() on
> both the dsi devices.
That seems...interesting. I guess that sounds like it could work, but
someone would have to play with that a bit more.
I assume one wouldn't want to do all this in every dual DSI driver that
needs this, right?
> >struct innolux_panel {
> > ??????? struct drm_panel base;
> > ??????? struct mipi_dsi_device *link;
> >};
> >It means one panel can only be found in his dsi node,(like dsi0 above).
> >
> >I'm doubting about it, Or? may we follow tegra_dsi_ganged_probe
> >(drivers/gpu/drm/tergra/dsi.c) method.
>
> This method will add a new binding similar to "nvidia,ganged-mode", which
> is something we don't want to do.
It's unfortunate we have the anti-pattern already merged :(
Brian
