Re: [PATCH v3 5/6] dt-bindings: add the rockchip, dual-channel for dw-mipi-dsi

[Archit Taneja <architt@codeaurora.org>]

On 11/30/2017 11:02 PM, Nickey Yang wrote:
> Hi Archit,
> 
> 
> On 2017年10月26日 12:53, Archit Taneja wrote:
>>
>>
>> On 10/25/2017 09:21 AM, Nickey Yang wrote:
>>> Configure dsi slave channel when driving a panel
>>> which needs 2 DSI links.
>>>
>>> Signed-off-by: Nickey Yang <nickey.yang@rock-chips.com>
>>> ---
>>> .../devicetree/bindings/display/rockchip/dw_mipi_dsi_rockchip.txt | 2 ++
>>>   1 file changed, 2 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/display/rockchip/dw_mipi_dsi_rockchip.txt 
>>> b/Documentation/devicetree/bindings/display/rockchip/dw_mipi_dsi_rockchip.txt
>>> index 6bb59ab..a2bea22 100644
>>> --- a/Documentation/devicetree/bindings/display/rockchip/dw_mipi_dsi_rockchip.txt
>>> +++ b/Documentation/devicetree/bindings/display/rockchip/dw_mipi_dsi_rockchip.txt
>>> @@ -19,6 +19,8 @@ Optional properties:
>>>   - power-domains: a phandle to mipi dsi power domain node.
>>>   - resets: list of phandle + reset specifier pairs, as described in [3].
>>>   - reset-names: string reset name, must be "apb".
>>> +- rockchip,dual-channel: phandle to a 2nd DSI channel, useful as a slave
>>> +channel when driving a panel which needs 2 DSI links.
>> The example below is how dual DSI bindings could look like. Let me know what
>> you think of it.
>>
>> If both DSI outputs drive the same device (i.e, point to the same panel DT
>> node), then I think it's reasonable enough to assume that the DSIs are
>> operating in a 'dual-channel' mode. That being said, we still need DT to
>> describe which of the DSIs generates the clock for both the channels. This
>> is done with the 'clock-master' DT binding.
>>
>> Thanks,
>> Archit
>>
>> mipi_dsi: mipi@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@0 {
>>                 panel_in_channel0: endpoint {
>>                     remote-endpoint = <&mipi_panel_out>;
>>                 };
>>             };
>>
>>             port@1 {
>>                 panel_in_channel1: endpoint {
>>                     remote-endpoint = <&mipi1_panel_out>;
>>                 };
>>
>>             };
>>         };
>>     };
>> };
>>
>>
>> mipi_dsi1: mipi@ff968000 {
>>     ...
>>     ...
>>
>>     ports {
>>         mipi1_in: port {
>>             ...
>>             ...
>>         };
>>
>>         mipi1_out: port {
>>             mipi1_panel_out: endpoint {
>>                 remote-endpoint = <&panel_in_channel1>;
>>             };
>>         };
>>     };
>> };
>>
> I try to follow as you suggested,use
> 
> mipi_dsi: mipi@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@0 {
>                  panel_in_channel0: endpoint {
>                      remote-endpoint = <&mipi_panel_out>;
>                  };
>              };
>              port@1 {
>                  panel_in_channel1: endpoint {
>                      remote-endpoint = <&mipi1_panel_out>;
>                  };
> 
>              };
>          };
>      };
> };
> 
> mipi_dsi1: mipi@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.

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.

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.

> 
> 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.

Archit

> 
> 
> Thanks,
> Nickey
> 
>>>     [1] Documentation/devicetree/bindings/clock/clock-bindings.txt
>>>   [2] Documentation/devicetree/bindings/media/video-interfaces.txt
>>>
>>
> 
> 

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