[PATCH V3 05/13] drm: bridge: icn6211: Add DSI lane count DT property parsing

[Marek Vasut]

On 3/8/22 13:51, Maxime Ripard wrote:
> On Tue, Mar 08, 2022 at 11:29:59AM +0100, Marek Vasut wrote:
>> On 3/8/22 11:07, Jagan Teki wrote:
>>> On Tue, Mar 8, 2022 at 3:19 PM Marek Vasut <marex at denx.de> wrote:
>>>>
>>>> On 3/8/22 09:03, Jagan Teki wrote:
>>>>
>>>> Hi,
>>>>
>>>> [...]
>>>>
>>>>>> @@ -314,7 +321,9 @@ static const struct drm_bridge_funcs chipone_bridge_funcs = {
>>>>>>     static int chipone_parse_dt(struct chipone *icn)
>>>>>>     {
>>>>>>            struct device *dev = icn->dev;
>>>>>> +       struct device_node *endpoint;
>>>>>>            struct drm_panel *panel;
>>>>>> +       int dsi_lanes;
>>>>>>            int ret;
>>>>>>
>>>>>>            icn->vdd1 = devm_regulator_get_optional(dev, "vdd1");
>>>>>> @@ -350,15 +359,42 @@ static int chipone_parse_dt(struct chipone *icn)
>>>>>>                    return PTR_ERR(icn->enable_gpio);
>>>>>>            }
>>>>>>
>>>>>> +       endpoint = of_graph_get_endpoint_by_regs(dev->of_node, 0, 0);
>>>>>> +       dsi_lanes = of_property_count_u32_elems(endpoint, "data-lanes");
>>>>>> +       icn->host_node = of_graph_get_remote_port_parent(endpoint);
>>>>>> +       of_node_put(endpoint);
>>>>>> +
>>>>>> +       if (!icn->host_node)
>>>>>> +               return -ENODEV;
>>>>>
>>>>> The non-ports-based OF graph returns a -19 example on the Allwinner
>>>>> Display pipeline in R16 [1].
>>>>>
>>>>> We need to have a helper to return host_node for non-ports as I have
>>>>> done it for drm_of_find_bridge.
>>>>>
>>>>> [1] https://patchwork.amarulasolutions.com/patch/1805/
>>>>
>>>> The link points to a patch marked "DO NOT MERGE", maybe that patch is
>>>> missing the DSI host port at 0 OF graph link ? Both port at 0 and port at 1 are
>>>> required, see:
>>>>
>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/display/bridge/chipone,icn6211.yaml#n53
>>>>
>>>> What is "non-ports-based OF graph" ?
>>>>
>>>> I don't see drm_of_find_bridge() in linux-next , what is that ?
>>>
>>> port at 0 is optional as some of the DSI host OF-graph represent the
>>> bridge or panel as child nodes instead of ports. (i think dt-binding
>>> has to fix it to make port at 0 optional)
>>
>> The current upstream DT binding document says:
>>
>>      required:
>>        - port at 0
>>        - port at 1
>>
>> So port at 0 is mandatory.
> 
> In the binding, sure, but fundamentally the DT excerpt Jagan provided is
> correct. If the bridge supports DCS, there's no reason to use the OF
> graph in the first place: the bridge node will be a child node of the
> MIPI-DSI controller (and there's no obligation to use the OF-graph for a
> MIPI-DSI controller).
> 
> I believe port at 0 should be made optional (or downright removed if
> MIPI-DCS in the only control bus).

That's out of scope of this series anyway, so Jagan can implement 
patches for that mode if needed.