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

[Marek Vasut]

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.

So I don't think any change is needed to this patch ?

> Example OF-graph is on the commit message.
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/gpu/drm/drm_of.c?id=80253168dbfd256bca97cf7f13312863c5a7f2e5

It seems the current upstream DT bindings only support DSI hosts which 
do provide an endpoint, because port at 0 is required per DT binding 
document. If you want to support the other options as listed in the 
aforementioned commit, then you would have to extend this driver and its 
bindings, but that is out of scope of this series.