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Message-ID: <5a1df5ce-a497-760b-8e2c-130a0e659c0b@gmail.com>
Date:   Mon, 15 Aug 2022 03:15:56 +0300
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Subject: Re: [PATCH] drm/bridge: sii902x: add support for
 DRM_BRIDGE_ATTACH_NO_CONNECTOR
Content-Language: en-US
To:     Neil Armstrong <narmstrong@baylibre.com>, andrzej.hajda@intel.com,
        robert.foss@linaro.org, Linus Walleij <linus.walleij@linaro.org>,
        Rob Herring <robh+dt@kernel.org>
Cc:     jernej.skrabec@gmail.com, jonas@kwiboo.se,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        Laurent.pinchart@ideasonboard.com
References: <20220113144305.1074389-1-narmstrong@baylibre.com>
 <25976b46-21b4-6e3f-0182-85dd4ca2b654@gmail.com>
 <a4a36360-3f77-17a0-9239-08cb8c08de74@baylibre.com>
 <13bd6440-9a61-d444-518c-f4e8cba0b825@baylibre.com>
From:   Dmitry Osipenko <digetx@gmail.com>
In-Reply-To: <13bd6440-9a61-d444-518c-f4e8cba0b825@baylibre.com>
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08.08.2022 12:51, Neil Armstrong пишет:
> On 08/08/2022 11:15, Neil Armstrong wrote:
>> Hi Dmitry,
>>
>> On 31/07/2022 22:07, Dmitry Osipenko wrote:
>>> 13.01.2022 17:43, Neil Armstrong пишет:
>>>> This adds support for DRM_BRIDGE_ATTACH_NO_CONNECTOR by adding the
>>>> bridge get_edid() and detect() callbacks after refactoring the
>>>> connector
>>>> get_modes() and connector_detect() callbacks.
>>>>
>>>> In order to keep the bridge working, extra code in get_modes() has been
>>>> moved to more logical places.
>>>>
>>>> Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
>>>> ---
>>>>   drivers/gpu/drm/bridge/sii902x.c | 129
>>>> ++++++++++++++++++++++++-------
>>
>> 1 file changed, 99 insertions(+), 30 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/bridge/sii902x.c
>>>> b/drivers/gpu/drm/bridge/sii902x.c
>>>> index 89558e581530..65549fbfdc87 100644
>>>> --- a/drivers/gpu/drm/bridge/sii902x.c
>>>> +++ b/drivers/gpu/drm/bridge/sii902x.c
> 
> [...]
> 
>>>>       }
>>>> +    endpoint = of_graph_get_endpoint_by_regs(dev->of_node, 1, -1);
>>>> +    if (endpoint) {
>>>> +        struct device_node *remote =
>>>> of_graph_get_remote_port_parent(endpoint);
>>>> +
>>>> +        of_node_put(endpoint);
>>>> +        if (!remote) {
>>>> +            dev_err(dev, "Endpoint in port@1 unconnected\n");
>>>> +            return -ENODEV;
>>>> +        }
>>>> +
>>>> +        if (!of_device_is_available(remote)) {
>>>> +            dev_err(dev, "port@1 remote device is disabled\n");
>>>> +            of_node_put(remote);
>>>> +            return -ENODEV;
>>>> +        }
>>>> +
>>>> +        sii902x->next_bridge = of_drm_find_bridge(remote);
>>>> +        of_node_put(remote);
>>>> +        if (!sii902x->next_bridge)
>>>> +            return -EPROBE_DEFER;
>>>
>>> Hi,
>>>
>>> This patch broke ARM/QEMU vexpress display because of_drm_find_bridge()
>>> always fail with -EPROBE_DEFER. Reverting this patch returns display
>>> back. Please fix or revert, thanks in advance.
>>
>> Can you share a QEMU cmdline to reproduce ?
> 
> Actually the vexpress DT has multiple input ports instead of a single
> input port at @0
> and an output port at @1 like documented in the bindings:
> 
> vexpress-v2m.dtsi#L303-L307:
> ports {
>     #address-cells = <1>;
>     #size-cells = <0>;
> 
>     /*
>      * Both the core tile and the motherboard routes their output
>      * pads to this transmitter. The motherboard system controller
>      * can select one of them as input using a mux register in
>      * "arm,vexpress-muxfpga". The Vexpress with the CA9 core tile is
>      * the only platform with this specific set-up.
>      */
>     port@0 {
>         reg = <0>;
>         dvi_bridge_in_ct: endpoint {
>             remote-endpoint = <&clcd_pads_ct>;
>         };
>     };
>     port@1 {
>         reg = <1>;
>         dvi_bridge_in_mb: endpoint {
>             remote-endpoint = <&clcd_pads_mb>;
>         };
>     };
> };
> 
> bindings:
>   ports:
>     $ref: /schemas/graph.yaml#/properties/ports
> 
>     properties:
>       port@0:
>         $ref: /schemas/graph.yaml#/properties/port
>         description: Parallel RGB input port
> 
>       port@1:
>         $ref: /schemas/graph.yaml#/properties/port
>         description: HDMI output port
> 
>       port@3:
>         $ref: /schemas/graph.yaml#/properties/port
>         description: Sound input port
> 
> The patch is conform to the bindings, the DT was working but is actually
> not valid.

I haven't looked closely at how to fix this properly, but if we can fix
it using of_machine_is_compatible("arm,vexpress") workaround in the
driver, then it will be good enough at least as a temporal fix, IMO.