linux-kernel - Re: [PATCH v2 4/6] drm/meson: encoder_hdmi: switch to bridge DRM_BRIDGE_ATTACH_NO

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Message-ID: <9cba6fbf-a8f7-4831-5774-1e270932816d@baylibre.com>
Date:   Mon, 18 Oct 2021 09:50:00 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     daniel@...ll.ch, Laurent.pinchart@...asonboard.com,
        sam@...nborg.org, dri-devel@...ts.freedesktop.org,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/6] drm/meson: encoder_hdmi: switch to bridge
 DRM_BRIDGE_ATTACH_NO_CONNECTOR

Hi,

On 16/10/2021 00:07, Martin Blumenstingl wrote:
> Hi Neil,
> 
> On Fri, Oct 15, 2021 at 4:11 PM Neil Armstrong <narmstrong@...libre.com> wrote:
>>
>> This implements the necessary change to no more use the embedded
>> connector in dw-hdmi and use the dedicated bridge connector driver
>> by passing DRM_BRIDGE_ATTACH_NO_CONNECTOR to the bridge attach call.
>>
>> The necessary connector properties are added to handle the same
>> functionalities as the embedded dw-hdmi connector, i.e. the HDR
>> metadata, the CEC notifier & other flags.
>>
>> The dw-hdmi output_port is set to 1 in order to look for a connector
>> next bridge in order to get DRM_BRIDGE_ATTACH_NO_CONNECTOR working.
>>
>> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
>> Acked-by: Sam Ravnborg <sam@...nborg.org>
> another great piece which helps a lot with HDMI support for the 32-bit SoCs!
> I have one question below - but regardless of the answer there this gets my:
> Acked-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> 
> [...]
>> +       pdev = of_find_device_by_node(remote);
> I am wondering if we should use something like:
>     encoder_hdmi->cec_notifier_pdev
> 
>> +       if (pdev) {
>> +               struct cec_connector_info conn_info;
>> +               struct cec_notifier *notifier;
>> +
>> +               cec_fill_conn_info_from_drm(&conn_info, meson_encoder_hdmi->connector);
>> +
>> +               notifier = cec_notifier_conn_register(&pdev->dev, NULL, &conn_info);
>> +               if (!notifier)
>> +                       return -ENOMEM;
>> +
>> +               meson_encoder_hdmi->cec_notifier = notifier;
>> +       }
> and then move this logic to meson_encoder_hdmi_attach()

We can't because we create the connector after the attach.

> This would be important if .detach() and .attach() can be called
> multiple times (for example during suspend and resume). But I am not
> sure if that's a supported use-case.

Attach for now will only be done once at probe, and detach only a remove,
we don't change the bridge chaining while suspend/resume, we only reset the
pipeline state and put the old state back when resuming.

Neil

> 
> 
> Best regards,
> Martin
>