linux-kernel - Re: [PATCH] drm/bridge_connector: enable HPD by default if supported

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Message-ID: <a7d0b013-6114-07b3-0a7b-0d17db8a3982@cogentembedded.com>
Date:   Mon, 31 Jan 2022 19:38:13 +0300
From:   Nikita Yushchenko <nikita.yoush@...entembedded.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Jacopo Mondi <jacopo+renesas@...ndi.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/bridge_connector: enable HPD by default if supported

>> Hotplug events reported by bridge drivers over drm_bridge_hpd_notify()
>> get ignored unless somebody calls drm_bridge_hpd_enable(). When the
>> connector for the bridge is bridge_connector, such a call is done from
>> drm_bridge_connector_enable_hpd().
>>
>> However drm_bridge_connector_enable_hpd() is never called on init paths,
>> documentation suggests that it is intended for suspend/resume paths.
> 
> Hmmmm... I'm in two minds about this. The problem description is
> correct, but I wonder if HPD should be enabled unconditionally here, or
> if this should be left to display drivers to control.
> drivers/gpu/drm/imx/dcss/dcss-kms.c enables HPD manually at init time,
> other drivers don't.
> 
> It feels like this should be under control of the display controller
> driver, but I can't think of a use case for not enabling HPD at init
> time. Any second opinion from anyone ?

Hi.

Can we somehow move forward here?..