Re: [PATCH v1 12/12] drm/todo: Add bridge related todo items

From: Dave Stevenson <dave.stevenson@raspberrypi.com>
To: Sam Ravnborg <sam@ravnborg.org>
Cc: DRI Development <dri-devel@lists.freedesktop.org>,
	 Andrzej Hajda <andrzej.hajda@intel.com>,
	Neil Armstrong <narmstrong@baylibre.com>,
	 Robert Foss <robert.foss@linaro.org>,
	 Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Jonas Karlman <jonas@kwiboo.se>,
	 Jernej Skrabec <jernej.skrabec@gmail.com>,
	 Dafna Hirschfeld <dafna.hirschfeld@collabora.com>,
	David Airlie <airlied@linux.ie>,
	 Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>,
	Guenter Roeck <groeck@chromium.org>,
	 chrome-platform@lists.linux.dev,
	Chun-Kuang Hu <chunkuang.hu@kernel.org>,
	 Jitao Shi <jitao.shi@mediatek.com>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	 Arnd Bergmann <arnd@arndb.de>,
	linux-mediatek@lists.infradead.org,
	 Matthias Brugger <matthias.bgg@gmail.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	 Philip Chen <philipchen@chromium.org>,
	linux-renesas-soc@vger.kernel.org,
	 Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>,
	 Enric Balletbo i Serra <enric.balletbo@collabora.com>,
	Cai Huoqing <cai.huoqing@linux.dev>
Subject: Re: [PATCH v1 12/12] drm/todo: Add bridge related todo items
Date: Mon, 18 Jul 2022 11:27:37 +0100	[thread overview]
Message-ID: <CAPY8ntB2gXoUbUJhDLWVX3szaEKKKhnOO-qsKRZkMp1jDOt0Qg@mail.gmail.com> (raw)
In-Reply-To: <20220717175801.78668-5-sam@ravnborg.org>

Hi Sam

On Sun, 17 Jul 2022 at 18:58, Sam Ravnborg <sam@ravnborg.org> wrote:
>
> Add todo in the hope someone will help updating the bridge drivers.
>
> v2:
>   - Updated descriptions in todo.rst
>
> Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
> Acked-by: Maxime Ripard <mripard@kernel.org>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> ---
>  Documentation/gpu/todo.rst | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
> index 10bfb50908d1..fbcc232e0bc1 100644
> --- a/Documentation/gpu/todo.rst
> +++ b/Documentation/gpu/todo.rst
> @@ -480,6 +480,26 @@ Contact: Thomas Zimmermann <tzimmermann@suse.de>
>
>  Level: Starter
>
> +Drop use of deprecated operations in bridge drivers
> +--------------------------------------------------
> +
> +&struct drm_bridge_funcs contains a number of deprecated operations
> +which can be replaced by the atomic variants.
> +
> +The following is more or less 1:1 replacements with the arguments
> +and names adjusted:
> +* pre_enable => atomic_pre_enable
> +* enable => atomic_enable
> +* disable => atomic_disable
> +* post_disable => atomic_post_disable
> +
> +* mode_set is no longer required and the implementation shall be merged
> +  with atomic_enable.

The dw-mipi-dsi and msm DSI host controller bridge drivers are
currently relying on mode_set as a convenient hook to power up the DSI
host prior to pre_enable of the bridge chain. Removing it is therefore
going to break those.

There is a proposed mechanism to allow for the removal of this hack
[1], but it's still waiting on R-B tags and/or discussion from bridge
maintainers (gentle nudge as you are one of those maintainers).

And do you mean merge with atomic_enable, or merge with
atomic_pre_enable? atomic_pre_enable would be more applicable for
almost all the bridges I'm aware of as they want to be configured
before video starts.

Cheers,
  Dave

[1] https://lists.freedesktop.org/archives/dri-devel/2022-March/345466.html

> +Contact: bridge maintainers, Sam Ravnborg <sam@ravnborg.org>,
> +         Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> +
> +Level: Beginner or intermediate (depending on the driver)
>
>  Core refactorings
>  =================
> --
> 2.34.1
>