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Message-ID: <ef60403f-078f-411a-867b-9b551e863f56@linaro.org>
Date: Mon, 3 Jun 2024 15:08:37 +0200
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From: neil.armstrong@linaro.org
Reply-To: neil.armstrong@linaro.org
Subject: Re: [PATCH 00/14] Add initial support for the Rockchip RK3588 HDMI TX
 Controller
To: Heiko Stuebner <heiko@sntech.de>,
 Cristian Ciocaltea <cristian.ciocaltea@collabora.com>,
 Andrzej Hajda <andrzej.hajda@intel.com>, Robert Foss <rfoss@kernel.org>,
 Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
 Jonas Karlman <jonas@kwiboo.se>, Jernej Skrabec <jernej.skrabec@gmail.com>,
 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
 Maxime Ripard <mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de>,
 David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
 Sandy Huang <hjc@rock-chips.com>, Rob Herring <robh@kernel.org>,
 Krzysztof Kozlowski <krzk+dt@kernel.org>, Conor Dooley
 <conor+dt@kernel.org>, Mark Yao <markyao0591@gmail.com>,
 Andy Yan <andy.yan@rock-chips.com>
Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
 linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org,
 devicetree@vger.kernel.org, kernel@collabora.com,
 Alexandre ARNOUD <aarnoud@me.com>, Luis de Arquer <ldearquer@gmail.com>,
 Algea Cao <algea.cao@rock-chips.com>
References: <20240601-b4-rk3588-bridge-upstream-v1-0-f6203753232b@collabora.com>
 <a4b22708-e85d-448a-8145-244b49bca053@linaro.org>
 <ab0a6372-091b-4293-8907-a4b3ff4845c0@rock-chips.com>
 <11359776.NyiUUSuA9g@phil>
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Hi,

On 03/06/2024 15:03, Heiko Stuebner wrote:
> Am Montag, 3. Juni 2024, 14:14:17 CEST schrieb Andy Yan:
>> Hi Neil:
>>
>> On 6/3/24 16:55, Neil Armstrong wrote:
>>> Hi Christian,
>>>
>>> On 01/06/2024 15:12, Cristian Ciocaltea wrote:
>>>> The RK3588 SoC family integrates a Quad-Pixel (QP) variant of the
>>>> Synopsys DesignWare HDMI TX controller used in the previous SoCs.
>>>>
>>>> It is HDMI 2.1 compliant and supports the following features, among
>>>> others:
>>>>
>>> .
>>>
>>> ..
>>>
>>>> * SCDC I2C DDC access
>>>> * TMDS Scrambler enabling 2160p@60Hz with RGB/YCbCr4:4:4
>>>> * YCbCr4:2:0 enabling 2160p@60Hz at lower HDMI link speeds
>>>> * Multi-stream audio
>>>> * Enhanced Audio Return Channel (EARC)
>>> -> Those features were already supported by the HDMI 2.0a compliant HW, just
>>> list the _new_ features for HDMI 2.1
>>>
>>> I did a quick review of your patchset and I don't understand why you need
>>> to add a separate dw-hdmi-qp.c since you only need simple variants of the I2C
>>> bus, infoframe and bridge setup.
>>>
>>> Can you elaborate further ? isn't this Quad-Pixel (QP) TX controller version
>>> detectable at runtime ?
>>>
>>> I would prefer to keep a single dw-hdmi driver if possible.
>>
>>
>>
>> The QP HDMI controller is a completely different variant with totally different
>> registers layout, see PATCH 13/14.
>> I think make it a separate driver will be easier for development and maintenance.
> 
> I'm with Andy here. Trying to navigate a driver for two IP blocks really
> sounds taxing especially when both are so different.

I agree, I just wanted more details than "variant of the
Synopsys DesignWare HDMI TX controller", if the register mapping is 100%
different, and does not match at all with the old IP, then it's indeed time
to make a brand new driver, but instead of doing a mix up, it's time to extract
the dw-hdmi code that could be common helpers into a dw-hdmi-common module
and use them.

As I see, no "driver" code can be shared, only DRM plumbings, so perhaps those
plumbing code should go into the DRM core ?

In any case, please add more details on the cover letter, including the detailed
HW differrence and the design you chose so support this new IP.

Neil

> 
> Synopsis also created a new dsi controller for the DSI2 standard, with
> a vastly different registers layout.
> 
> I guess at some point there is time to say this really is a new IP ;-) .
> 
> 
> Though while on that thought, I don't fully understand why both a compiled
> under the dw_hdmi kconfig symbol. People going for a minimal kernel might
> want one or the other, but not both for their specific board.
> 
> 
> Heiko
> 
>