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Date: Thu, 9 May 2024 15:12:44 +0200
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Subject: Re: [PATCH v2 0/7] Add DSI support for RK3128
From: Alex Bee <knaerzche@gmail.com>
To: =?UTF-8?Q?Heiko_St=C3=BCbner?= <heiko@sntech.de>,
 Andy Yan <andy.yan@rock-chips.com>
Cc: dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org,
 linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org,
 linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org,
 sebastian.reichel@collabora.com, Sandy Huang <hjc@rock-chips.com>,
 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
 Daniel Vetter <daniel@ffwll.ch>, Maxime Ripard <mripard@kernel.org>,
 Conor Dooley <conor+dt@kernel.org>, Rob Herring <robh@kernel.org>,
 Thomas Zimmermann <tzimmermann@suse.de>, David Airlie <airlied@gmail.com>,
 Michael Turquette <mturquette@baylibre.com>, Stephen Boyd <sboyd@kernel.org>
References: <20240509120715.86694-1-knaerzche@gmail.com>
 <38423821.XM6RcZxFsP@diego> <1190cfb6-e2d1-4910-ad57-f7566343ff19@gmail.com>
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Am 09.05.24 um 14:43 schrieb Alex Bee:

> Hi Heiko
>
> Am 09.05.24 um 14:21 schrieb Heiko Stübner:
>> Hi Alex,
>>
>> Am Donnerstag, 9. Mai 2024, 14:07:08 CEST schrieb Alex Bee:
>>> This series aims to add support for the DesignWare MIPI DSI 
>>> controller and
>>> the Innoslicon D-PHY found in RK3128 SoCs. The code additions are 
>>> rather
>>> tiny: It only need some code in the Rockchip dw-mipi-dsi glue layer for
>>> this SoC, add support for an additional clock and do some changes in 
>>> the
>>> SoC's clock driver. Support for the phy was already added when the
>>> Innosilicon D-PHY driver was initially submitted. I tested it with a
>>> 800x1280 DSI panel where all 4 lanes that are supported are used.
>>>
>>> changes in v2:
>>>    To improve power-efficiency when the DSI controller is not in use, I
>>>    dropped the patch which made hclk_vio_h2p a critical clock and 
>>> instead
>>>    added support for an AHB clock to the DSI controller driver and 
>>> updated
>>>    the bindings and the addition to the SoC DT accordingly.
>> The naming already suggests that hclk_vio_h2p is not a clock-part of
>> the actual dsi controller, but more an internal thing inside the clock
>> controller.
>>
>> At least naming and perceived functionality would suggest a chain of
>>     hclk_vio -> hclk_vio_h2p -> pclk_mipi
> I personally wouldn't give to much on naming when it comes to Rockchip
> CRUs. Actually looking at "Fig. 2-5 Chip Clock Architecture Diagram 4" of
> RK312x its:
>
>
> ... -> hclk_vio
>
>                    -> hclk_h2p (clock in question)
>                    -> pclk_mipi (DSI APB clock)
>                    -> hclk_rga
>                    -> hclk_vop
>                    ....
>
> Also there is no other display output path (HDMI, LVDS) which requires 
> this
> clock to be enabled. They all work when it's disabled. That really 
> makes me
> think it's just the AHB clock line for the DSI controller. Maybe Andy can
> share some details?

Anyway: I just looked at the "MIPI Controller architecture" part of the 
TRM - there is not even AHB clock line, only APB. So I revert the change 
with the additional clock, make the h2p-clock critical again and resend.

Alex

>> In any case, I really don't see hclk_vio_h2p to be in the realm of the
>> actual DSI controller, but more a part of clock-controller / 
>> interconnect.
>> Similar to the NIU clocks for the interconnect.
>>
>> rk3588 actually tries to implement this already and while the
>> gate-link clocks are described as "recent", I think this definitly 
>> the same
>> concept used a most/all older Rockchip SoCs, just nobody cared about 
>> that
>> till now ;-) [0] .
>>
>> So TL;DR I'd really prefer to not leak CRU-details into the DSI 
>> controller.
>>
>>
>> Heiko
>>
>> [0] Which reminds me that I should look at Sebastian's make GATE-LINK
>> actually-work-patch.
>>
>>
>>
>>