linux-kernel - Re: [PATCH v4 3/4] dt-bindings: display: rockchip: Add schema for RK3588 HDMI TX Controller

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Message-ID: <2085e998-a453-4893-9e80-3be68b0fb13d@collabora.com>
Date: Thu, 22 Aug 2024 02:22:16 +0300
From: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
To: Heiko Stuebner <heiko@...ech.de>, Conor Dooley <conor@...nel.org>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>,
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>,
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 Sandy Huang <hjc@...k-chips.com>, Andy Yan <andy.yan@...k-chips.com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Mark Yao <markyao0591@...il.com>,
 Sascha Hauer <s.hauer@...gutronix.de>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org, devicetree@...r.kernel.org,
 kernel@...labora.com, Alexandre ARNOUD <aarnoud@...com>,
 Luis de Arquer <ldearquer@...il.com>
Subject: Re: [PATCH v4 3/4] dt-bindings: display: rockchip: Add schema for
 RK3588 HDMI TX Controller

On 8/22/24 12:38 AM, Heiko Stuebner wrote:
> 
> 
> Am 21. August 2024 23:28:55 MESZ schrieb Conor Dooley <conor@...nel.org>:
>> Cristian, Heiko,
>>
>> On Wed, Aug 21, 2024 at 11:38:01PM +0300, Cristian Ciocaltea wrote:
>>> On 8/21/24 6:07 PM, Conor Dooley wrote:
>>>> On Tue, Aug 20, 2024 at 11:12:45PM +0300, Cristian Ciocaltea wrote:
>>>>> On 8/20/24 7:14 PM, Conor Dooley wrote:
>>>>>> On Tue, Aug 20, 2024 at 03:37:44PM +0300, Cristian Ciocaltea wrote:
>>>>>>> On 8/19/24 7:53 PM, Conor Dooley wrote:
>>>>>>>> On Mon, Aug 19, 2024 at 01:29:30AM +0300, Cristian Ciocaltea wrote:
>>>>>>>>> +  rockchip,grf:
>>>>>>>>> +    $ref: /schemas/types.yaml#/definitions/phandle
>>>>>>>>> +    description:
>>>>>>>>> +      Most HDMI QP related data is accessed through SYS GRF regs.
>>>>>>>>> +
>>>>>>>>> +  rockchip,vo1-grf:
>>>>>>>>> +    $ref: /schemas/types.yaml#/definitions/phandle
>>>>>>>>> +    description:
>>>>>>>>> +      Additional HDMI QP related data is accessed through VO1 GRF regs.
>>>>>>>>
>>>>>>>> Why are these required? What prevents you looking up the syscons by
>>>>>>>> compatible?
>>>>>>>
>>>>>>> That is for getting the proper instance:
>>>>>>
>>>>>> Ah, that makes sense. I am, however, curious why these have the same
>>>>>> compatible when they have different sized regions allocated to them.
>>>>>
>>>>> Good question, didn't notice.  I've just checked the TRM and, in both
>>>>> cases, the maximum register offset is within the 0x100 range.  Presumably
>>>>> this is nothing but an inconsistency, as the syscons have been added in
>>>>> separate commits.
>>>>
>>>> Is that TRM publicly available? I do find it curious that devices sound
>>>> like they have different contents have the same compatible. In my view,
>>>> that is incorrect and they should have unique compatibles if the
>>>> contents (and therefore the programming model) differs.
>>>
>>> Don't know if there's an official location to get it from, but a quick
>>> search on internet shows a few repos providing them, e.g. [1].
>>>
>>> Comparing "6.14 VO0_GRF Register Description" at pg. 777 with "6.15 VO1_GRF
>>> Register Description" at pg. 786 (from Part1) reveals the layout is mostly
>>> similar, with a few variations though.
>>
>> Page references and everything, thank you very much. I don't think those
>> two GRFs should have the same compatibles, they're, as you say, similar
>> but not identical. Seems like a bug to me!
>>
>> Heiko, what do you think?
> 
> Yes, while the register names sound similar, looking at the bit
> definitions this evening revealed that they handle vastly different
> settings.
> 
> So I guess we should fix the compatibles. They are all about graphics
> stuff and HDMI actually is the first output, so right now WE can at least
> still claim the no-users joker ;-)

I couldn't find any driver doing a lookup for them by compatible, so I
think it's fine to fix them - should we go for "rockchip,rk3588-vo0-grf" and
"rockchip,rk3588-vo1-grf", respectively?

vo0_grf seems to be used by the usbdp phy nodes:

    usbdp_phy0: phy@...80000 {
        compatible = "rockchip,rk3588-usbdp-phy";
        [...]
        rockchip,vo-grf = <&vo0_grf>;
        [...]

Same for "usbdp_phy1: phy@...90000".

While vo1_grf is present in:

    vop: vop@...90000 {
        compatible = "rockchip,rk3588-vop";
        [...]
        rockchip,vo1-grf = <&vo1_grf>;
        [...]

I guess it's too late to drop them while updating the related drivers
accordingly, hence I wonder if we should keep using the phandles for this
HDMI thing as well, for consistency reasons.

Thanks,
Cristian

> Heiko
> 
>>
>>> [1] https://github.com/FanX-Tek/rk3588-TRM-and-Datasheet
>>>
>>>>>
>>>>>>> 	vo0_grf: syscon@...a6000 {
>>>>>>> 		compatible = "rockchip,rk3588-vo-grf", "syscon";
>>>>>>> 		reg = <0x0 0xfd5a6000 0x0 0x2000>;
>>>>>>> 		clocks = <&cru PCLK_VO0GRF>;
>>>>>>> 	};
>>>>>>>
>>>>>>> 	vo1_grf: syscon@...a8000 {
>>>>>>> 		compatible = "rockchip,rk3588-vo-grf", "syscon";
>>>>>>> 		reg = <0x0 0xfd5a8000 0x0 0x100>;
>>>>>>> 		clocks = <&cru PCLK_VO1GRF>;
>>>>>>> 	};
>>>>
>