linux-kernel - RE: [PATCH v2 2/8] dt-bindings: media: nxp: Add Wave6 video codec device

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Message-ID:
 <SL2P216MB124663E8210291761226DAC2FB9FA@SL2P216MB1246.KORP216.PROD.OUTLOOK.COM>
Date: Tue, 20 May 2025 08:31:19 +0000
From: Nas Chung <nas.chung@...psnmedia.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
CC: "mchehab@...nel.org" <mchehab@...nel.org>, "hverkuil@...all.nl"
	<hverkuil@...all.nl>, "robh@...nel.org" <robh@...nel.org>,
	"krzk+dt@...nel.org" <krzk+dt@...nel.org>, "conor+dt@...nel.org"
	<conor+dt@...nel.org>, "linux-media@...r.kernel.org"
	<linux-media@...r.kernel.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-imx@....com" <linux-imx@....com>,
	"marex@...x.de" <marex@...x.de>, jackson.lee <jackson.lee@...psnmedia.com>,
	lafley.kim <lafley.kim@...psnmedia.com>
Subject: RE: [PATCH v2 2/8] dt-bindings: media: nxp: Add Wave6 video codec
 device

Hi, Krzysztof.

>-----Original Message-----
>From: Krzysztof Kozlowski <krzk@...nel.org>
>Sent: Tuesday, May 20, 2025 3:27 PM
>To: Nas Chung <nas.chung@...psnmedia.com>
>Cc: mchehab@...nel.org; hverkuil@...all.nl; robh@...nel.org;
>krzk+dt@...nel.org; conor+dt@...nel.org; linux-media@...r.kernel.org;
>devicetree@...r.kernel.org; linux-kernel@...r.kernel.org; linux-imx@....com;
>marex@...x.de; jackson.lee <jackson.lee@...psnmedia.com>; lafley.kim
><lafley.kim@...psnmedia.com>
>Subject: Re: [PATCH v2 2/8] dt-bindings: media: nxp: Add Wave6 video codec
>device
>
>On 19/05/2025 07:08, Nas Chung wrote:
>> Hi, Krzysztof.
>>
>>> -----Original Message-----
>>> From: Krzysztof Kozlowski <krzk@...nel.org>
>>> Sent: Friday, May 16, 2025 9:56 PM
>>> To: Nas Chung <nas.chung@...psnmedia.com>
>>> Cc: mchehab@...nel.org; hverkuil@...all.nl;
>sebastian.fricke@...labora.com;
>>> robh@...nel.org; krzk+dt@...nel.org; conor+dt@...nel.org; linux-
>>> media@...r.kernel.org; devicetree@...r.kernel.org; linux-
>>> kernel@...r.kernel.org; linux-imx@....com; marex@...x.de; jackson.lee
>>> <jackson.lee@...psnmedia.com>; lafley.kim <lafley.kim@...psnmedia.com>
>>> Subject: Re: [PATCH v2 2/8] dt-bindings: media: nxp: Add Wave6 video
>codec
>>> device
>>>
>>> On 13/05/2025 09:39, Nas Chung wrote:
>>>>>
>>>>> All of above are wrong for the SoC...
>>>>>
>>>>>>
>>>>>>         #include <dt-bindings/interrupt-controller/arm-gic.h>
>>>>>>         #include <dt-bindings/clock/nxp,imx95-clock.h>
>>>>>>
>>>>>>         soc {
>>>>>>           #address-cells = <2>;
>>>>>>           #size-cells = <2>;
>>>>>>
>>>>>>           vpu: video-codec {
>>>>>>             compatible = "nxp,imx95-vpu", "cnm,wave633c";
>>>>>
>>>>> What does this device represent? It is not "ctrl", because you made
>ctrl
>>>>> separate device node. Your binding description suggests that is the
>VPU
>>>>> control region.
>>>>
>>>> My intention was to represent the MMIO VPU device, which includes
>>>> both the core and control nodes.
>>>
>>> Then what is the VPU device if not CTRL? What is the CTRL device?
>>
>> The VPU device represents the entire VPU hardware block,
>> which includes 1 CTRL component(node) and 4 CORE components(nodes).
>
>What is entire VPU hardware block?

I understand your point. The entire VPU hardware block cannot be considered
a device on its own.

>
>>
>> The CTRL device represents the VCPU, a 32-bit processor embedded within
>the
>> VPU hardware block. This VCPU is responsible for executing the VPU
>firmware.
>> The CTRL device is in charge of tasks such as firmware booting, power
>management
>> (sleep and wakeup command), and managing memory regions that are
>exclusively
>> accessed by the firmware.
>
>This sounds like CTRL is responsible for entire VPU block. What are the
>tasks of VPU block then? What are its registers? What is that device
>exactly doing?

You're right - the VPU block itself does not have any dedicated registers
or functionality beyond what is handled by the CTRL and CORE components.
Therefore, it cannot be clearly defined as a device.

>
>You keep repeating the same, so my initial idea - CTRL is not a separate
>block - still stands. Can you have more CTRL blocks than one?

No, there is only one CTRL block in the hardware.

I agree with your view that the CTRL node should be treated as the top-level
device node, with the COREs as its child nodes.
I will revise the bindings accordingly and reflect this structure in v3.

Thank you for the detailed feedback and clarification.

Thanks.
Nas.

>
>Best regards,
>Krzysztof