linux-kernel - Re: [PATCH 5/8] media: iris: Move vpu register defines to common header file

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Message-ID: <96aca644-8fdc-8076-c94b-ed655ac526d2@quicinc.com>
Date: Mon, 29 Sep 2025 11:14:53 +0530
From: Vishnu Reddy <quic_bvisredd@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Vikash Garodia
	<vikash.garodia@....qualcomm.com>,
        Dikshita Agarwal
	<dikshita.agarwal@....qualcomm.com>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Bryan O'Donoghue <bod@...nel.org>,
        Mauro Carvalho Chehab
	<mchehab@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski
	<krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Philipp Zabel
	<p.zabel@...gutronix.de>
CC: <linux-arm-msm@...r.kernel.org>, <linux-media@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/8] media: iris: Move vpu register defines to common
 header file



On 9/25/2025 2:40 PM, Konrad Dybcio wrote:
> On 9/25/25 1:14 AM, Vikash Garodia wrote:
>> Some of vpu4 register defines are common with vpu3x. Move those into the
>> common register defines header. This is done to reuse the defines for
>> vpu4 in subsequent patch which enables the power sequence for vpu4.
>>
>> Co-developed-by: Vishnu Reddy <quic_bvisredd@...cinc.com>
>> Signed-off-by: Vishnu Reddy <quic_bvisredd@...cinc.com>
>> Signed-off-by: Vikash Garodia <vikash.garodia@....qualcomm.com>
>> ---
>>   drivers/media/platform/qcom/iris/iris_vpu3x.c      | 36 ----------------------
>>   drivers/media/platform/qcom/iris/iris_vpu_common.c | 23 --------------
>>   .../platform/qcom/iris/iris_vpu_register_defines.h | 29 +++++++++++++++++
> 
> This is a slippery slope. I think it's better if you explicitly say
> the header file contains the register map of VPU3 instead, as let's say
> VPU5 may add a random register in the middle (pushing some existing ones
> +0x4 down). Such changes are annoying to debug, and we've unfortunately
> been there on Adreno..
> 
> Because you're using this for a single common function that is both acting
> upon the same registers and performing the same operations on them across
> VPU35 and VPU4, it's okay to de-static-ize the function from iris_vpu3.c and
> refer to it from vpu4 ops, keeping the register map private to the former
> file which I think will end up less error-prone for the future.
> 
> Konrad

  Just to confirm
  1. You’re saying it’s better to keep the register definitions for each
  VPU generation in their own source files, instead of keeping them all
  in a shared header. Is that right?

  2. The vpu functions (power on controller, power off controller and
  etc.) which are common for vpu3x and vpu4x are moved to
  iris_vpu_common.c and de-static-ize to use for both vpu3x and vpu4x.
  (This code changes are there in [PATCH 6/8] media: iris: Move vpu35
  specific api to common to use for vpu4)

  Will this 2nd point is fine or Do I need the keep the functions also
  in the platform specific file and reuse for vpu4x by de-static-ize the
  function in iris_vpu3x.c?

  Thanks and regards,
  Vishnu Reddy