linux-kernel - Re: [PATCH v3 0/3] Use APIs in gdsc genpd to switch gdsc mode for venus v4 core

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Message-ID: <00449451-d97f-47fe-b0ab-cddb9d2b0e93@quicinc.com>
Date: Fri, 17 Jan 2025 12:17:21 +0800
From: Renjiang Han <quic_renjiang@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: Bjorn Andersson <andersson@...nel.org>,
        Michael Turquette
	<mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Stanimir Varbanov
	<stanimir.k.varbanov@...il.com>,
        Vikash Garodia <quic_vgarodia@...cinc.com>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Mauro Carvalho Chehab
	<mchehab@...nel.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>,
        Taniya Das <quic_tdas@...cinc.com>
Subject: Re: [PATCH v3 0/3] Use APIs in gdsc genpd to switch gdsc mode for
 venus v4 core


On 1/15/2025 5:59 PM, Dmitry Baryshkov wrote:
>> If only the clock patch or the venus driver patch is merged, the venus
>> driver will not work properly. Although it does not affect other system
>> functions, it is still recommended to wait until both the clock patch
>> and the venus driver patch are reviewed and passed, and then merge them
>> into the same release by their respective maintainers.
> NO! This will not work, as both -media and arm-soc branches will be
> broken. Please read about the git-bisect before making such suggestions.
>
> A proper plan would be:
> - implement a function which allows one to check that hwmode is
>    supported by the genpd driver
> - Change Venus to use hwmode for those platforms if it is enabled
> - Enable HWMODE support in the clock driver. Clearly identify that this
>    patch should be merged together and after Venus changes if all
>    maintainers agree with that
> - Clean up now-dead code.
>
> Doing it in any other way would result in the broken kernels.
  Thanks for your comment. dev_pm_genpd_set_hwmode() has a check function.
  So I think I can do it like this to add compatibility in venus driver:
  - 1. the dev_pm_genpd_set_hwmode() is used to switch the GDSC mode by
  default.
  - 2. If it fails and dev_pm_genpd_set_hwmode() returns -EOPNOTSUPP, it
  means that the clock driver uses the HW_CTRL flag. At this time, the
  GDSC mode is switched by writing the POWER_CONTROL register.

  In addition, the merged code needs to follow this order.
  - 1. Add compatibility in venus driver.
  - 2. Use the HW_CTRL_TRIGGER flag in clock driver
  - 3. Remove the dead code in venus driver.

-- 
Best Regards,
Renjiang