linux-kernel - Re: [TEGRA194_CPUFREQ Patch 2/3] cpufreq: Add Tegra194 cpufreq driver

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Message-ID: <20191204054043.o4ff7pnqec3fwdgu@vireshk-i7>
Date:   Wed, 4 Dec 2019 11:10:43 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Sumit Gupta <sumitg@...dia.com>
Cc:     rjw@...ysocki.net, catalin.marinas@....com, will@...nel.org,
        thierry.reding@...il.com, jonathanh@...dia.com, talho@...dia.com,
        linux-pm@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        bbasu@...dia.com, mperttunen@...dia.com
Subject: Re: [TEGRA194_CPUFREQ Patch 2/3] cpufreq: Add Tegra194 cpufreq driver

Hi Sumit,

On 03-12-19, 23:02, Sumit Gupta wrote:
> Add support for CPU frequency scaling on Tegra194. The frequency
> of each core can be adjusted by writing a clock divisor value to
> an MSR on the core. The range of valid divisors is queried from
> the BPMP.
> 
> Signed-off-by: Mikko Perttunen <mperttunen@...dia.com>
> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
> ---
>  drivers/cpufreq/Kconfig.arm        |   6 +
>  drivers/cpufreq/Makefile           |   1 +
>  drivers/cpufreq/tegra194-cpufreq.c | 423 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 430 insertions(+)
>  create mode 100644 drivers/cpufreq/tegra194-cpufreq.c

Overall these are the things that you are doing here in the driver:

- open coded clk_{get|set}_rate(), why can't you implement a clock
  driver for the CPU and use the clk framework? You may not need the
  (hacky) work-queue usage then probably.

- populating cpufreq table, you can probably add OPPs instead using
  the same mechanism

- And then you can reuse the cpufreq-dt driver for your platform as
  well, as is the case for few other tegra platforms.

-- 
viresh