linux-kernel - Re: [PATCH v5 2/2] cpufreq: qcom-hw: Add support for QCOM cpufreq HW driver

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Date:   Mon, 16 Jul 2018 16:02:33 -0700
From:   Evan Green <evgreen@...gle.com>
To:     tdas@...eaurora.org
Cc:     rjw@...ysocki.net, viresh.kumar@...aro.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        sboyd@...nel.org, Rajendra Nayak <rnayak@...eaurora.org>,
        anischal@...eaurora.org, devicetree@...r.kernel.org,
        robh@...nel.org, Saravana Kannan <skannan@...eaurora.org>,
        amit.kucheria@...aro.org
Subject: Re: [PATCH v5 2/2] cpufreq: qcom-hw: Add support for QCOM cpufreq HW driver

Hi Taniya,
On Thu, Jul 12, 2018 at 11:06 AM Taniya Das <tdas@...eaurora.org> wrote:
>
> The CPUfreq HW present in some QCOM chipsets offloads the steps necessary
> for changing the frequency of CPUs. The driver implements the cpufreq
> driver interface for this hardware engine.
>
> Signed-off-by: Saravana Kannan <skannan@...eaurora.org>
> Signed-off-by: Taniya Das <tdas@...eaurora.org>
> ---
>  drivers/cpufreq/Kconfig.arm       |  10 ++
>  drivers/cpufreq/Makefile          |   1 +
>  drivers/cpufreq/qcom-cpufreq-hw.c | 344 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 355 insertions(+)
>  create mode 100644 drivers/cpufreq/qcom-cpufreq-hw.c
>
...
> diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
> new file mode 100644
> index 0000000..fa25a95
> --- /dev/null
> +++ b/drivers/cpufreq/qcom-cpufreq-hw.c
...
> +static int qcom_cpufreq_hw_cpu_init(struct cpufreq_policy *policy)
> +{
> +       struct cpufreq_qcom *c;
> +
> +       c = qcom_freq_domain_map[policy->cpu];
> +       if (!c) {
> +               pr_err("No scaling support for CPU%d\n", policy->cpu);
> +               return -ENODEV;
> +       }
> +
> +       cpumask_copy(policy->cpus, &c->related_cpus);
> +
> +       policy->fast_switch_possible = true;
> +       policy->freq_table = c->table;
> +       policy->driver_data = c;
> +
> +       return 0;
I haven't looked at this driver in detail, but I have tested it.
Instead of the line above, I needed:

return cpufreq_table_validate_and_show(policy, c->table);

Without this the framework thinks that the min and max frequencies are
zero, and then you get a warning about an invalid table. I also
removed "policy->freq_table = c->table", since validate_and_show does
this.
-Evan