linux-kernel - Re: [PATCH v8 1/3] cpufreq: mediatek-hw: Add support for CPUFREQ HW

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Date:   Thu, 19 Nov 2020 12:41:38 +0000
From:   Lukasz Luba <lukasz.luba@....com>
To:     Hector Yuan <hector.yuan@...iatek.com>
Cc:     linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Maxime Ripard <mripard@...nel.org>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Amit Kucheria <amit.kucheria@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Dave Gerlach <d-gerlach@...com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Robin Murphy <robin.murphy@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        wsd_upstream@...iatek.com
Subject: Re: [PATCH v8 1/3] cpufreq: mediatek-hw: Add support for CPUFREQ HW

Hi Hector,

On 10/26/20 8:19 AM, Hector Yuan wrote:
> From: "Hector.Yuan" <hector.yuan@...iatek.com>
> 
> Add cpufreq HW support.
> 
> Signed-off-by: Hector.Yuan <hector.yuan@...iatek.com>

[snip]

> +
> +static int mtk_cpufreq_hw_cpu_init(struct cpufreq_policy *policy)
> +{
> +	struct cpufreq_mtk *c;
> +	struct device *cpu_dev;
> +	struct em_data_callback em_cb = EM_DATA_CB(mtk_cpufreq_get_cpu_power);
> +	struct pm_qos_request *qos_request;
> +	int sig, pwr_hw = CPUFREQ_HW_STATUS | SVS_HW_STATUS;
> +
> +	qos_request = kzalloc(sizeof(*qos_request), GFP_KERNEL);
> +	if (!qos_request)
> +		return -ENOMEM;
> +
> +	cpu_dev = get_cpu_device(policy->cpu);
> +	if (!cpu_dev) {
> +		pr_err("failed to get cpu%d device\n", policy->cpu);
> +		return -ENODEV;
> +	}
> +
> +	c = mtk_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->freq_table = c->table;
> +	policy->driver_data = c;

To control frequency transition rate in schedutil, you might
be interested in setting:

policy->cpuinfo.transition_latency = <mtk_value_here>;

Example, when this latency value comes from FW [1]

> +
> +	/* Let CPUs leave idle-off state for SVS CPU initializing */
> +	cpu_latency_qos_add_request(qos_request, 0);
> +
> +	/* HW should be in enabled state to proceed now */
> +	writel_relaxed(0x1, c->reg_bases[REG_FREQ_ENABLE]);
> +
> +	if (readl_poll_timeout(c->reg_bases[REG_FREQ_HW_STATE], sig,
> +			       (sig & pwr_hw) == pwr_hw, POLL_USEC,
> +			       TIMEOUT_USEC)) {
> +		if (!(sig & CPUFREQ_HW_STATUS)) {
> +			pr_info("cpufreq hardware of CPU%d is not enabled\n",
> +				policy->cpu);
> +			return -ENODEV;
> +		}
> +
> +		pr_info("SVS of CPU%d is not enabled\n", policy->cpu);
> +	}
> +
> +	em_dev_register_perf_domain(cpu_dev, c->nr_opp, &em_cb, policy->cpus);

Please keep in mind that this is going to be changed soon with a new
argument: 'milliwatts'. It's queued in pm/linux-next [2].

Regards,
Lukasz

[1] 
https://elixir.bootlin.com/linux/latest/source/drivers/cpufreq/scmi-cpufreq.c#L194
[2] 
https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git/commit/?h=linux-next&id=c250d50fe2ce627ca9805d9c8ac11cbbf922a4a6