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

Lukasz Luba
2020-11-19T12:42:00Z

Hi Hector,

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