Date:   Mon, 12 Jul 2021 21:09:27 -0400
From:   Thara Gopinath <thara.gopinath@...aro.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     agross@...nel.org, rui.zhang@...el.com, daniel.lezcano@...aro.org,
        viresh.kumar@...aro.org, rjw@...ysocki.net, robh+dt@...nel.org,
        tdas@...eaurora.org, mka@...omium.org,
        linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [Patch v3 3/6] cpufreq: qcom-cpufreq-hw: Add dcvs interrupt
 support



On 7/10/21 12:57 AM, Bjorn Andersson wrote:
> On Thu 08 Jul 07:06 CDT 2021, Thara Gopinath wrote:
> 
>> Add interrupt support to notify the kernel of h/w initiated frequency
>> throttling by LMh. Convey this to scheduler via thermal presssure
>> interface.
>>
>> Signed-off-by: Thara Gopinath <thara.gopinath@...aro.org>
>> ---
>>
>> v2->v3:
>> 	- Cosmetic fixes from review comments on the list.
>> 	- Moved all LMh initializations to qcom_cpufreq_hw_lmh_init.
>> 	- Added freeing of LMh interrupt and cancelling the polling worker to
>> 	  qcom_cpufreq_hw_cpu_exit as per Viresh's suggestion.
>> 	- LMh interrupts are now tied to cpu dev and not cpufreq dev. This will be
>> 	  useful for further generation of SoCs where the same interrupt signals
>> 	  multiple cpu clusters.
>>
>> v1->v2:
>> 	- Introduced qcom_cpufreq_hw_lmh_init to consolidate LMh related initializations
>> 	  as per Viresh's review comment.
>> 	- Moved the piece of code restarting polling/re-enabling LMh interrupt to
>> 	  qcom_lmh_dcvs_notify therby simplifying isr and timer callback as per Viresh's
>> 	  suggestion.
>> 	- Droped cpus from qcom_cpufreq_data and instead using cpus from cpufreq_policy in
>> 	  qcom_lmh_dcvs_notify as per Viresh's review comment.
>> 	- Dropped dt property qcom,support-lmh as per Bjorn's suggestion.
>> 	- Other minor/cosmetic fixes
>>
>>   drivers/cpufreq/qcom-cpufreq-hw.c | 118 ++++++++++++++++++++++++++++++
>>   1 file changed, 118 insertions(+)
>>
>> diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
>> index f86859bf76f1..bb5fc700d913 100644
>> --- a/drivers/cpufreq/qcom-cpufreq-hw.c
>> +++ b/drivers/cpufreq/qcom-cpufreq-hw.c
>> @@ -7,6 +7,7 @@
>>   #include <linux/cpufreq.h>
>>   #include <linux/init.h>
>>   #include <linux/interconnect.h>
>> +#include <linux/interrupt.h>
>>   #include <linux/kernel.h>
>>   #include <linux/module.h>
>>   #include <linux/of_address.h>
>> @@ -22,10 +23,13 @@
>>   #define CLK_HW_DIV			2
>>   #define LUT_TURBO_IND			1
>>   
>> +#define HZ_PER_KHZ			1000
>> +
>>   struct qcom_cpufreq_soc_data {
>>   	u32 reg_enable;
>>   	u32 reg_freq_lut;
>>   	u32 reg_volt_lut;
>> +	u32 reg_current_vote;
>>   	u32 reg_perf_state;
>>   	u8 lut_row_size;
>>   };
>> @@ -33,7 +37,10 @@ struct qcom_cpufreq_soc_data {
>>   struct qcom_cpufreq_data {
>>   	void __iomem *base;
>>   	struct resource *res;
>> +	struct delayed_work lmh_dcvs_poll_work;
> 
> How about dropping "lmh" from this variable name?
> 
> Perhaps "throttle_work" or something like that?
> 
>>   	const struct qcom_cpufreq_soc_data *soc_data;
>> +	struct cpufreq_policy *policy;
>> +	int lmh_dcvs_irq;
> 
> throttle_irq ?

sounds good!

> 
>>   };
>>   
>>   static unsigned long cpu_hw_rate, xo_rate;
>> @@ -251,10 +258,84 @@ static void qcom_get_related_cpus(int index, struct cpumask *m)
>>   	}
>>   }
>>   
>> +static inline unsigned long qcom_lmh_vote_to_freq(u32 val)
>> +{
>> +	return (val & 0x3FF) * 19200;
>> +}
>> +
>> +static void qcom_lmh_dcvs_notify(struct qcom_cpufreq_data *data)
>> +{
>> +	struct cpufreq_policy *policy = data->policy;
>> +	struct dev_pm_opp *opp;
>> +	struct device *dev;
>> +	unsigned long max_capacity, capacity, freq_hz, throttled_freq;
>> +	unsigned int val, freq;
>> +
>> +	/*
>> +	 * Get the h/w throttled frequency, normalize it using the
>> +	 * registered opp table and use it to calculate thermal pressure.
>> +	 */
>> +	val = readl_relaxed(data->base + data->soc_data->reg_current_vote);
> 
> I would find it cleaner to move the readl() into the helper function, as
> you don't care about the register value, only the resulting frequency.

Ok..

> 
>> +	freq = qcom_lmh_vote_to_freq(val);
>> +	freq_hz = freq * HZ_PER_KHZ;
>> +
>> +	dev = get_cpu_device(cpumask_first(policy->cpus));
>> +	opp = dev_pm_opp_find_freq_floor(dev, &freq_hz);
>> +	if (IS_ERR(opp) && PTR_ERR(opp) == -ERANGE)
>> +		opp = dev_pm_opp_find_freq_ceil(dev, &freq_hz);
>> +
>> +	throttled_freq = freq_hz / HZ_PER_KHZ;
>> +
>> +	/* Update thermal pressure */
>> +
>> +	max_capacity = arch_scale_cpu_capacity(cpumask_first(policy->cpus));
>> +	capacity = throttled_freq * max_capacity;
>> +	capacity /= policy->cpuinfo.max_freq;
> 
> Perhaps, to avoid overflows if this is ever used on a 32-bit platform
> use:
> 
> 	mult_frac(max_capacity, throttled_freq, policy->cpuinfo.max_freq)

yep. sounds good.

> 
>> +
>> +	/* Don't pass boost capacity to scheduler */
>> +	if (capacity > max_capacity)
>> +		capacity = max_capacity;
>> +
>> +	arch_set_thermal_pressure(policy->cpus, max_capacity - capacity);
>> +
>> +	/*
>> +	 * If h/w throttled frequency is higher than what cpufreq has requested for, stop
>> +	 * polling and switch back to interrupt mechanism
>> +	 */
>> +
>> +	if (throttled_freq >= qcom_cpufreq_hw_get(cpumask_first(policy->cpus)))
>> +		/* Clear the existing interrupts and enable it back */
>> +		enable_irq(data->lmh_dcvs_irq);
>> +	else
>> +		mod_delayed_work(system_highpri_wq, &data->lmh_dcvs_poll_work,
>> +				 msecs_to_jiffies(10));
>> +}
>> +
>> +static void qcom_lmh_dcvs_poll(struct work_struct *work)
>> +{
>> +	struct qcom_cpufreq_data *data;
>> +
>> +	data = container_of(work, struct qcom_cpufreq_data, lmh_dcvs_poll_work.work);
>> +
>> +	qcom_lmh_dcvs_notify(data);
>> +}
>> +
>> +static irqreturn_t qcom_lmh_dcvs_handle_irq(int irq, void *data)
>> +{
>> +	struct qcom_cpufreq_data *c_data = data;
>> +
>> +	/* Disable interrupt and enable polling */
>> +	disable_irq_nosync(c_data->lmh_dcvs_irq);
>> +	qcom_lmh_dcvs_notify(c_data);
>> +
>> +	return 0;
>> +}
>> +
>>   static const struct qcom_cpufreq_soc_data qcom_soc_data = {
>>   	.reg_enable = 0x0,
>>   	.reg_freq_lut = 0x110,
>>   	.reg_volt_lut = 0x114,
>> +	.reg_current_vote = 0x704,
>>   	.reg_perf_state = 0x920,
>>   	.lut_row_size = 32,
>>   };
>> @@ -274,6 +355,35 @@ static const struct of_device_id qcom_cpufreq_hw_match[] = {
>>   };
>>   MODULE_DEVICE_TABLE(of, qcom_cpufreq_hw_match);
>>   
>> +static int qcom_cpufreq_hw_lmh_init(struct cpufreq_policy *policy, int index)
>> +{
>> +	struct qcom_cpufreq_data *data = policy->driver_data;
>> +	struct platform_device *pdev = cpufreq_get_driver_data();
>> +	struct device *cpu_dev = get_cpu_device(policy->cpu);
>> +	char irq_name[15];
>> +	int ret;
>> +
>> +	/*
>> +	 * Look for LMh interrupt. If no interrupt line is specified /
>> +	 * if there is an error, allow cpufreq to be enabled as usual.
>> +	 */
>> +	data->lmh_dcvs_irq = platform_get_irq(pdev, index);
>> +	if (data->lmh_dcvs_irq <= 0)
>> +		return data->lmh_dcvs_irq == -EPROBE_DEFER ? -EPROBE_DEFER : 0;
>> +
>> +	snprintf(irq_name, sizeof(irq_name), "dcvsh-irq-%u", policy->cpu);
>> +	ret = devm_request_irq(cpu_dev, data->lmh_dcvs_irq, qcom_lmh_dcvs_handle_irq,
>> +			       0, irq_name, data);
>> +	if (ret) {
>> +		dev_err(&pdev->dev, "Error %d registering irq %x\n", ret, data->lmh_dcvs_irq);
> 
> The irq number here won't have any meaning, and %x wouldn't be suitable.
> 
> How about ..."Error registering %s: %d\n", irq_name, ret); ?

ok.

> 
>> +		return 0;
> 
> This sounds like a problem, wouldn't it be suitable to treat it as a
> problem?

I thought a lot about this. My point is even if LMh does not get enabled 
due to some reason, cpufreq should be enabled. If I return an error back 
from here, cpufreq will be disabled.


> 
>> +	}
>> +	data->policy = policy;
> 
> Afaict, no one is going to access data->policy unless devm_request_irq()
> succeeds and if it does and the interrupt fires immediately it would be
> too late to set it here. So better move it earlier.
> 
>> +	INIT_DEFERRABLE_WORK(&data->lmh_dcvs_poll_work, qcom_lmh_dcvs_poll);
> 
> What if the interrupt fires before you initialize the work? Better move
> this higher up.

I will move this and the data->policy = policy above before requesting 
the interrupt.

> 
>> +
>> +	return 0;
>> +}
>> +
>>   static int qcom_cpufreq_hw_cpu_init(struct cpufreq_policy *policy)
>>   {
>>   	struct platform_device *pdev = cpufreq_get_driver_data();
>> @@ -370,6 +480,10 @@ static int qcom_cpufreq_hw_cpu_init(struct cpufreq_policy *policy)
>>   			dev_warn(cpu_dev, "failed to enable boost: %d\n", ret);
>>   	}
>>   
>> +	ret = qcom_cpufreq_hw_lmh_init(policy, index);
>> +	if (ret)
>> +		goto error;
>> +
>>   	return 0;
>>   error:
>>   	kfree(data);
>> @@ -389,6 +503,10 @@ static int qcom_cpufreq_hw_cpu_exit(struct cpufreq_policy *policy)
>>   
>>   	dev_pm_opp_remove_all_dynamic(cpu_dev);
>>   	dev_pm_opp_of_cpumask_remove_table(policy->related_cpus);
>> +	if (data->lmh_dcvs_irq > 0) {
>> +		devm_free_irq(cpu_dev, data->lmh_dcvs_irq, data);
> 
> As init/exit are called multiple times you should avoid the devm
> variants.

Yes. I think Viresh was also mentioning this. I will move to non devm 
version.

> 
> Regards,
> Bjorn
> 
>> +		cancel_delayed_work_sync(&data->lmh_dcvs_poll_work);
>> +	}
>>   	kfree(policy->freq_table);
>>   	kfree(data);
>>   	iounmap(base);
>> -- 
>> 2.25.1
>>

-- 
Warm Regards
Thara (She/Her/Hers)

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