[PATCH v6 4/6] hwmon: (fam15h_power) Introduce a cpu accumulated power reporting algorithm

[Huang Rui <ray.huang@amd.com>]

This patch introduces an algorithm that computes the average power by
reading a delta value of “core power accumulator” register during
measurement interval, and then dividing delta value by the length of
the time interval.

User is able to use power1_average entry to measure the processor power
consumption and power1_average_interval entry to set the interval.

A simple example:

ray@hr-ub:~/tip$ sensors
fam15h_power-pci-00c4
Adapter: PCI adapter
power1:       19.58 mW (avg =   2.55 mW, interval =   0.01 s)
                       (crit =  15.00 W)

...

The result is current average processor power consumption in 10
millisecond. The unit of the result is uWatt.

Suggested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Cc: Borislav Petkov <bp@alien8.de>
---
 drivers/hwmon/fam15h_power.c | 128 +++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 124 insertions(+), 4 deletions(-)

diff --git a/drivers/hwmon/fam15h_power.c b/drivers/hwmon/fam15h_power.c
index 336d422..5abbfa8 100644
--- a/drivers/hwmon/fam15h_power.c
+++ b/drivers/hwmon/fam15h_power.c
@@ -27,6 +27,8 @@
 #include <linux/bitops.h>
 #include <linux/cpu.h>
 #include <linux/cpumask.h>
+#include <linux/time.h>
+#include <linux/sched.h>
 #include <asm/processor.h>
 #include <asm/msr.h>
 
@@ -48,6 +50,9 @@ MODULE_LICENSE("GPL");
 #define FAM15H_NUM_GROUPS		2
 #define MAX_CUS				8
 
+/* set maximum interval as 1 second */
+#define MAX_INTERVAL			1000
+
 #define MSR_F15H_CU_PWR_ACCUMULATOR	0xc001007a
 #define MSR_F15H_CU_MAX_PWR_ACCUMULATOR	0xc001007b
 #define MSR_F15H_PTSC			0xc0010280
@@ -68,6 +73,9 @@ struct fam15h_power_data {
 	u64 cu_acc_power[MAX_CUS];
 	/* performance timestamp counter */
 	u64 cpu_sw_pwr_ptsc[MAX_CUS];
+	/* online/offline status of current compute unit */
+	int cu_on[MAX_CUS];
+	unsigned long power_period;
 };
 
 static ssize_t show_power(struct device *dev,
@@ -149,6 +157,8 @@ static void do_read_registers_on_cu(void *_data)
 
 	rdmsrl_safe(MSR_F15H_CU_PWR_ACCUMULATOR, &data->cu_acc_power[cu]);
 	rdmsrl_safe(MSR_F15H_PTSC, &data->cpu_sw_pwr_ptsc[cu]);
+
+	data->cu_on[cu] = 1;
 }
 
 /*
@@ -165,6 +175,8 @@ static int read_registers(struct fam15h_power_data *data)
 	if (!ret)
 		return -ENOMEM;
 
+	memset(data->cu_on, 0, sizeof(int) * MAX_CUS);
+
 	get_online_cpus();
 	this_cpu = smp_processor_id();
 
@@ -199,6 +211,98 @@ static int read_registers(struct fam15h_power_data *data)
 	return 0;
 }
 
+static ssize_t acc_show_power(struct device *dev,
+			      struct device_attribute *attr,
+			      char *buf)
+{
+	struct fam15h_power_data *data = dev_get_drvdata(dev);
+	u64 prev_cu_acc_power[MAX_CUS], prev_ptsc[MAX_CUS],
+	    jdelta[MAX_CUS];
+	u64 tdelta, avg_acc;
+	int cu, cu_num, ret;
+	signed long leftover;
+
+	/*
+	 * With the new x86 topology modelling, x86_max_cores is the
+	 * compute unit number.
+	 */
+	cu_num = boot_cpu_data.x86_max_cores;
+
+	ret = read_registers(data);
+	if (ret)
+		return 0;
+
+	for (cu = 0; cu < cu_num; cu++) {
+		prev_cu_acc_power[cu] = data->cu_acc_power[cu];
+		prev_ptsc[cu] = data->cpu_sw_pwr_ptsc[cu];
+	}
+
+	leftover = schedule_timeout_interruptible(msecs_to_jiffies(data->power_period));
+	if (leftover)
+		return 0;
+
+	ret = read_registers(data);
+	if (ret)
+		return 0;
+
+	for (cu = 0, avg_acc = 0; cu < cu_num; cu++) {
+		/* check if current compute unit is online */
+		if (data->cu_on[cu] == 0)
+			continue;
+
+		if (data->cu_acc_power[cu] < prev_cu_acc_power[cu]) {
+			jdelta[cu] = data->max_cu_acc_power + data->cu_acc_power[cu];
+			jdelta[cu] -= prev_cu_acc_power[cu];
+		} else {
+			jdelta[cu] = data->cu_acc_power[cu] - prev_cu_acc_power[cu];
+		}
+		tdelta = data->cpu_sw_pwr_ptsc[cu] - prev_ptsc[cu];
+		jdelta[cu] *= data->cpu_pwr_sample_ratio * 1000;
+		do_div(jdelta[cu], tdelta);
+
+		/* the unit is microWatt */
+		avg_acc += jdelta[cu];
+	}
+
+	return sprintf(buf, "%llu\n", (unsigned long long)avg_acc);
+}
+static DEVICE_ATTR(power1_average, S_IRUGO, acc_show_power, NULL);
+
+static ssize_t acc_show_power_period(struct device *dev,
+				     struct device_attribute *attr,
+				     char *buf)
+{
+	struct fam15h_power_data *data = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%lu\n", data->power_period);
+}
+
+static ssize_t acc_set_power_period(struct device *dev,
+				    struct device_attribute *attr,
+				    const char *buf, size_t count)
+{
+	struct fam15h_power_data *data = dev_get_drvdata(dev);
+	unsigned long temp;
+	int ret;
+
+	ret = kstrtoul(buf, 10, &temp);
+	if (ret)
+		return ret;
+
+	if (temp > MAX_INTERVAL)
+		return -EINVAL;
+
+	/* the interval value should be greater than 0 */
+	if (temp <= 0)
+		return -EINVAL;
+
+	data->power_period = temp;
+
+	return count;
+}
+static DEVICE_ATTR(power1_average_interval, S_IRUGO | S_IWUSR,
+		   acc_show_power_period, acc_set_power_period);
+
 static int fam15h_power_init_attrs(struct pci_dev *pdev,
 				   struct fam15h_power_data *data)
 {
@@ -211,6 +315,10 @@ static int fam15h_power_init_attrs(struct pci_dev *pdev,
 	     (c->x86_model >= 0x60 && c->x86_model <= 0x7f)))
 		n += 1;
 
+	/* check if processor supports accumulated power */
+	if (boot_cpu_has(X86_FEATURE_ACC_POWER))
+		n += 2;
+
 	fam15h_power_attrs = devm_kcalloc(&pdev->dev, n,
 					  sizeof(*fam15h_power_attrs),
 					  GFP_KERNEL);
@@ -225,6 +333,11 @@ static int fam15h_power_init_attrs(struct pci_dev *pdev,
 	     (c->x86_model >= 0x60 && c->x86_model <= 0x7f)))
 		fam15h_power_attrs[n++] = &dev_attr_power1_input.attr;
 
+	if (boot_cpu_has(X86_FEATURE_ACC_POWER)) {
+		fam15h_power_attrs[n++] = &dev_attr_power1_average.attr;
+		fam15h_power_attrs[n++] = &dev_attr_power1_average_interval.attr;
+	}
+
 	data->group.attrs = fam15h_power_attrs;
 
 	return 0;
@@ -290,7 +403,7 @@ static int fam15h_power_resume(struct pci_dev *pdev)
 static int fam15h_power_init_data(struct pci_dev *f4,
 				  struct fam15h_power_data *data)
 {
-	u32 val, eax, ebx, ecx, edx;
+	u32 val;
 	u64 tmp;
 	int ret;
 
@@ -317,10 +430,9 @@ static int fam15h_power_init_data(struct pci_dev *f4,
 	if (ret)
 		return ret;
 
-	cpuid(0x80000007, &eax, &ebx, &ecx, &edx);
 
 	/* CPUID Fn8000_0007:EDX[12] indicates to support accumulated power */
-	if (!(edx & BIT(12)))
+	if (!boot_cpu_has(X86_FEATURE_ACC_POWER))
 		return 0;
 
 	/*
@@ -328,7 +440,7 @@ static int fam15h_power_init_data(struct pci_dev *f4,
 	 * sample period to the PTSC counter period by executing CPUID
 	 * Fn8000_0007:ECX
 	 */
-	data->cpu_pwr_sample_ratio = ecx;
+	data->cpu_pwr_sample_ratio = cpuid_ecx(0x80000007);
 
 	if (rdmsrl_safe(MSR_F15H_CU_MAX_PWR_ACCUMULATOR, &tmp)) {
 		pr_err("Failed to read max compute unit power accumulator MSR\n");
@@ -337,6 +449,14 @@ static int fam15h_power_init_data(struct pci_dev *f4,
 
 	data->max_cu_acc_power = tmp;
 
+	/*
+	 * Milliseconds are a reasonable interval for the measurement.
+	 * But it shouldn't set too long here, because several seconds
+	 * would cause the read function to hang. So set default
+	 * interval as 10 ms.
+	 */
+	data->power_period = 10;
+
 	return read_registers(data);
 }
 
-- 
1.9.1