Re: [PATCH v1] cpufreq: qcom: Read voltage LUT and populate OPP

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Hello Matthias,

Thanks for your review comments.

On 12/22/2018 2:27 AM, Matthias Kaehlcke wrote:
Hi Taniya,

On Fri, Dec 21, 2018 at 11:36:48PM +0530, Taniya Das wrote:
Add support to read the voltage look up table and populate OPP for all
corresponding CPUS.

Signed-off-by: Taniya Das <tdas@xxxxxxxxxxxxxx>
---
  drivers/cpufreq/qcom-cpufreq-hw.c | 32 ++++++++++++++++++++++++++++++--
  1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
index d83939a..7559b87 100644
--- a/drivers/cpufreq/qcom-cpufreq-hw.c
+++ b/drivers/cpufreq/qcom-cpufreq-hw.c
@@ -10,18 +10,21 @@
  #include <linux/module.h>
  #include <linux/of_address.h>
  #include <linux/of_platform.h>
+#include <linux/pm_opp.h>
  #include <linux/slab.h>

  #define LUT_MAX_ENTRIES			40U
  #define LUT_SRC				GENMASK(31, 30)
  #define LUT_L_VAL			GENMASK(7, 0)
  #define LUT_CORE_COUNT			GENMASK(18, 16)
+#define LUT_VOLT			GENMASK(11, 0)
  #define LUT_ROW_SIZE			32
  #define CLK_HW_DIV			2

  /* Register offsets */
  #define REG_ENABLE			0x0
-#define REG_LUT_TABLE			0x110
+#define REG_FREQ_LUT_TABLE		0x110
+#define REG_VOLT_LUT_TABLE		0x114

The new names suggest that there is a LUT for frequencies and another
one for voltages. I don't have access to hardware documentation, but
from the code and offsets in this driver it seems there is a single
table at offset 0x110, with a 'row' of 32 bytes per OPP. Within this
row the frequency (and other values) is located at offset 0, the
voltage at offset 4.

I'd suggest to keep REG_LUT_TABLE, add a define LUT_OFFSET_VOLTAGE/MV
(or similar) and adjust the math in qcom_cpufreq_hw_read_lut() to use
REG_LUT_TABLE as base offset.


These names are as per HW documentation and the math is kept as per the documentation for reading the voltage.

  #define REG_PERF_STATE			0x920

  static unsigned long cpu_hw_rate, xo_rate;
@@ -75,19 +78,26 @@ static int qcom_cpufreq_hw_read_lut(struct device *dev,
  				    void __iomem *base)
  {
  	u32 data, src, lval, i, core_count, prev_cc = 0, prev_freq = 0, freq;
+	u32 volt;
  	unsigned int max_cores = cpumask_weight(policy->cpus);
  	struct cpufreq_frequency_table	*table;
+	unsigned long cpu_r;

nit: why 'cpu_r' and not just 'cpu'?

(if it is needed at all, see my comment below)


  	table = kcalloc(LUT_MAX_ENTRIES + 1, sizeof(*table), GFP_KERNEL);
  	if (!table)
  		return -ENOMEM;

  	for (i = 0; i < LUT_MAX_ENTRIES; i++) {
-		data = readl_relaxed(base + REG_LUT_TABLE + i * LUT_ROW_SIZE);
+		data = readl_relaxed(base + REG_FREQ_LUT_TABLE +
+				      i * LUT_ROW_SIZE);
  		src = FIELD_GET(LUT_SRC, data);
  		lval = FIELD_GET(LUT_L_VAL, data);
  		core_count = FIELD_GET(LUT_CORE_COUNT, data);

+		data = readl_relaxed(base + REG_VOLT_LUT_TABLE +
+				      i * LUT_ROW_SIZE);
+		volt = FIELD_GET(LUT_VOLT, data) * 1000;
+
  		if (src)
  			freq = xo_rate * lval / 1000;
  		else
@@ -123,6 +133,10 @@ static int qcom_cpufreq_hw_read_lut(struct device *dev,

  		prev_cc = core_count;
  		prev_freq = freq;
+
+		freq *= 1000;
+		for_each_cpu(cpu_r, policy->cpus)
+			dev_pm_opp_add(get_cpu_device(cpu_r), freq, volt);

Are you sure we want to duplicate the OPP entries for all CPUs in the
cluster? IIUC the frequencies of the cores in a cluster can't be
changed individually, hence the cores should have a shared table. I
think dev_pm_opp_get_sharing_cpus() does what you need.

You currently also add OPPs for invalid frequencies. From my SDM845
device:

cat /sys/devices/system/cpu/cpufreq/policy4/scaling_available_freq
   => 825600 902400 979200 1056000 1209600 1286400 1363200 1459200
   1536000 1612800 1689600 1766400 1843200 1920000 1996800 2092800
   2169600 2246400 2323200 2400000 2476800 2553600 2649600

cat /sys/devices/system/cpu/cpufreq/policy4/scaling_boost_frequencies
2803200

ls /sys/kernel/debug/opp/cpu4/
opp:1056000000  opp:1612800000  opp:2092800000  opp:2553600000  opp:825600000
opp:1209600000  opp:1689600000  opp:2169600000  opp:2649600000  opp:902400000
opp:1286400000  opp:1766400000  opp:2246400000  opp:2707200000  opp:979200000
opp:1363200000  opp:1843200000  opp:2323200000  opp:2764800000
opp:1459200000  opp:1920000000  opp:2400000000  opp:2784000000
opp:1536000000  opp:1996800000  opp:2476800000  opp:2803200000

There are OPP entries for 2707200000, 2764800000 and 2784000000 Hz,
however these frequencies appear neither in available_frequencies nor
boost_frequencies.

  	}


Could you help validating with the patch below?

  	table[i].frequency = CPUFREQ_TABLE_END;
@@ -159,10 +173,18 @@ static int qcom_cpufreq_hw_cpu_init(struct cpufreq_policy *policy)
  	struct device *dev = &global_pdev->dev;
  	struct of_phandle_args args;
  	struct device_node *cpu_np;
+	struct device *cpu_dev;
  	struct resource *res;
  	void __iomem *base;
  	int ret, index;

+	cpu_dev = get_cpu_device(policy->cpu);
+	if (!cpu_dev) {
+		pr_err("%s: failed to get cpu%d device\n", __func__,
+		       policy->cpu);
+		return -ENODEV;
+	}
+
  	cpu_np = of_cpu_device_node_get(policy->cpu);
  	if (!cpu_np)
  		return -EINVAL;
@@ -205,6 +227,12 @@ static int qcom_cpufreq_hw_cpu_init(struct cpufreq_policy *policy)
  		goto error;
  	}

+	ret = dev_pm_opp_get_opp_count(cpu_dev);
+	if (ret <= 0) {
+		dev_err(cpu_dev, "OPP table is not ready\n");
+		goto error;
+	}
+
  	policy->fast_switch_possible = true;

  	return 0;

I suppose we want to remove the OPPs when the cpufreq driver is
unloaded, looks like dev_pm_opp_cpumask_remove_table() should do the
trick.

Cheers

Matthias


diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c
index 7559b87..23338b2 100644
--- a/drivers/cpufreq/qcom-cpufreq-hw.c
+++ b/drivers/cpufreq/qcom-cpufreq-hw.c
@@ -81,7 +81,6 @@ static int qcom_cpufreq_hw_read_lut(struct device *dev,
        u32 volt;
        unsigned int max_cores = cpumask_weight(policy->cpus);
        struct cpufreq_frequency_table  *table;
-       unsigned long cpu_r;

        table = kcalloc(LUT_MAX_ENTRIES + 1, sizeof(*table), GFP_KERNEL);
        if (!table)
@@ -110,6 +109,8 @@ static int qcom_cpufreq_hw_read_lut(struct device *dev,
                        table[i].frequency = freq;
dev_dbg(dev, "index=%d freq=%d, core_count %d\n", i,
                                freq, core_count);
+                       dev_pm_opp_add(get_cpu_device(policy->cpu),
+                                       freq * 1000, volt);
                }

                /*
@@ -126,6 +127,8 @@ static int qcom_cpufreq_hw_read_lut(struct device *dev,
                        if (prev_cc != max_cores) {
                                prev->frequency = prev_freq;
                                prev->flags = CPUFREQ_BOOST_FREQ;
+                               dev_pm_opp_add(get_cpu_device(policy->cpu),
+                                               prev_freq * 1000, volt);
                        }

                        break;
@@ -133,12 +136,9 @@ static int qcom_cpufreq_hw_read_lut(struct device *dev,

                prev_cc = core_count;
                prev_freq = freq;
-
-               freq *= 1000;
-               for_each_cpu(cpu_r, policy->cpus)
-                       dev_pm_opp_add(get_cpu_device(cpu_r), freq, volt);
        }

+ dev_pm_opp_set_sharing_cpus(get_cpu_device(policy->cpu), policy->cpus);
        table[i].frequency = CPUFREQ_TABLE_END;
        policy->freq_table = table;

@@ -245,6 +245,7 @@ static int qcom_cpufreq_hw_cpu_exit(struct cpufreq_policy *policy)
 {
        void __iomem *base = policy->driver_data - REG_PERF_STATE;

+       dev_pm_opp_cpumask_remove_table(policy->cpus);
        kfree(policy->freq_table);
        devm_iounmap(&global_pdev->dev, base);

--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation.

--



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