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

[Matthias Kaehlcke <mka@chromium.org>]

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@codeaurora.org>
> ---
>  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.

>  #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.

>  	}
> 
>  	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