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Date: Fri, 21 Dec 2018 12:57:52 -0800
From: Matthias Kaehlcke <mka@...omium.org>
To: Taniya Das <tdas@...eaurora.org>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Viresh Kumar <viresh.kumar@...aro.org>,
linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
Stephen Boyd <sboyd@...nel.org>,
Rajendra Nayak <rnayak@...eaurora.org>,
devicetree@...r.kernel.org, robh@...nel.org,
skannan@...eaurora.org, linux-arm-msm@...r.kernel.org,
amit.kucheria@...aro.org, evgreen@...gle.com
Subject: Re: [PATCH v1] cpufreq: qcom: Read voltage LUT and populate OPP
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@...eaurora.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
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