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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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cpufreq: tegra194: use refclk delta based loop instead of udelay
Use reference clock count based loop instead of "udelay()" for sampling of counters to improve the accuracy of re-generated CPU frequency. "udelay()" internally calls "WFE" which stops the counters and results in bigger delta between the last set freq and the re-generated value from counters. The counter sampling window used in loop is the minimum number of reference clock cycles which is known to give a stable value of CPU frequency. The change also helps to reduce the sampling window from "500us" to "<50us". Suggested-by: Antti Miettinen <amiettinen@nvidia.com> Signed-off-by: Sumit Gupta <sumitg@nvidia.com> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
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parent
6b121b4cf7
commit
a60a556788
1 changed files with 55 additions and 17 deletions
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@ -5,7 +5,6 @@
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#include <linux/cpu.h>
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#include <linux/cpufreq.h>
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#include <linux/delay.h>
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#include <linux/dma-mapping.h>
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#include <linux/module.h>
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#include <linux/of.h>
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@ -21,10 +20,11 @@
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#define KHZ 1000
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#define REF_CLK_MHZ 408 /* 408 MHz */
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#define US_DELAY 500
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#define CPUFREQ_TBL_STEP_HZ (50 * KHZ * KHZ)
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#define MAX_CNT ~0U
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#define MAX_DELTA_KHZ 115200
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#define NDIV_MASK 0x1FF
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#define CORE_OFFSET(cpu) (cpu * 8)
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@ -68,6 +68,7 @@ struct tegra_cpufreq_soc {
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int maxcpus_per_cluster;
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unsigned int num_clusters;
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phys_addr_t actmon_cntr_base;
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u32 refclk_delta_min;
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};
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struct tegra194_cpufreq_data {
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@ -149,6 +150,8 @@ static void tegra234_read_counters(struct tegra_cpu_ctr *c)
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{
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struct tegra194_cpufreq_data *data = cpufreq_get_driver_data();
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void __iomem *actmon_reg;
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u32 delta_refcnt;
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int cnt = 0;
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u64 val;
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actmon_reg = CORE_ACTMON_CNTR_REG(data, data->cpu_data[c->cpu].clusterid,
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@ -157,10 +160,25 @@ static void tegra234_read_counters(struct tegra_cpu_ctr *c)
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val = readq(actmon_reg);
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c->last_refclk_cnt = upper_32_bits(val);
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c->last_coreclk_cnt = lower_32_bits(val);
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udelay(US_DELAY);
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val = readq(actmon_reg);
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c->refclk_cnt = upper_32_bits(val);
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c->coreclk_cnt = lower_32_bits(val);
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/*
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* The sampling window is based on the minimum number of reference
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* clock cycles which is known to give a stable value of CPU frequency.
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*/
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do {
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val = readq(actmon_reg);
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c->refclk_cnt = upper_32_bits(val);
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c->coreclk_cnt = lower_32_bits(val);
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if (c->refclk_cnt < c->last_refclk_cnt)
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delta_refcnt = c->refclk_cnt + (MAX_CNT - c->last_refclk_cnt);
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else
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delta_refcnt = c->refclk_cnt - c->last_refclk_cnt;
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if (++cnt >= 0xFFFF) {
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pr_warn("cpufreq: problem with refclk on cpu:%d, delta_refcnt:%u, cnt:%d\n",
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c->cpu, delta_refcnt, cnt);
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break;
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}
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} while (delta_refcnt < data->soc->refclk_delta_min);
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}
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static struct tegra_cpufreq_ops tegra234_cpufreq_ops = {
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@ -175,6 +193,7 @@ static const struct tegra_cpufreq_soc tegra234_cpufreq_soc = {
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.actmon_cntr_base = 0x9000,
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.maxcpus_per_cluster = 4,
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.num_clusters = 3,
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.refclk_delta_min = 16000,
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};
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static const struct tegra_cpufreq_soc tegra239_cpufreq_soc = {
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@ -182,6 +201,7 @@ static const struct tegra_cpufreq_soc tegra239_cpufreq_soc = {
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.actmon_cntr_base = 0x4000,
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.maxcpus_per_cluster = 8,
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.num_clusters = 1,
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.refclk_delta_min = 16000,
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};
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static void tegra194_get_cpu_cluster_id(u32 cpu, u32 *cpuid, u32 *clusterid)
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@ -222,15 +242,33 @@ static inline u32 map_ndiv_to_freq(struct mrq_cpu_ndiv_limits_response
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static void tegra194_read_counters(struct tegra_cpu_ctr *c)
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{
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struct tegra194_cpufreq_data *data = cpufreq_get_driver_data();
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u32 delta_refcnt;
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int cnt = 0;
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u64 val;
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val = read_freq_feedback();
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c->last_refclk_cnt = lower_32_bits(val);
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c->last_coreclk_cnt = upper_32_bits(val);
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udelay(US_DELAY);
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val = read_freq_feedback();
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c->refclk_cnt = lower_32_bits(val);
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c->coreclk_cnt = upper_32_bits(val);
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/*
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* The sampling window is based on the minimum number of reference
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* clock cycles which is known to give a stable value of CPU frequency.
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*/
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do {
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val = read_freq_feedback();
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c->refclk_cnt = lower_32_bits(val);
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c->coreclk_cnt = upper_32_bits(val);
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if (c->refclk_cnt < c->last_refclk_cnt)
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delta_refcnt = c->refclk_cnt + (MAX_CNT - c->last_refclk_cnt);
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else
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delta_refcnt = c->refclk_cnt - c->last_refclk_cnt;
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if (++cnt >= 0xFFFF) {
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pr_warn("cpufreq: problem with refclk on cpu:%d, delta_refcnt:%u, cnt:%d\n",
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c->cpu, delta_refcnt, cnt);
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break;
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}
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} while (delta_refcnt < data->soc->refclk_delta_min);
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}
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static void tegra_read_counters(struct work_struct *work)
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@ -288,9 +326,8 @@ static unsigned int tegra194_calculate_speed(u32 cpu)
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u32 rate_mhz;
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/*
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* udelay() is required to reconstruct cpu frequency over an
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* observation window. Using workqueue to call udelay() with
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* interrupts enabled.
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* Reconstruct cpu frequency over an observation/sampling window.
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* Using workqueue to keep interrupts enabled during the interval.
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*/
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read_counters_work.c.cpu = cpu;
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INIT_WORK_ONSTACK(&read_counters_work.work, tegra_read_counters);
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@ -372,9 +409,9 @@ static unsigned int tegra194_get_speed(u32 cpu)
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if (pos->driver_data != ndiv)
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continue;
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if (abs(pos->frequency - rate) > 115200) {
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pr_warn("cpufreq: cpu%d,cur:%u,set:%u,set ndiv:%llu\n",
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cpu, rate, pos->frequency, ndiv);
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if (abs(pos->frequency - rate) > MAX_DELTA_KHZ) {
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pr_warn("cpufreq: cpu%d,cur:%u,set:%u,delta:%d,set ndiv:%llu\n",
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cpu, rate, pos->frequency, abs(rate - pos->frequency), ndiv);
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} else {
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rate = pos->frequency;
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}
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@ -568,6 +605,7 @@ static const struct tegra_cpufreq_soc tegra194_cpufreq_soc = {
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.ops = &tegra194_cpufreq_ops,
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.maxcpus_per_cluster = 2,
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.num_clusters = 4,
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.refclk_delta_min = 16000,
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};
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static void tegra194_cpufreq_free_resources(void)
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@ -684,7 +722,7 @@ static int tegra194_cpufreq_probe(struct platform_device *pdev)
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soc = of_device_get_match_data(&pdev->dev);
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if (soc->ops && soc->maxcpus_per_cluster && soc->num_clusters) {
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if (soc->ops && soc->maxcpus_per_cluster && soc->num_clusters && soc->refclk_delta_min) {
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data->soc = soc;
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} else {
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dev_err(&pdev->dev, "soc data missing\n");
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