[TEGRA194_CPUFREQ PATCH v4 3/4] cpufreq: Add Tegra194 cpufreq driver

Sumit Gupta
2020-06-26T15:44:27Z

Add support for CPU frequency scaling on Tegra194. The frequency
of each core can be adjusted by writing a clock divisor value to
a MSR on the core. The range of valid divisors is queried from
the BPMP.

Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
---
drivers/cpufreq/Kconfig.arm | 6 +
drivers/cpufreq/Makefile | 1 +
drivers/cpufreq/tegra194-cpufreq.c | 396 +++++++++++++++++++++++++++++++++++++
3 files changed, 403 insertions(+)
create mode 100644 drivers/cpufreq/tegra194-cpufreq.c

diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index 15c1a12..f3d8f09 100644
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -314,6 +314,12 @@ config ARM_TEGRA186_CPUFREQ
help
This adds the CPUFreq driver support for Tegra186 SOCs.

+config ARM_TEGRA194_CPUFREQ
+ tristate "Tegra194 CPUFreq support"
+ depends on ARCH_TEGRA && TEGRA_BPMP
+ help
+ This adds CPU frequency driver support for Tegra194 SOCs.
+
config ARM_TI_CPUFREQ
bool "Texas Instruments CPUFreq support"
depends on ARCH_OMAP2PLUS
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index f6670c4..66b5563 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -83,6 +83,7 @@ obj-$(CONFIG_ARM_TANGO_CPUFREQ) += tango-cpufreq.o
obj-$(CONFIG_ARM_TEGRA20_CPUFREQ) += tegra20-cpufreq.o
obj-$(CONFIG_ARM_TEGRA124_CPUFREQ) += tegra124-cpufreq.o
obj-$(CONFIG_ARM_TEGRA186_CPUFREQ) += tegra186-cpufreq.o
+obj-$(CONFIG_ARM_TEGRA194_CPUFREQ) += tegra194-cpufreq.o
obj-$(CONFIG_ARM_TI_CPUFREQ) += ti-cpufreq.o
obj-$(CONFIG_ARM_VEXPRESS_SPC_CPUFREQ) += vexpress-spc-cpufreq.o

diff --git a/drivers/cpufreq/tegra194-cpufreq.c b/drivers/cpufreq/tegra194-cpufreq.c
new file mode 100644
index 0000000..77e422a
--- /dev/null
+++ b/drivers/cpufreq/tegra194-cpufreq.c
@@ -0,0 +1,396 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2020, NVIDIA CORPORATION. All rights reserved
+ */
+
+#include <linux/cpu.h>
+#include <linux/cpufreq.h>
+#include <linux/delay.h>
+#include <linux/dma-mapping.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#include <asm/smp_plat.h>
+
+#include <soc/tegra/bpmp.h>
+#include <soc/tegra/bpmp-abi.h>
+
+#define KHZ 1000
+#define REF_CLK_MHZ 408 /* 408 MHz */
+#define US_DELAY 500
+#define US_DELAY_MIN 2
+#define CPUFREQ_TBL_STEP_HZ (50 * KHZ * KHZ)
+#define MAX_CNT ~0U
+
+/* cpufreq transisition latency */
+#define TEGRA_CPUFREQ_TRANSITION_LATENCY (300 * 1000) /* unit in nanoseconds */
+
+enum cluster {
+ CLUSTER0,
+ CLUSTER1,
+ CLUSTER2,
+ CLUSTER3,
+ MAX_CLUSTERS,
+};
+
+struct tegra194_cpufreq_data {
+ void __iomem *regs;
+ size_t num_clusters;
+ struct cpufreq_frequency_table **tables;
+};
+
+struct tegra_cpu_ctr {
+ u32 cpu;
+ u32 delay;
+ u32 coreclk_cnt, last_coreclk_cnt;
+ u32 refclk_cnt, last_refclk_cnt;
+};
+
+struct read_counters_work {
+ struct work_struct work;
+ struct tegra_cpu_ctr c;
+};
+
+static struct workqueue_struct *read_counters_wq;
+
+static enum cluster get_cpu_cluster(u8 cpu)
+{
+ return MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1);
+}
+
+/*
+ * Read per-core Read-only system register NVFREQ_FEEDBACK_EL1.
+ * The register provides frequency feedback information to
+ * determine the average actual frequency a core has run at over
+ * a period of time.
+ * [31:0] PLLP counter: Counts at fixed frequency (408 MHz)
+ * [63:32] Core clock counter: counts on every core clock cycle
+ * where the core is architecturally clocking
+ */
+static u64 read_freq_feedback(void)
+{
+ u64 val = 0;
+
+ asm volatile("mrs %0, s3_0_c15_c0_5" : "=r" (val) : );
+
+ return val;
+}
+
+static inline u32 map_ndiv_to_freq(struct mrq_cpu_ndiv_limits_response
+ *nltbl, u16 ndiv)
+{
+ return nltbl->ref_clk_hz / KHZ * ndiv / (nltbl->pdiv * nltbl->mdiv);
+}
+
+static void tegra_read_counters(struct work_struct *work)
+{
+ struct read_counters_work *read_counters_work;
+ struct tegra_cpu_ctr *c;
+ u64 val;
+
+ /*
+ * ref_clk_counter(32 bit counter) runs on constant clk,
+ * pll_p(408MHz).
+ * It will take = 2 ^ 32 / 408 MHz to overflow ref clk counter
+ * = 10526880 usec = 10.527 sec to overflow
+ *
+ * Like wise core_clk_counter(32 bit counter) runs on core clock.
+ * It's synchronized to crab_clk (cpu_crab_clk) which runs at
+ * freq of cluster. Assuming max cluster clock ~2000MHz,
+ * It will take = 2 ^ 32 / 2000 MHz to overflow core clk counter
+ * = ~2.147 sec to overflow
+ */
+ read_counters_work = container_of(work, struct read_counters_work,
+ work);
+ c = &read_counters_work->c;
+
+ val = read_freq_feedback();
+ c->last_refclk_cnt = lower_32_bits(val);
+ c->last_coreclk_cnt = upper_32_bits(val);
+ udelay(c->delay);
+ val = read_freq_feedback();
+ c->refclk_cnt = lower_32_bits(val);
+ c->coreclk_cnt = upper_32_bits(val);
+}
+
+/*
+ * Return instantaneous cpu speed
+ * Instantaneous freq is calculated as -
+ * -Takes sample on every query of getting the freq.
+ * - Read core and ref clock counters;
+ * - Delay for X us
+ * - Read above cycle counters again
+ * - Calculates freq by subtracting current and previous counters
+ * divided by the delay time or eqv. of ref_clk_counter in delta time
+ * - Return Kcycles/second, freq in KHz
+ *
+ * delta time period = x sec
+ * = delta ref_clk_counter / (408 * 10^6) sec
+ * freq in Hz = cycles/sec
+ * = (delta cycles / x sec
+ * = (delta cycles * 408 * 10^6) / delta ref_clk_counter
+ * in KHz = (delta cycles * 408 * 10^3) / delta ref_clk_counter
+ *
+ * @cpu - logical cpu whose freq to be updated
+ * Returns freq in KHz on success, 0 if cpu is offline
+ */
+static unsigned int tegra194_get_speed_common(u32 cpu, u32 delay)
+{
+ struct read_counters_work read_counters_work;
+ struct tegra_cpu_ctr c;
+ u32 delta_refcnt;
+ u32 delta_ccnt;
+ u32 rate_mhz;
+
+ /*
+ * udelay() is required to reconstruct cpu frequency over an
+ * observation window. Using workqueue to call udelay() with
+ * interrupts enabled.
+ */
+ read_counters_work.c.cpu = cpu;
+ read_counters_work.c.delay = delay;
+ INIT_WORK_ONSTACK(&read_counters_work.work, tegra_read_counters);
+ queue_work_on(cpu, read_counters_wq, &read_counters_work.work);
+ flush_work(&read_counters_work.work);
+ c = read_counters_work.c;
+
+ if (c.coreclk_cnt < c.last_coreclk_cnt)
+ delta_ccnt = c.coreclk_cnt + (MAX_CNT - c.last_coreclk_cnt);
+ else
+ delta_ccnt = c.coreclk_cnt - c.last_coreclk_cnt;
+ if (!delta_ccnt)
+ return 0;
+
+ /* ref clock is 32 bits */
+ if (c.refclk_cnt < c.last_refclk_cnt)
+ delta_refcnt = c.refclk_cnt + (MAX_CNT - c.last_refclk_cnt);
+ else
+ delta_refcnt = c.refclk_cnt - c.last_refclk_cnt;
+ if (!delta_refcnt) {
+ pr_debug("cpufreq: %d is idle, delta_refcnt: 0\n", cpu);
+ return 0;
+ }
+ rate_mhz = ((unsigned long)(delta_ccnt * REF_CLK_MHZ)) / delta_refcnt;
+
+ return (rate_mhz * KHZ); /* in KHz */
+}
+
+static unsigned int tegra194_get_speed(u32 cpu)
+{
+ return tegra194_get_speed_common(cpu, US_DELAY);
+}
+
+static unsigned int tegra194_fast_get_speed(u32 cpu)
+{
+ return tegra194_get_speed_common(cpu, US_DELAY_MIN);
+}
+
+static int tegra194_cpufreq_init(struct cpufreq_policy *policy)
+{
+ struct tegra194_cpufreq_data *data = cpufreq_get_driver_data();
+ int cl = get_cpu_cluster(policy->cpu);
+ u32 cpu;
+
+ if (cl >= data->num_clusters)
+ return -EINVAL;
+
+ policy->cur = tegra194_fast_get_speed(policy->cpu); /* boot freq */
+
+ /* set same policy for all cpus in a cluster */
+ for (cpu = (cl * 2); cpu < ((cl + 1) * 2); cpu++)
+ cpumask_set_cpu(cpu, policy->cpus);
+
+ policy->freq_table = data->tables[cl];
+ policy->cpuinfo.transition_latency = TEGRA_CPUFREQ_TRANSITION_LATENCY;
+
+ return 0;
+}
+
+static void set_cpu_ndiv(void *data)
+{
+ struct cpufreq_frequency_table *tbl = data;
+ u64 ndiv_val = (u64)tbl->driver_data;
+
+ asm volatile("msr s3_0_c15_c0_4, %0" : : "r" (ndiv_val));
+}
+
+static int tegra194_cpufreq_set_target(struct cpufreq_policy *policy,
+ unsigned int index)
+{
+ struct cpufreq_frequency_table *tbl = policy->freq_table + index;
+
+ /*
+ * Each core writes frequency in per core register. Then both cores
+ * in a cluster run at same frequency which is the maximum frequency
+ * request out of the values requested by both cores in that cluster.
+ */
+ on_each_cpu_mask(policy->cpus, set_cpu_ndiv, tbl, true);
+
+ return 0;
+}
+
+static struct cpufreq_driver tegra194_cpufreq_driver = {
+ .name = "tegra194",
+ .flags = CPUFREQ_STICKY | CPUFREQ_CONST_LOOPS |
+ CPUFREQ_NEED_INITIAL_FREQ_CHECK,
+ .verify = cpufreq_generic_frequency_table_verify,
+ .target_index = tegra194_cpufreq_set_target,
+ .get = tegra194_get_speed,
+ .init = tegra194_cpufreq_init,
+ .attr = cpufreq_generic_attr,
+};
+
+static void tegra194_cpufreq_free_resources(void)
+{
+ destroy_workqueue(read_counters_wq);
+}
+
+static struct cpufreq_frequency_table *
+init_freq_table(struct platform_device *pdev, struct tegra_bpmp *bpmp,
+ unsigned int cluster_id)
+{
+ struct cpufreq_frequency_table *freq_table;
+ struct mrq_cpu_ndiv_limits_response resp;
+ unsigned int num_freqs, ndiv, delta_ndiv;
+ struct mrq_cpu_ndiv_limits_request req;
+ struct tegra_bpmp_message msg;
+ u16 freq_table_step_size;
+ int err, index;
+
+ memset(&req, 0, sizeof(req));
+ req.cluster_id = cluster_id;
+
+ memset(&msg, 0, sizeof(msg));
+ msg.mrq = MRQ_CPU_NDIV_LIMITS;
+ msg.tx.data = &req;
+ msg.tx.size = sizeof(req);
+ msg.rx.data = &resp;
+ msg.rx.size = sizeof(resp);
+
+ err = tegra_bpmp_transfer(bpmp, &msg);
+ if (err)
+ return ERR_PTR(err);
+
+ /*
+ * Make sure frequency table step is a multiple of mdiv to match
+ * vhint table granularity.
+ */
+ freq_table_step_size = resp.mdiv *
+ DIV_ROUND_UP(CPUFREQ_TBL_STEP_HZ, resp.ref_clk_hz);
+
+ dev_dbg(&pdev->dev, "cluster %d: frequency table step size: %d\n",
+ cluster_id, freq_table_step_size);
+
+ delta_ndiv = resp.ndiv_max - resp.ndiv_min;
+
+ if (unlikely(delta_ndiv == 0))
+ num_freqs = 1;
+ else
+ /* We store both ndiv_min and ndiv_max hence the +1 */
+ num_freqs = delta_ndiv / freq_table_step_size + 1;
+
+ num_freqs += (delta_ndiv % freq_table_step_size) ? 1 : 0;
+
+ freq_table = devm_kcalloc(&pdev->dev, num_freqs + 1,
+ sizeof(*freq_table), GFP_KERNEL);
+ if (!freq_table)
+ return ERR_PTR(-ENOMEM);
+
+ for (index = 0, ndiv = resp.ndiv_min;
+ ndiv < resp.ndiv_max;
+ index++, ndiv += freq_table_step_size) {
+ freq_table[index].driver_data = ndiv;
+ freq_table[index].frequency = map_ndiv_to_freq(&resp, ndiv);
+ }
+
+ freq_table[index].driver_data = resp.ndiv_max;
+ freq_table[index++].frequency = map_ndiv_to_freq(&resp, resp.ndiv_max);
+ freq_table[index].frequency = CPUFREQ_TABLE_END;
+
+ return freq_table;
+}
+
+static int tegra194_cpufreq_probe(struct platform_device *pdev)
+{
+ struct tegra194_cpufreq_data *data;
+ struct tegra_bpmp *bpmp;
+ int err, i;
+
+ data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ data->num_clusters = MAX_CLUSTERS;
+ data->tables = devm_kcalloc(&pdev->dev, data->num_clusters,
+ sizeof(*data->tables), GFP_KERNEL);
+ if (!data->tables)
+ return -ENOMEM;
+
+ platform_set_drvdata(pdev, data);
+
+ bpmp = tegra_bpmp_get(&pdev->dev);
+ if (IS_ERR(bpmp))
+ return PTR_ERR(bpmp);
+
+ read_counters_wq = alloc_workqueue("read_counters_wq", __WQ_LEGACY, 1);
+ if (!read_counters_wq) {
+ dev_err(&pdev->dev, "fail to create_workqueue\n");
+ err = -EINVAL;
+ goto put_bpmp;
+ }
+
+ for (i = 0; i < data->num_clusters; i++) {
+ data->tables[i] = init_freq_table(pdev, bpmp, i);
+ if (IS_ERR(data->tables[i])) {
+ err = PTR_ERR(data->tables[i]);
+ goto put_bpmp;
+ }
+ }
+
+ tegra_bpmp_put(bpmp);
+
+ tegra194_cpufreq_driver.driver_data = data;
+
+ err = cpufreq_register_driver(&tegra194_cpufreq_driver);
+ if (err)
+ goto put_bpmp;
+
+ return err;
+
+put_bpmp:
+ tegra_bpmp_put(bpmp);
+ tegra194_cpufreq_free_resources();
+ return err;
+}
+
+static int tegra194_cpufreq_remove(struct platform_device *pdev)
+{
+ cpufreq_unregister_driver(&tegra194_cpufreq_driver);
+ tegra194_cpufreq_free_resources();
+
+ return 0;
+}
+
+static const struct of_device_id tegra194_cpufreq_of_match[] = {
+ { .compatible = "nvidia,tegra194-ccplex", },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, tegra194_cpufreq_of_match);
+
+static struct platform_driver tegra194_ccplex_driver = {
+ .driver = {
+ .name = "tegra194-cpufreq",
+ .of_match_table = tegra194_cpufreq_of_match,
+ },
+ .probe = tegra194_cpufreq_probe,
+ .remove = tegra194_cpufreq_remove,
+};
+module_platform_driver(tegra194_ccplex_driver);
+
+MODULE_AUTHOR("Mikko Perttunen <mperttunen@nvidia.com>");
+MODULE_AUTHOR("Sumit Gupta <sumitg@nvidia.com>");
+MODULE_DESCRIPTION("NVIDIA Tegra194 cpufreq driver");
+MODULE_LICENSE("GPL v2");
--
2.7.4