Re: [PATCH v3 4/5] cpufreq: apple-soc: Add new driver to control Apple SoC CPU P-states
From: Ulf Hansson
Date: Tue Nov 01 2022 - 11:19:31 EST
On Mon, 24 Oct 2022 at 06:40, Hector Martin <marcan@xxxxxxxxx> wrote:
>
> This driver implements CPU frequency scaling for Apple Silicon SoCs,
> including M1 (t8103), M1 Max/Pro/Ultra (t600x), and M2 (t8112).
>
> Each CPU cluster has its own register set, and frequency management is
> fully automated by the hardware; the driver only has to write one
> register. There is boost frequency support, but the hardware will only
> allow their use if only a subset of cores in a cluster are in
> non-deep-idle. Since we don't support deep idle yet, these frequencies
> are not achievable, but the driver supports them. They will remain
> disabled in the device tree until deep idle is implemented, to avoid
> confusing users.
Out of curiosity, may I ask if this implies the need of a
synchronization mechanism on the Linux side? Or is the boost frequency
dynamically managed solely by HW/FW?
>
> This driver does not yet implement the memory controller performance
> state tuning that usually accompanies higher CPU p-states. This will be
> done in a future patch.
>
> Signed-off-by: Hector Martin <marcan@xxxxxxxxx>
Other than the question above, I intend to help to review the series
in more detail soon.
Kind regards
Uffe
> ---
> drivers/cpufreq/Kconfig.arm | 9 +
> drivers/cpufreq/Makefile | 1 +
> drivers/cpufreq/apple-soc-cpufreq.c | 352 +++++++++++++++++++++++++++
> drivers/cpufreq/cpufreq-dt-platdev.c | 2 +
> 4 files changed, 364 insertions(+)
> create mode 100644 drivers/cpufreq/apple-soc-cpufreq.c
>
> diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
> index 82e5de1f6f8c..29969f84008a 100644
> --- a/drivers/cpufreq/Kconfig.arm
> +++ b/drivers/cpufreq/Kconfig.arm
> @@ -41,6 +41,15 @@ config ARM_ALLWINNER_SUN50I_CPUFREQ_NVMEM
> To compile this driver as a module, choose M here: the
> module will be called sun50i-cpufreq-nvmem.
>
> +config ARM_APPLE_SOC_CPUFREQ
> + tristate "Apple Silicon SoC CPUFreq support"
> + depends on ARCH_APPLE || (COMPILE_TEST && 64BIT)
> + select PM_OPP
> + default ARCH_APPLE
> + help
> + This adds the CPUFreq driver for Apple Silicon machines
> + (e.g. Apple M1).
> +
> config ARM_ARMADA_37XX_CPUFREQ
> tristate "Armada 37xx CPUFreq support"
> depends on ARCH_MVEBU && CPUFREQ_DT
> diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
> index 49b98c62c5af..32a7029e25ed 100644
> --- a/drivers/cpufreq/Makefile
> +++ b/drivers/cpufreq/Makefile
> @@ -52,6 +52,7 @@ obj-$(CONFIG_X86_AMD_FREQ_SENSITIVITY) += amd_freq_sensitivity.o
>
> ##################################################################################
> # ARM SoC drivers
> +obj-$(CONFIG_ARM_APPLE_SOC_CPUFREQ) += apple-soc-cpufreq.o
> obj-$(CONFIG_ARM_ARMADA_37XX_CPUFREQ) += armada-37xx-cpufreq.o
> obj-$(CONFIG_ARM_ARMADA_8K_CPUFREQ) += armada-8k-cpufreq.o
> obj-$(CONFIG_ARM_BRCMSTB_AVS_CPUFREQ) += brcmstb-avs-cpufreq.o
> diff --git a/drivers/cpufreq/apple-soc-cpufreq.c b/drivers/cpufreq/apple-soc-cpufreq.c
> new file mode 100644
> index 000000000000..12c4b490edb8
> --- /dev/null
> +++ b/drivers/cpufreq/apple-soc-cpufreq.c
> @@ -0,0 +1,352 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Apple SoC CPU cluster performance state driver
> + *
> + * Copyright The Asahi Linux Contributors
> + *
> + * Based on scpi-cpufreq.c
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/bitops.h>
> +#include <linux/cpu.h>
> +#include <linux/cpufreq.h>
> +#include <linux/cpumask.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/iopoll.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/pm_opp.h>
> +#include <linux/slab.h>
> +
> +#define APPLE_DVFS_CMD 0x20
> +#define APPLE_DVFS_CMD_BUSY BIT(31)
> +#define APPLE_DVFS_CMD_SET BIT(25)
> +#define APPLE_DVFS_CMD_PS2 GENMASK(16, 12)
> +#define APPLE_DVFS_CMD_PS1 GENMASK(4, 0)
> +
> +/* Same timebase as CPU counter (24MHz) */
> +#define APPLE_DVFS_LAST_CHG_TIME 0x38
> +
> +/*
> + * Apple ran out of bits and had to shift this in T8112...
> + */
> +#define APPLE_DVFS_STATUS 0x50
> +#define APPLE_DVFS_STATUS_CUR_PS_T8103 GENMASK(7, 4)
> +#define APPLE_DVFS_STATUS_CUR_PS_SHIFT_T8103 4
> +#define APPLE_DVFS_STATUS_TGT_PS_T8103 GENMASK(3, 0)
> +#define APPLE_DVFS_STATUS_CUR_PS_T8112 GENMASK(9, 5)
> +#define APPLE_DVFS_STATUS_CUR_PS_SHIFT_T8112 5
> +#define APPLE_DVFS_STATUS_TGT_PS_T8112 GENMASK(4, 0)
> +
> +/*
> + * Div is +1, base clock is 12MHz on existing SoCs.
> + * For documentation purposes. We use the OPP table to
> + * get the frequency.
> + */
> +#define APPLE_DVFS_PLL_STATUS 0xc0
> +#define APPLE_DVFS_PLL_FACTOR 0xc8
> +#define APPLE_DVFS_PLL_FACTOR_MULT GENMASK(31, 16)
> +#define APPLE_DVFS_PLL_FACTOR_DIV GENMASK(15, 0)
> +
> +#define APPLE_DVFS_TRANSITION_TIMEOUT 100
> +
> +struct apple_soc_cpufreq_info {
> + u64 max_pstate;
> + u64 cur_pstate_mask;
> + u64 cur_pstate_shift;
> +};
> +
> +struct apple_cpu_priv {
> + struct device *cpu_dev;
> + void __iomem *reg_base;
> + const struct apple_soc_cpufreq_info *info;
> +};
> +
> +static struct cpufreq_driver apple_soc_cpufreq_driver;
> +
> +const struct apple_soc_cpufreq_info soc_t8103_info = {
> + .max_pstate = 15,
> + .cur_pstate_mask = APPLE_DVFS_STATUS_CUR_PS_T8103,
> + .cur_pstate_shift = APPLE_DVFS_STATUS_CUR_PS_SHIFT_T8103,
> +};
> +
> +const struct apple_soc_cpufreq_info soc_t8112_info = {
> + .max_pstate = 31,
> + .cur_pstate_mask = APPLE_DVFS_STATUS_CUR_PS_T8112,
> + .cur_pstate_shift = APPLE_DVFS_STATUS_CUR_PS_SHIFT_T8112,
> +};
> +
> +const struct apple_soc_cpufreq_info soc_default_info = {
> + .max_pstate = 15,
> + .cur_pstate_mask = 0, /* fallback */
> +};
> +
> +static const struct of_device_id apple_soc_cpufreq_of_match[] = {
> + {
> + .compatible = "apple,t8103-cluster-cpufreq",
> + .data = &soc_t8103_info,
> + },
> + {
> + .compatible = "apple,t8112-cluster-cpufreq",
> + .data = &soc_t8112_info,
> + },
> + {
> + .compatible = "apple,cluster-cpufreq",
> + .data = &soc_default_info,
> + },
> + {}
> +};
> +
> +static unsigned int apple_soc_cpufreq_get_rate(unsigned int cpu)
> +{
> + struct cpufreq_policy *policy = cpufreq_cpu_get_raw(cpu);
> + struct apple_cpu_priv *priv = policy->driver_data;
> + unsigned int pstate;
> + unsigned int i;
> +
> + if (priv->info->cur_pstate_mask) {
> + u64 reg = readq_relaxed(priv->reg_base + APPLE_DVFS_STATUS);
> +
> + pstate = (reg & priv->info->cur_pstate_mask) >> priv->info->cur_pstate_shift;
> + } else {
> + /*
> + * For the fallback case we might not know the layout of DVFS_STATUS,
> + * so just use the command register value (which ignores boost limitations).
> + */
> + u64 reg = readq_relaxed(priv->reg_base + APPLE_DVFS_CMD);
> +
> + pstate = FIELD_GET(APPLE_DVFS_CMD_PS1, reg);
> + }
> +
> + for (i = 0; policy->freq_table[i].frequency != CPUFREQ_TABLE_END; i++)
> + if (policy->freq_table[i].driver_data == pstate)
> + return policy->freq_table[i].frequency;
> +
> + dev_err(priv->cpu_dev, "could not find frequency for pstate %d\n",
> + pstate);
> + return 0;
> +}
> +
> +static int apple_soc_cpufreq_set_target(struct cpufreq_policy *policy,
> + unsigned int index)
> +{
> + struct apple_cpu_priv *priv = policy->driver_data;
> + unsigned int pstate = policy->freq_table[index].driver_data;
> + u64 reg;
> +
> + /* Fallback for newer SoCs */
> + if (index > priv->info->max_pstate)
> + index = priv->info->max_pstate;
> +
> + if (readq_poll_timeout_atomic(priv->reg_base + APPLE_DVFS_CMD, reg,
> + !(reg & APPLE_DVFS_CMD_BUSY), 2,
> + APPLE_DVFS_TRANSITION_TIMEOUT)) {
> + return -EIO;
> + }
> +
> + reg &= ~(APPLE_DVFS_CMD_PS1 | APPLE_DVFS_CMD_PS2);
> + reg |= FIELD_PREP(APPLE_DVFS_CMD_PS1, pstate);
> + reg |= FIELD_PREP(APPLE_DVFS_CMD_PS2, pstate);
> + reg |= APPLE_DVFS_CMD_SET;
> +
> + writeq_relaxed(reg, priv->reg_base + APPLE_DVFS_CMD);
> +
> + return 0;
> +}
> +
> +static unsigned int apple_soc_cpufreq_fast_switch(struct cpufreq_policy *policy,
> + unsigned int target_freq)
> +{
> + if (apple_soc_cpufreq_set_target(policy, policy->cached_resolved_idx) < 0)
> + return 0;
> +
> + return policy->freq_table[policy->cached_resolved_idx].frequency;
> +}
> +
> +static int apple_soc_cpufreq_find_cluster(struct cpufreq_policy *policy,
> + void __iomem **reg_base,
> + const struct apple_soc_cpufreq_info **info)
> +{
> + struct of_phandle_args args;
> + const struct of_device_id *match;
> + int ret = 0;
> +
> + ret = of_perf_domain_get_sharing_cpumask(policy->cpu, "performance-domains",
> + "#performance-domain-cells",
> + policy->cpus, &args);
> + if (ret < 0)
> + return ret;
> +
> + match = of_match_node(apple_soc_cpufreq_of_match, args.np);
> + of_node_put(args.np);
> + if (!match)
> + return -ENODEV;
> +
> + *info = match->data;
> +
> + *reg_base = of_iomap(args.np, 0);
> + if (IS_ERR(*reg_base))
> + return PTR_ERR(*reg_base);
> +
> + return 0;
> +}
> +
> +static struct freq_attr *apple_soc_cpufreq_hw_attr[] = {
> + &cpufreq_freq_attr_scaling_available_freqs,
> + NULL,
> + NULL,
> +};
> +
> +static int apple_soc_cpufreq_init(struct cpufreq_policy *policy)
> +{
> + int ret, i;
> + unsigned int transition_latency;
> + void __iomem *reg_base;
> + struct device *cpu_dev;
> + struct apple_cpu_priv *priv;
> + const struct apple_soc_cpufreq_info *info;
> + struct cpufreq_frequency_table *freq_table;
> +
> + cpu_dev = get_cpu_device(policy->cpu);
> + if (!cpu_dev) {
> + pr_err("failed to get cpu%d device\n", policy->cpu);
> + return -ENODEV;
> + }
> +
> + ret = dev_pm_opp_of_add_table(cpu_dev);
> + if (ret < 0) {
> + dev_err(cpu_dev, "%s: failed to add OPP table: %d\n", __func__, ret);
> + return ret;
> + }
> +
> + ret = apple_soc_cpufreq_find_cluster(policy, ®_base, &info);
> + if (ret) {
> + dev_err(cpu_dev, "%s: failed to get cluster info: %d\n", __func__, ret);
> + return ret;
> + }
> +
> + ret = dev_pm_opp_set_sharing_cpus(cpu_dev, policy->cpus);
> + if (ret) {
> + dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n", __func__, ret);
> + goto out_iounmap;
> + }
> +
> + ret = dev_pm_opp_get_opp_count(cpu_dev);
> + if (ret <= 0) {
> + dev_dbg(cpu_dev, "OPP table is not ready, deferring probe\n");
> + ret = -EPROBE_DEFER;
> + goto out_free_opp;
> + }
> +
> + priv = kzalloc(sizeof(*priv), GFP_KERNEL);
> + if (!priv) {
> + ret = -ENOMEM;
> + goto out_free_opp;
> + }
> +
> + ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
> + if (ret) {
> + dev_err(cpu_dev, "failed to init cpufreq table: %d\n", ret);
> + goto out_free_priv;
> + }
> +
> + /* Get OPP levels (p-state indexes) and stash them in driver_data */
> + for (i = 0; freq_table[i].frequency != CPUFREQ_TABLE_END; i++) {
> + unsigned long rate = freq_table[i].frequency * 1000;
> + struct dev_pm_opp *opp = dev_pm_opp_find_freq_floor(cpu_dev, &rate);
> +
> + if (IS_ERR(opp)) {
> + ret = PTR_ERR(opp);
> + goto out_free_cpufreq_table;
> + }
> + freq_table[i].driver_data = dev_pm_opp_get_level(opp);
> + dev_pm_opp_put(opp);
> + }
> +
> + priv->cpu_dev = cpu_dev;
> + priv->reg_base = reg_base;
> + priv->info = info;
> + policy->driver_data = priv;
> + policy->freq_table = freq_table;
> +
> + transition_latency = dev_pm_opp_get_max_transition_latency(cpu_dev);
> + if (!transition_latency)
> + transition_latency = CPUFREQ_ETERNAL;
> +
> + policy->cpuinfo.transition_latency = transition_latency;
> + policy->dvfs_possible_from_any_cpu = true;
> + policy->fast_switch_possible = true;
> +
> + if (policy_has_boost_freq(policy)) {
> + ret = cpufreq_enable_boost_support();
> + if (ret) {
> + dev_warn(cpu_dev, "failed to enable boost: %d\n", ret);
> + } else {
> + apple_soc_cpufreq_hw_attr[1] = &cpufreq_freq_attr_scaling_boost_freqs;
> + apple_soc_cpufreq_driver.boost_enabled = true;
> + }
> + }
> +
> + return 0;
> +
> +out_free_cpufreq_table:
> + dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
> +out_free_priv:
> + kfree(priv);
> +out_free_opp:
> + dev_pm_opp_remove_all_dynamic(cpu_dev);
> +out_iounmap:
> + iounmap(reg_base);
> + return ret;
> +}
> +
> +static int apple_soc_cpufreq_exit(struct cpufreq_policy *policy)
> +{
> + struct apple_cpu_priv *priv = policy->driver_data;
> +
> + dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
> + dev_pm_opp_remove_all_dynamic(priv->cpu_dev);
> + iounmap(priv->reg_base);
> + kfree(priv);
> +
> + return 0;
> +}
> +
> +static struct cpufreq_driver apple_soc_cpufreq_driver = {
> + .name = "apple-cpufreq",
> + .flags = CPUFREQ_HAVE_GOVERNOR_PER_POLICY |
> + CPUFREQ_NEED_INITIAL_FREQ_CHECK | CPUFREQ_IS_COOLING_DEV,
> + .verify = cpufreq_generic_frequency_table_verify,
> + .attr = cpufreq_generic_attr,
> + .get = apple_soc_cpufreq_get_rate,
> + .init = apple_soc_cpufreq_init,
> + .exit = apple_soc_cpufreq_exit,
> + .target_index = apple_soc_cpufreq_set_target,
> + .fast_switch = apple_soc_cpufreq_fast_switch,
> + .register_em = cpufreq_register_em_with_opp,
> + .attr = apple_soc_cpufreq_hw_attr,
> +};
> +
> +static int __init apple_soc_cpufreq_module_init(void)
> +{
> + if (!of_machine_is_compatible("apple,arm-platform"))
> + return -ENODEV;
> +
> + return cpufreq_register_driver(&apple_soc_cpufreq_driver);
> +}
> +module_init(apple_soc_cpufreq_module_init);
> +
> +static void __exit apple_soc_cpufreq_module_exit(void)
> +{
> + cpufreq_unregister_driver(&apple_soc_cpufreq_driver);
> +}
> +module_exit(apple_soc_cpufreq_module_exit);
> +
> +MODULE_DEVICE_TABLE(of, apple_soc_cpufreq_of_match);
> +MODULE_AUTHOR("Hector Martin <marcan@xxxxxxxxx>");
> +MODULE_DESCRIPTION("Apple SoC CPU cluster DVFS driver");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/cpufreq/cpufreq-dt-platdev.c b/drivers/cpufreq/cpufreq-dt-platdev.c
> index 6ac3800db450..a108b9796770 100644
> --- a/drivers/cpufreq/cpufreq-dt-platdev.c
> +++ b/drivers/cpufreq/cpufreq-dt-platdev.c
> @@ -103,6 +103,8 @@ static const struct of_device_id allowlist[] __initconst = {
> static const struct of_device_id blocklist[] __initconst = {
> { .compatible = "allwinner,sun50i-h6", },
>
> + { .compatible = "apple,arm-platform", },
> +
> { .compatible = "arm,vexpress", },
>
> { .compatible = "calxeda,highbank", },
> --
> 2.35.1
>