linux/drivers/cpufreq/cppc_cpufreq.c, branch v5.19

cpufreq: CPPC: Fix unused-function warning

2022-05-30T13:33:42Z

Building the cppc_cpufreq driver with for arm64 with CONFIG_ENERGY_MODEL=n triggers the following warnings: drivers/cpufreq/cppc_cpufreq.c:550:12: error: ‘cppc_get_cpu_cost’ defined but not used [-Werror=unused-function] 550 | static int cppc_get_cpu_cost(struct device *cpu_dev, unsigned long KHz, | ^~~~~~~~~~~~~~~~~ drivers/cpufreq/cppc_cpufreq.c:481:12: error: ‘cppc_get_cpu_power’ defined but not used [-Werror=unused-function] 481 | static int cppc_get_cpu_power(struct device *cpu_dev, | ^~~~~~~~~~~~~~~~~~ Move the Energy Model related functions into specific guards. This allows to fix the warning and prevent doing extra work when the Energy Model is not present. Fixes: 740fcdc2c20e ("cpufreq: CPPC: Register EM based on efficiency class information") Reported-by: Shaokun Zhang Signed-off-by: Pierre Gondois Tested-by: Shaokun Zhang Signed-off-by: Rafael J. Wysocki

cpufreq: CPPC: Fix build error without CONFIG_ACPI_CPPC_CPUFREQ_FIE

2022-05-30T13:31:28Z

If CONFIG_ACPI_CPPC_CPUFREQ_FIE is not set, building fails: drivers/cpufreq/cppc_cpufreq.c: In function ‘populate_efficiency_class’: drivers/cpufreq/cppc_cpufreq.c:584:2: error: ‘cppc_cpufreq_driver’ undeclared (first use in this function); did you mean ‘cpufreq_driver’? cppc_cpufreq_driver.register_em = cppc_cpufreq_register_em; ^~~~~~~~~~~~~~~~~~~ cpufreq_driver Make declare of cppc_cpufreq_driver out of CONFIG_ACPI_CPPC_CPUFREQ_FIE to fix this. Fixes: 740fcdc2c20e ("cpufreq: CPPC: Register EM based on efficiency class information") Signed-off-by: Zheng Bin Acked-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki

cpufreq: CPPC: Enable dvfs_possible_from_any_cpu

2022-05-19T17:45:34Z

The communication mean of the _CPC desired performance can be PCC, System Memory, System IO, or Functional Fixed Hardware (FFH). PCC, SystemMemory and SystemIo address spaces are available from any CPU. Thus, dvfs_possible_from_any_cpu should be enabled in such case. For FFH, let the FFH implementation do smp_call_function_*() calls. Signed-off-by: Pierre Gondois Reviewed-by: Sudeep Holla Acked-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki

cpufreq: CPPC: Enable fast_switch

2022-05-19T17:45:34Z

The communication mean of the _CPC desired performance can be PCC, System Memory, System IO, or Functional Fixed Hardware. commit b7898fda5bc7 ("cpufreq: Support for fast frequency switching") fast_switching is 'for switching CPU frequencies from interrupt context'. Writes to SystemMemory and SystemIo are fast and suitable this. This is not the case for PCC and might not be the case for FFH. Enable fast_switching for the cppc_cpufreq driver in above cases. Add cppc_allow_fast_switch() to check the desired performance register address space and set fast_switching accordingly. Signed-off-by: Pierre Gondois Reviewed-by: Sudeep Holla Acked-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki

cpufreq: CPPC: Register EM based on efficiency class information

2022-05-06T19:01:17Z

Performance states and energy consumption values are not advertised in ACPI. In the GicC structure of the MADT table, the "Processor Power Efficiency Class field" (called efficiency class from now) allows to describe the relative energy efficiency of CPUs. To leverage the EM and EAS, the CPPC driver creates a set of artificial performance states and registers them in the Energy Model (EM), such as: - Every 20 capacity unit, a performance state is created. - The energy cost of each performance state gradually increases. No power value is generated as only the cost is used in the EM. During task placement, a task can raise the frequency of its whole pd. This can make EAS place a task on a pd with CPUs that are individually less energy efficient. As cost values are artificial, and to place tasks on CPUs with the lower efficiency class, a gap in cost values is generated for adjacent efficiency classes. E.g.: - efficiency class = 0, capacity is in [0-1024], so cost values are in [0: 51] (one performance state every 20 capacity unit) - efficiency class = 1, capacity is in [0-1024], cost values are in [1*gap+0: 1*gap+51]. The value of the cost gap is chosen to absorb a the energy of 4 CPUs at their maximum capacity. This means that between: 1- a pd of 4 CPUs, each of them being used at almost their full capacity. Their efficiency class is N. 2- a CPU using almost none of its capacity. Its efficiency class is N+1 EAS will choose the first option. This patch also populates the (struct cpufreq_driver).register_em callback if the valid efficiency_class ACPI values are provided. Signed-off-by: Pierre Gondois Acked-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki

cpufreq: CPPC: Add per_cpu efficiency_class

2022-05-06T19:01:17Z

In ACPI, describing power efficiency of CPUs can be done through the following arm specific field: ACPI 6.4, s5.2.12.14 'GIC CPU Interface (GICC) Structure', 'Processor Power Efficiency Class field': Describes the relative power efficiency of the associated pro- cessor. Lower efficiency class numbers are more efficient than higher ones (e.g. efficiency class 0 should be treated as more efficient than efficiency class 1). However, absolute values of this number have no meaning: 2 isn’t necessarily half as efficient as 1. The efficiency_class field is stored in the GicC structure of the ACPI MADT table and it's currently supported in Linux for arm64 only. Thus, this new functionality is introduced for arm64 only. To allow the cppc_cpufreq driver to know and preprocess the efficiency_class values of all the CPUs, add a per_cpu efficiency_class variable to store them. At least 2 different efficiency classes must be present, otherwise there is no use in creating an Energy Model. The efficiency_class values are squeezed in [0:#efficiency_class-1] while conserving the order. For instance, efficiency classes of: [111, 212, 250] will be mapped to: [0 (was 111), 1 (was 212), 2 (was 250)]. Each policy being independently registered in the driver, populating the per_cpu efficiency_class is done only once at the driver initialization. This prevents from having each policy re-searching the efficiency_class values of other CPUs. The EM will be registered in a following patch. The patch also exports acpi_cpu_get_madt_gicc() to fetch the GicC structure of the ACPI MADT table for each CPU. Acked-by: Catalin Marinas Signed-off-by: Pierre Gondois Acked-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki

cpufreq: CPPC: Fix performance/frequency conversion

2022-02-10T05:26:52Z

CPUfreq governors request CPU frequencies using information on current CPU usage. The CPPC driver converts them to performance requests. Frequency targets are computed as: target_freq = (util / cpu_capacity) * max_freq target_freq is then clamped between [policy->min, policy->max]. The CPPC driver converts performance values to frequencies (and vice-versa) using cppc_cpufreq_perf_to_khz() and cppc_cpufreq_khz_to_perf(). These functions both use two different factors depending on the range of the input value. For cppc_cpufreq_khz_to_perf(): - (NOMINAL_PERF / NOMINAL_FREQ) or - (LOWEST_PERF / LOWEST_FREQ) and for cppc_cpufreq_perf_to_khz(): - (NOMINAL_FREQ / NOMINAL_PERF) or - ((NOMINAL_PERF - LOWEST_FREQ) / (NOMINAL_PERF - LOWEST_PERF)) This means: 1- the functions are not inverse for some values: (perf_to_khz(khz_to_perf(x)) != x) 2- cppc_cpufreq_perf_to_khz(LOWEST_PERF) can sometimes give a different value from LOWEST_FREQ due to integer approximation 3- it is implied that performance and frequency are proportional (NOMINAL_FREQ / NOMINAL_PERF) == (LOWEST_PERF / LOWEST_FREQ) This patch changes the conversion functions to an affine function. This fixes the 3 points above. Suggested-by: Lukasz Luba Suggested-by: Morten Rasmussen Signed-off-by: Pierre Gondois Signed-off-by: Viresh Kumar

cpufreq: remove useless INIT_LIST_HEAD()

2021-10-04T06:57:44Z

list cpu_data_list has been inited staticly through LIST_HEAD, so there's no need to call another INIT_LIST_HEAD. Simply remove it from cppc_cpufreq_init. Signed-off-by: Han Wang Signed-off-by: Viresh Kumar

cpufreq: CPPC: Add support for frequency invariance

2021-07-01T02:02:14Z

The Frequency Invariance Engine (FIE) is providing a frequency scaling correction factor that helps achieve more accurate load-tracking. Normally, this scaling factor can be obtained directly with the help of the cpufreq drivers as they know the exact frequency the hardware is running at. But that isn't the case for CPPC cpufreq driver. Another way of obtaining that is using the arch specific counter support, which is already present in kernel, but that hardware is optional for platforms. This patch updates the CPPC driver to register itself with the topology core to provide its own implementation (cppc_scale_freq_tick()) of topology_scale_freq_tick() which gets called by the scheduler on every tick. Note that the arch specific counters have higher priority than CPPC counters, if available, though the CPPC driver doesn't need to have any special handling for that. On an invocation of cppc_scale_freq_tick(), we schedule an irq work (since we reach here from hard-irq context), which then schedules a normal work item and cppc_scale_freq_workfn() updates the per_cpu arch_freq_scale variable based on the counter updates since the last tick. To allow platforms to disable this CPPC counter-based frequency invariance support, this is all done under CONFIG_ACPI_CPPC_CPUFREQ_FIE, which is enabled by default. This also exports sched_setattr_nocheck() as the CPPC driver can be built as a module. Cc: linux-acpi@vger.kernel.org Tested-by: Vincent Guittot Reviewed-by: Ionela Voinescu Tested-by: Qian Cai Signed-off-by: Viresh Kumar

cpufreq: CPPC: Pass structure instance by reference

2021-07-01T02:02:09Z

Don't pass structure instance by value, pass it by reference instead. Tested-by: Vincent Guittot Reviewed-by: Ionela Voinescu Tested-by: Qian Cai Signed-off-by: Viresh Kumar