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CPPC defined in section 8.4.7 of ACPI 6.0 specification suggests "To amortize the cost of PCC transactions, OSPM should read or write all PCC registers via a single read or write command when possible" This patch enables opportunistic batching of frequency transition requests whenever the request happen to overlap in time. Currently the access to pcc is serialized by a spin lock which does not scale well as we increase the number of cores in the system. This patch improves the scalability by allowing the differnt CPU cores to update PCC subspace in parallel and by batching requests which will reduce the certain types of operation(checking command completion bit, ringing doorbell) by a significant margin. Profiling shows significant improvement in the overall effeciency to service freq. transition requests. With this patch we observe close to 30% of the frequency transition requests being batched with other requests while running apache bench on a ARM platform with 6 independent domains(or sets of related cpus). Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
136 lines
2.8 KiB
C
136 lines
2.8 KiB
C
/*
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* CPPC (Collaborative Processor Performance Control) methods used
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* by CPUfreq drivers.
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*
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* (C) Copyright 2014, 2015 Linaro Ltd.
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* Author: Ashwin Chaugule <ashwin.chaugule@linaro.org>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; version 2
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* of the License.
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*/
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#ifndef _CPPC_ACPI_H
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#define _CPPC_ACPI_H
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#include <linux/acpi.h>
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#include <linux/types.h>
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#include <acpi/pcc.h>
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#include <acpi/processor.h>
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/* Only support CPPCv2 for now. */
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#define CPPC_NUM_ENT 21
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#define CPPC_REV 2
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#define PCC_CMD_COMPLETE 1
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#define MAX_CPC_REG_ENT 19
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/* CPPC specific PCC commands. */
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#define CMD_READ 0
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#define CMD_WRITE 1
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/* Each register has the folowing format. */
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struct cpc_reg {
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u8 descriptor;
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u16 length;
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u8 space_id;
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u8 bit_width;
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u8 bit_offset;
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u8 access_width;
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u64 __iomem address;
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} __packed;
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/*
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* Each entry in the CPC table is either
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* of type ACPI_TYPE_BUFFER or
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* ACPI_TYPE_INTEGER.
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*/
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struct cpc_register_resource {
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acpi_object_type type;
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u64 __iomem *sys_mem_vaddr;
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union {
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struct cpc_reg reg;
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u64 int_value;
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} cpc_entry;
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};
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/* Container to hold the CPC details for each CPU */
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struct cpc_desc {
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int num_entries;
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int version;
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int cpu_id;
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int write_cmd_status;
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int write_cmd_id;
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struct cpc_register_resource cpc_regs[MAX_CPC_REG_ENT];
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struct acpi_psd_package domain_info;
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};
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/* These are indexes into the per-cpu cpc_regs[]. Order is important. */
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enum cppc_regs {
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HIGHEST_PERF,
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NOMINAL_PERF,
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LOW_NON_LINEAR_PERF,
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LOWEST_PERF,
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GUARANTEED_PERF,
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DESIRED_PERF,
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MIN_PERF,
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MAX_PERF,
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PERF_REDUC_TOLERANCE,
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TIME_WINDOW,
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CTR_WRAP_TIME,
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REFERENCE_CTR,
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DELIVERED_CTR,
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PERF_LIMITED,
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ENABLE,
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AUTO_SEL_ENABLE,
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AUTO_ACT_WINDOW,
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ENERGY_PERF,
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REFERENCE_PERF,
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};
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/*
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* Categorization of registers as described
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* in the ACPI v.5.1 spec.
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* XXX: Only filling up ones which are used by governors
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* today.
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*/
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struct cppc_perf_caps {
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u32 highest_perf;
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u32 nominal_perf;
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u32 reference_perf;
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u32 lowest_perf;
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};
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struct cppc_perf_ctrls {
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u32 max_perf;
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u32 min_perf;
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u32 desired_perf;
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};
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struct cppc_perf_fb_ctrs {
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u64 reference;
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u64 prev_reference;
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u64 delivered;
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u64 prev_delivered;
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};
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/* Per CPU container for runtime CPPC management. */
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struct cpudata {
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int cpu;
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struct cppc_perf_caps perf_caps;
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struct cppc_perf_ctrls perf_ctrls;
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struct cppc_perf_fb_ctrs perf_fb_ctrs;
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struct cpufreq_policy *cur_policy;
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unsigned int shared_type;
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cpumask_var_t shared_cpu_map;
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};
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extern int cppc_get_perf_ctrs(int cpu, struct cppc_perf_fb_ctrs *perf_fb_ctrs);
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extern int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls);
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extern int cppc_get_perf_caps(int cpu, struct cppc_perf_caps *caps);
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extern int acpi_get_psd_map(struct cpudata **);
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#endif /* _CPPC_ACPI_H*/
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