Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[cris-mirror.git] / drivers / acpi / cppc_acpi.c

/*
 * CPPC (Collaborative Processor Performance Control) methods used by CPUfreq drivers.
 *
 * (C) Copyright 2014, 2015 Linaro Ltd.
 * Author: Ashwin Chaugule <ashwin.chaugule@linaro.org>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; version 2
 * of the License.
 *
 * CPPC describes a few methods for controlling CPU performance using
 * information from a per CPU table called CPC. This table is described in
 * the ACPI v5.0+ specification. The table consists of a list of
 * registers which may be memory mapped or hardware registers and also may
 * include some static integer values.
 *
 * CPU performance is on an abstract continuous scale as against a discretized
 * P-state scale which is tied to CPU frequency only. In brief, the basic
 * operation involves:
 *
 * - OS makes a CPU performance request. (Can provide min and max bounds)
 *
 * - Platform (such as BMC) is free to optimize request within requested bounds
 *   depending on power/thermal budgets etc.
 *
 * - Platform conveys its decision back to OS
 *
 * The communication between OS and platform occurs through another medium
 * called (PCC) Platform Communication Channel. This is a generic mailbox like
 * mechanism which includes doorbell semantics to indicate register updates.
 * See drivers/mailbox/pcc.c for details on PCC.
 *
 * Finer details about the PCC and CPPC spec are available in the ACPI v5.1 and
 * above specifications.
 */

#define pr_fmt(fmt)     "ACPI CPPC: " fmt

#include <linux/cpufreq.h>
#include <linux/delay.h>
#include <linux/ktime.h>

#include <acpi/cppc_acpi.h>
/*
 * Lock to provide mutually exclusive access to the PCC
 * channel. e.g. When the remote updates the shared region
 * with new data, the reader needs to be protected from
 * other CPUs activity on the same channel.
 */
static DEFINE_SPINLOCK(pcc_lock);

/*
 * The cpc_desc structure contains the ACPI register details
 * as described in the per CPU _CPC tables. The details
 * include the type of register (e.g. PCC, System IO, FFH etc.)
 * and destination addresses which lets us READ/WRITE CPU performance
 * information using the appropriate I/O methods.
 */
static DEFINE_PER_CPU(struct cpc_desc *, cpc_desc_ptr);

/* This layer handles all the PCC specifics for CPPC. */
static struct mbox_chan *pcc_channel;
static void __iomem *pcc_comm_addr;
static u64 comm_base_addr;
static int pcc_subspace_idx = -1;
static bool pcc_channel_acquired;
static ktime_t deadline;
static unsigned int pcc_mpar, pcc_mrtt;

/* pcc mapped address + header size + offset within PCC subspace */
#define GET_PCC_VADDR(offs) (pcc_comm_addr + 0x8 + (offs))

/*
 * Arbitrary Retries in case the remote processor is slow to respond
 * to PCC commands. Keeping it high enough to cover emulators where
 * the processors run painfully slow.
 */
#define NUM_RETRIES 500

static int check_pcc_chan(void)
{
        int ret = -EIO;
        struct acpi_pcct_shared_memory __iomem *generic_comm_base = pcc_comm_addr;
        ktime_t next_deadline = ktime_add(ktime_get(), deadline);

        /* Retry in case the remote processor was too slow to catch up. */
        while (!ktime_after(ktime_get(), next_deadline)) {
                /*
                 * Per spec, prior to boot the PCC space wil be initialized by
                 * platform and should have set the command completion bit when
                 * PCC can be used by OSPM
                 */
                if (readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE) {
                        ret = 0;
                        break;
                }
                /*
                 * Reducing the bus traffic in case this loop takes longer than
                 * a few retries.
                 */
                udelay(3);
        }

        return ret;
}

static int send_pcc_cmd(u16 cmd)
{
        int ret = -EIO;
        struct acpi_pcct_shared_memory *generic_comm_base =
                (struct acpi_pcct_shared_memory *) pcc_comm_addr;
        static ktime_t last_cmd_cmpl_time, last_mpar_reset;
        static int mpar_count;
        unsigned int time_delta;

        /*
         * For CMD_WRITE we know for a fact the caller should have checked
         * the channel before writing to PCC space
         */
        if (cmd == CMD_READ) {
                ret = check_pcc_chan();
                if (ret)
                        return ret;
        }

        /*
         * Handle the Minimum Request Turnaround Time(MRTT)
         * "The minimum amount of time that OSPM must wait after the completion
         * of a command before issuing the next command, in microseconds"
         */
        if (pcc_mrtt) {
                time_delta = ktime_us_delta(ktime_get(), last_cmd_cmpl_time);
                if (pcc_mrtt > time_delta)
                        udelay(pcc_mrtt - time_delta);
        }

        /*
         * Handle the non-zero Maximum Periodic Access Rate(MPAR)
         * "The maximum number of periodic requests that the subspace channel can
         * support, reported in commands per minute. 0 indicates no limitation."
         *
         * This parameter should be ideally zero or large enough so that it can
         * handle maximum number of requests that all the cores in the system can
         * collectively generate. If it is not, we will follow the spec and just
         * not send the request to the platform after hitting the MPAR limit in
         * any 60s window
         */
        if (pcc_mpar) {
                if (mpar_count == 0) {
                        time_delta = ktime_ms_delta(ktime_get(), last_mpar_reset);
                        if (time_delta < 60 * MSEC_PER_SEC) {
                                pr_debug("PCC cmd not sent due to MPAR limit");
                                return -EIO;
                        }
                        last_mpar_reset = ktime_get();
                        mpar_count = pcc_mpar;
                }
                mpar_count--;
        }

        /* Write to the shared comm region. */
        writew_relaxed(cmd, &generic_comm_base->command);

        /* Flip CMD COMPLETE bit */
        writew_relaxed(0, &generic_comm_base->status);

        /* Ring doorbell */
        ret = mbox_send_message(pcc_channel, &cmd);
        if (ret < 0) {
                pr_err("Err sending PCC mbox message. cmd:%d, ret:%d\n",
                                cmd, ret);
                return ret;
        }

        /*
         * For READs we need to ensure the cmd completed to ensure
         * the ensuing read()s can proceed. For WRITEs we dont care
         * because the actual write()s are done before coming here
         * and the next READ or WRITE will check if the channel
         * is busy/free at the entry of this call.
         *
         * If Minimum Request Turnaround Time is non-zero, we need
         * to record the completion time of both READ and WRITE
         * command for proper handling of MRTT, so we need to check
         * for pcc_mrtt in addition to CMD_READ
         */
        if (cmd == CMD_READ || pcc_mrtt) {
                ret = check_pcc_chan();
                if (pcc_mrtt)
                        last_cmd_cmpl_time = ktime_get();
        }

        mbox_client_txdone(pcc_channel, ret);
        return ret;
}

static void cppc_chan_tx_done(struct mbox_client *cl, void *msg, int ret)
{
        if (ret < 0)
                pr_debug("TX did not complete: CMD sent:%x, ret:%d\n",
                                *(u16 *)msg, ret);
        else
                pr_debug("TX completed. CMD sent:%x, ret:%d\n",
                                *(u16 *)msg, ret);
}

struct mbox_client cppc_mbox_cl = {
        .tx_done = cppc_chan_tx_done,
        .knows_txdone = true,
};

static int acpi_get_psd(struct cpc_desc *cpc_ptr, acpi_handle handle)
{
        int result = -EFAULT;
        acpi_status status = AE_OK;
        struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
        struct acpi_buffer format = {sizeof("NNNNN"), "NNNNN"};
        struct acpi_buffer state = {0, NULL};
        union acpi_object  *psd = NULL;
        struct acpi_psd_package *pdomain;

        status = acpi_evaluate_object_typed(handle, "_PSD", NULL, &buffer,
                        ACPI_TYPE_PACKAGE);
        if (ACPI_FAILURE(status))
                return -ENODEV;

        psd = buffer.pointer;
        if (!psd || psd->package.count != 1) {
                pr_debug("Invalid _PSD data\n");
                goto end;
        }

        pdomain = &(cpc_ptr->domain_info);

        state.length = sizeof(struct acpi_psd_package);
        state.pointer = pdomain;

        status = acpi_extract_package(&(psd->package.elements[0]),
                &format, &state);
        if (ACPI_FAILURE(status)) {
                pr_debug("Invalid _PSD data for CPU:%d\n", cpc_ptr->cpu_id);
                goto end;
        }

        if (pdomain->num_entries != ACPI_PSD_REV0_ENTRIES) {
                pr_debug("Unknown _PSD:num_entries for CPU:%d\n", cpc_ptr->cpu_id);
                goto end;
        }

        if (pdomain->revision != ACPI_PSD_REV0_REVISION) {
                pr_debug("Unknown _PSD:revision for CPU: %d\n", cpc_ptr->cpu_id);
                goto end;
        }

        if (pdomain->coord_type != DOMAIN_COORD_TYPE_SW_ALL &&
            pdomain->coord_type != DOMAIN_COORD_TYPE_SW_ANY &&
            pdomain->coord_type != DOMAIN_COORD_TYPE_HW_ALL) {
                pr_debug("Invalid _PSD:coord_type for CPU:%d\n", cpc_ptr->cpu_id);
                goto end;
        }

        result = 0;
end:
        kfree(buffer.pointer);
        return result;
}

/**
 * acpi_get_psd_map - Map the CPUs in a common freq domain.
 * @all_cpu_data: Ptrs to CPU specific CPPC data including PSD info.
 *
 *      Return: 0 for success or negative value for err.
 */
int acpi_get_psd_map(struct cpudata **all_cpu_data)
{
        int count_target;
        int retval = 0;
        unsigned int i, j;
        cpumask_var_t covered_cpus;
        struct cpudata *pr, *match_pr;
        struct acpi_psd_package *pdomain;
        struct acpi_psd_package *match_pdomain;
        struct cpc_desc *cpc_ptr, *match_cpc_ptr;

        if (!zalloc_cpumask_var(&covered_cpus, GFP_KERNEL))
                return -ENOMEM;

        /*
         * Now that we have _PSD data from all CPUs, lets setup P-state
         * domain info.
         */
        for_each_possible_cpu(i) {
                pr = all_cpu_data[i];
                if (!pr)
                        continue;

                if (cpumask_test_cpu(i, covered_cpus))
                        continue;

                cpc_ptr = per_cpu(cpc_desc_ptr, i);
                if (!cpc_ptr) {
                        retval = -EFAULT;
                        goto err_ret;
                }

                pdomain = &(cpc_ptr->domain_info);
                cpumask_set_cpu(i, pr->shared_cpu_map);
                cpumask_set_cpu(i, covered_cpus);
                if (pdomain->num_processors <= 1)
                        continue;

                /* Validate the Domain info */
                count_target = pdomain->num_processors;
                if (pdomain->coord_type == DOMAIN_COORD_TYPE_SW_ALL)
                        pr->shared_type = CPUFREQ_SHARED_TYPE_ALL;
                else if (pdomain->coord_type == DOMAIN_COORD_TYPE_HW_ALL)
                        pr->shared_type = CPUFREQ_SHARED_TYPE_HW;
                else if (pdomain->coord_type == DOMAIN_COORD_TYPE_SW_ANY)
                        pr->shared_type = CPUFREQ_SHARED_TYPE_ANY;

                for_each_possible_cpu(j) {
                        if (i == j)
                                continue;

                        match_cpc_ptr = per_cpu(cpc_desc_ptr, j);
                        if (!match_cpc_ptr) {
                                retval = -EFAULT;
                                goto err_ret;
                        }

                        match_pdomain = &(match_cpc_ptr->domain_info);
                        if (match_pdomain->domain != pdomain->domain)
                                continue;

                        /* Here i and j are in the same domain */
                        if (match_pdomain->num_processors != count_target) {
                                retval = -EFAULT;
                                goto err_ret;
                        }

                        if (pdomain->coord_type != match_pdomain->coord_type) {
                                retval = -EFAULT;
                                goto err_ret;
                        }

                        cpumask_set_cpu(j, covered_cpus);
                        cpumask_set_cpu(j, pr->shared_cpu_map);
                }

                for_each_possible_cpu(j) {
                        if (i == j)
                                continue;

                        match_pr = all_cpu_data[j];
                        if (!match_pr)
                                continue;

                        match_cpc_ptr = per_cpu(cpc_desc_ptr, j);
                        if (!match_cpc_ptr) {
                                retval = -EFAULT;
                                goto err_ret;
                        }

                        match_pdomain = &(match_cpc_ptr->domain_info);
                        if (match_pdomain->domain != pdomain->domain)
                                continue;

                        match_pr->shared_type = pr->shared_type;
                        cpumask_copy(match_pr->shared_cpu_map,
                                     pr->shared_cpu_map);
                }
        }

err_ret:
        for_each_possible_cpu(i) {
                pr = all_cpu_data[i];
                if (!pr)
                        continue;

                /* Assume no coordination on any error parsing domain info */
                if (retval) {
                        cpumask_clear(pr->shared_cpu_map);
                        cpumask_set_cpu(i, pr->shared_cpu_map);
                        pr->shared_type = CPUFREQ_SHARED_TYPE_ALL;
                }
        }

        free_cpumask_var(covered_cpus);
        return retval;
}
EXPORT_SYMBOL_GPL(acpi_get_psd_map);

static int register_pcc_channel(int pcc_subspace_idx)
{
        struct acpi_pcct_hw_reduced *cppc_ss;
        unsigned int len;
        u64 usecs_lat;

        if (pcc_subspace_idx >= 0) {
                pcc_channel = pcc_mbox_request_channel(&cppc_mbox_cl,
                                pcc_subspace_idx);

                if (IS_ERR(pcc_channel)) {
                        pr_err("Failed to find PCC communication channel\n");
                        return -ENODEV;
                }

                /*
                 * The PCC mailbox controller driver should
                 * have parsed the PCCT (global table of all
                 * PCC channels) and stored pointers to the
                 * subspace communication region in con_priv.
                 */
                cppc_ss = pcc_channel->con_priv;

                if (!cppc_ss) {
                        pr_err("No PCC subspace found for CPPC\n");
                        return -ENODEV;
                }

                /*
                 * This is the shared communication region
                 * for the OS and Platform to communicate over.
                 */
                comm_base_addr = cppc_ss->base_address;
                len = cppc_ss->length;

                /*
                 * cppc_ss->latency is just a Nominal value. In reality
                 * the remote processor could be much slower to reply.
                 * So add an arbitrary amount of wait on top of Nominal.
                 */
                usecs_lat = NUM_RETRIES * cppc_ss->latency;
                deadline = ns_to_ktime(usecs_lat * NSEC_PER_USEC);
                pcc_mrtt = cppc_ss->min_turnaround_time;
                pcc_mpar = cppc_ss->max_access_rate;

                pcc_comm_addr = acpi_os_ioremap(comm_base_addr, len);
                if (!pcc_comm_addr) {
                        pr_err("Failed to ioremap PCC comm region mem\n");
                        return -ENOMEM;
                }

                /* Set flag so that we dont come here for each CPU. */
                pcc_channel_acquired = true;
        }

        return 0;
}

/*
 * An example CPC table looks like the following.
 *
 *      Name(_CPC, Package()
 *                      {
 *                      17,
 *                      NumEntries
 *                      1,
 *                      // Revision
 *                      ResourceTemplate(){Register(PCC, 32, 0, 0x120, 2)},
 *                      // Highest Performance
 *                      ResourceTemplate(){Register(PCC, 32, 0, 0x124, 2)},
 *                      // Nominal Performance
 *                      ResourceTemplate(){Register(PCC, 32, 0, 0x128, 2)},
 *                      // Lowest Nonlinear Performance
 *                      ResourceTemplate(){Register(PCC, 32, 0, 0x12C, 2)},
 *                      // Lowest Performance
 *                      ResourceTemplate(){Register(PCC, 32, 0, 0x130, 2)},
 *                      // Guaranteed Performance Register
 *                      ResourceTemplate(){Register(PCC, 32, 0, 0x110, 2)},
 *                      // Desired Performance Register
 *                      ResourceTemplate(){Register(SystemMemory, 0, 0, 0, 0)},
 *                      ..
 *                      ..
 *                      ..
 *
 *              }
 * Each Register() encodes how to access that specific register.
 * e.g. a sample PCC entry has the following encoding:
 *
 *      Register (
 *              PCC,
 *              AddressSpaceKeyword
 *              8,
 *              //RegisterBitWidth
 *              8,
 *              //RegisterBitOffset
 *              0x30,
 *              //RegisterAddress
 *              9
 *              //AccessSize (subspace ID)
 *              0
 *              )
 *      }
 */

/**
 * acpi_cppc_processor_probe - Search for per CPU _CPC objects.
 * @pr: Ptr to acpi_processor containing this CPUs logical Id.
 *
 *      Return: 0 for success or negative value for err.
 */
int acpi_cppc_processor_probe(struct acpi_processor *pr)
{
        struct acpi_buffer output = {ACPI_ALLOCATE_BUFFER, NULL};
        union acpi_object *out_obj, *cpc_obj;
        struct cpc_desc *cpc_ptr;
        struct cpc_reg *gas_t;
        acpi_handle handle = pr->handle;
        unsigned int num_ent, i, cpc_rev;
        acpi_status status;
        int ret = -EFAULT;

        /* Parse the ACPI _CPC table for this cpu. */
        status = acpi_evaluate_object_typed(handle, "_CPC", NULL, &output,
                        ACPI_TYPE_PACKAGE);
        if (ACPI_FAILURE(status)) {
                ret = -ENODEV;
                goto out_buf_free;
        }

        out_obj = (union acpi_object *) output.pointer;

        cpc_ptr = kzalloc(sizeof(struct cpc_desc), GFP_KERNEL);
        if (!cpc_ptr) {
                ret = -ENOMEM;
                goto out_buf_free;
        }

        /* First entry is NumEntries. */
        cpc_obj = &out_obj->package.elements[0];
        if (cpc_obj->type == ACPI_TYPE_INTEGER) {
                num_ent = cpc_obj->integer.value;
        } else {
                pr_debug("Unexpected entry type(%d) for NumEntries\n",
                                cpc_obj->type);
                goto out_free;
        }

        /* Only support CPPCv2. Bail otherwise. */
        if (num_ent != CPPC_NUM_ENT) {
                pr_debug("Firmware exports %d entries. Expected: %d\n",
                                num_ent, CPPC_NUM_ENT);
                goto out_free;
        }

        /* Second entry should be revision. */
        cpc_obj = &out_obj->package.elements[1];
        if (cpc_obj->type == ACPI_TYPE_INTEGER) {
                cpc_rev = cpc_obj->integer.value;
        } else {
                pr_debug("Unexpected entry type(%d) for Revision\n",
                                cpc_obj->type);
                goto out_free;
        }

        if (cpc_rev != CPPC_REV) {
                pr_debug("Firmware exports revision:%d. Expected:%d\n",
                                cpc_rev, CPPC_REV);
                goto out_free;
        }

        /* Iterate through remaining entries in _CPC */
        for (i = 2; i < num_ent; i++) {
                cpc_obj = &out_obj->package.elements[i];

                if (cpc_obj->type == ACPI_TYPE_INTEGER) {
                        cpc_ptr->cpc_regs[i-2].type = ACPI_TYPE_INTEGER;
                        cpc_ptr->cpc_regs[i-2].cpc_entry.int_value = cpc_obj->integer.value;
                } else if (cpc_obj->type == ACPI_TYPE_BUFFER) {
                        gas_t = (struct cpc_reg *)
                                cpc_obj->buffer.pointer;

                        /*
                         * The PCC Subspace index is encoded inside
                         * the CPC table entries. The same PCC index
                         * will be used for all the PCC entries,
                         * so extract it only once.
                         */
                        if (gas_t->space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {
                                if (pcc_subspace_idx < 0)
                                        pcc_subspace_idx = gas_t->access_width;
                                else if (pcc_subspace_idx != gas_t->access_width) {
                                        pr_debug("Mismatched PCC ids.\n");
                                        goto out_free;
                                }
                        } else if (gas_t->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY) {
                                /* Support only PCC and SYS MEM type regs */
                                pr_debug("Unsupported register type: %d\n", gas_t->space_id);
                                goto out_free;
                        }

                        cpc_ptr->cpc_regs[i-2].type = ACPI_TYPE_BUFFER;
                        memcpy(&cpc_ptr->cpc_regs[i-2].cpc_entry.reg, gas_t, sizeof(*gas_t));
                } else {
                        pr_debug("Err in entry:%d in CPC table of CPU:%d \n", i, pr->id);
                        goto out_free;
                }
        }
        /* Store CPU Logical ID */
        cpc_ptr->cpu_id = pr->id;

        /* Parse PSD data for this CPU */
        ret = acpi_get_psd(cpc_ptr, handle);
        if (ret)
                goto out_free;

        /* Register PCC channel once for all CPUs. */
        if (!pcc_channel_acquired) {
                ret = register_pcc_channel(pcc_subspace_idx);
                if (ret)
                        goto out_free;
        }

        /* Plug PSD data into this CPUs CPC descriptor. */
        per_cpu(cpc_desc_ptr, pr->id) = cpc_ptr;

        /* Everything looks okay */
        pr_debug("Parsed CPC struct for CPU: %d\n", pr->id);

        kfree(output.pointer);
        return 0;

out_free:
        kfree(cpc_ptr);

out_buf_free:
        kfree(output.pointer);
        return ret;
}
EXPORT_SYMBOL_GPL(acpi_cppc_processor_probe);

/**
 * acpi_cppc_processor_exit - Cleanup CPC structs.
 * @pr: Ptr to acpi_processor containing this CPUs logical Id.
 *
 * Return: Void
 */
void acpi_cppc_processor_exit(struct acpi_processor *pr)
{
        struct cpc_desc *cpc_ptr;
        cpc_ptr = per_cpu(cpc_desc_ptr, pr->id);
        kfree(cpc_ptr);
}
EXPORT_SYMBOL_GPL(acpi_cppc_processor_exit);

/*
 * Since cpc_read and cpc_write are called while holding pcc_lock, it should be
 * as fast as possible. We have already mapped the PCC subspace during init, so
 * we can directly write to it.
 */

static int cpc_read(struct cpc_reg *reg, u64 *val)
{
        int ret_val = 0;

        *val = 0;
        if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {
                void __iomem *vaddr = GET_PCC_VADDR(reg->address);

                switch (reg->bit_width) {
                case 8:
                        *val = readb_relaxed(vaddr);
                        break;
                case 16:
                        *val = readw_relaxed(vaddr);
                        break;
                case 32:
                        *val = readl_relaxed(vaddr);
                        break;
                case 64:
                        *val = readq_relaxed(vaddr);
                        break;
                default:
                        pr_debug("Error: Cannot read %u bit width from PCC\n",
                                reg->bit_width);
                        ret_val = -EFAULT;
                }
        } else
                ret_val = acpi_os_read_memory((acpi_physical_address)reg->address,
                                        val, reg->bit_width);
        return ret_val;
}

static int cpc_write(struct cpc_reg *reg, u64 val)
{
        int ret_val = 0;

        if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {
                void __iomem *vaddr = GET_PCC_VADDR(reg->address);

                switch (reg->bit_width) {
                case 8:
                        writeb_relaxed(val, vaddr);
                        break;
                case 16:
                        writew_relaxed(val, vaddr);
                        break;
                case 32:
                        writel_relaxed(val, vaddr);
                        break;
                case 64:
                        writeq_relaxed(val, vaddr);
                        break;
                default:
                        pr_debug("Error: Cannot write %u bit width to PCC\n",
                                reg->bit_width);
                        ret_val = -EFAULT;
                        break;
                }
        } else
                ret_val = acpi_os_write_memory((acpi_physical_address)reg->address,
                                val, reg->bit_width);
        return ret_val;
}

/**
 * cppc_get_perf_caps - Get a CPUs performance capabilities.
 * @cpunum: CPU from which to get capabilities info.
 * @perf_caps: ptr to cppc_perf_caps. See cppc_acpi.h
 *
 * Return: 0 for success with perf_caps populated else -ERRNO.
 */
int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
{
        struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpunum);
        struct cpc_register_resource *highest_reg, *lowest_reg, *ref_perf,
                                                                 *nom_perf;
        u64 high, low, ref, nom;
        int ret = 0;

        if (!cpc_desc) {
                pr_debug("No CPC descriptor for CPU:%d\n", cpunum);
                return -ENODEV;
        }

        highest_reg = &cpc_desc->cpc_regs[HIGHEST_PERF];
        lowest_reg = &cpc_desc->cpc_regs[LOWEST_PERF];
        ref_perf = &cpc_desc->cpc_regs[REFERENCE_PERF];
        nom_perf = &cpc_desc->cpc_regs[NOMINAL_PERF];

        spin_lock(&pcc_lock);

        /* Are any of the regs PCC ?*/
        if ((highest_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) ||
                        (lowest_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) ||
                        (ref_perf->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) ||
                        (nom_perf->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM)) {
                /* Ring doorbell once to update PCC subspace */
                if (send_pcc_cmd(CMD_READ) < 0) {
                        ret = -EIO;
                        goto out_err;
                }
        }

        cpc_read(&highest_reg->cpc_entry.reg, &high);
        perf_caps->highest_perf = high;

        cpc_read(&lowest_reg->cpc_entry.reg, &low);
        perf_caps->lowest_perf = low;

        cpc_read(&ref_perf->cpc_entry.reg, &ref);
        perf_caps->reference_perf = ref;

        cpc_read(&nom_perf->cpc_entry.reg, &nom);
        perf_caps->nominal_perf = nom;

        if (!ref)
                perf_caps->reference_perf = perf_caps->nominal_perf;

        if (!high || !low || !nom)
                ret = -EFAULT;

out_err:
        spin_unlock(&pcc_lock);
        return ret;
}
EXPORT_SYMBOL_GPL(cppc_get_perf_caps);

/**
 * cppc_get_perf_ctrs - Read a CPUs performance feedback counters.
 * @cpunum: CPU from which to read counters.
 * @perf_fb_ctrs: ptr to cppc_perf_fb_ctrs. See cppc_acpi.h
 *
 * Return: 0 for success with perf_fb_ctrs populated else -ERRNO.
 */
int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs)
{
        struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpunum);
        struct cpc_register_resource *delivered_reg, *reference_reg;
        u64 delivered, reference;
        int ret = 0;

        if (!cpc_desc) {
                pr_debug("No CPC descriptor for CPU:%d\n", cpunum);
                return -ENODEV;
        }

        delivered_reg = &cpc_desc->cpc_regs[DELIVERED_CTR];
        reference_reg = &cpc_desc->cpc_regs[REFERENCE_CTR];

        spin_lock(&pcc_lock);

        /* Are any of the regs PCC ?*/
        if ((delivered_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) ||
                        (reference_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM)) {
                /* Ring doorbell once to update PCC subspace */
                if (send_pcc_cmd(CMD_READ) < 0) {
                        ret = -EIO;
                        goto out_err;
                }
        }

        cpc_read(&delivered_reg->cpc_entry.reg, &delivered);
        cpc_read(&reference_reg->cpc_entry.reg, &reference);

        if (!delivered || !reference) {
                ret = -EFAULT;
                goto out_err;
        }

        perf_fb_ctrs->delivered = delivered;
        perf_fb_ctrs->reference = reference;

        perf_fb_ctrs->delivered -= perf_fb_ctrs->prev_delivered;
        perf_fb_ctrs->reference -= perf_fb_ctrs->prev_reference;

        perf_fb_ctrs->prev_delivered = delivered;
        perf_fb_ctrs->prev_reference = reference;

out_err:
        spin_unlock(&pcc_lock);
        return ret;
}
EXPORT_SYMBOL_GPL(cppc_get_perf_ctrs);

/**
 * cppc_set_perf - Set a CPUs performance controls.
 * @cpu: CPU for which to set performance controls.
 * @perf_ctrls: ptr to cppc_perf_ctrls. See cppc_acpi.h
 *
 * Return: 0 for success, -ERRNO otherwise.
 */
int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
{
        struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
        struct cpc_register_resource *desired_reg;
        int ret = 0;

        if (!cpc_desc) {
                pr_debug("No CPC descriptor for CPU:%d\n", cpu);
                return -ENODEV;
        }

        desired_reg = &cpc_desc->cpc_regs[DESIRED_PERF];

        spin_lock(&pcc_lock);

        /* If this is PCC reg, check if channel is free before writing */
        if (desired_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {
                ret = check_pcc_chan();
                if (ret)
                        goto busy_channel;
        }

        /*
         * Skip writing MIN/MAX until Linux knows how to come up with
         * useful values.
         */
        cpc_write(&desired_reg->cpc_entry.reg, perf_ctrls->desired_perf);

        /* Is this a PCC reg ?*/
        if (desired_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {
                /* Ring doorbell so Remote can get our perf request. */
                if (send_pcc_cmd(CMD_WRITE) < 0)
                        ret = -EIO;
        }
busy_channel:
        spin_unlock(&pcc_lock);

        return ret;
}
EXPORT_SYMBOL_GPL(cppc_set_perf);