iio: ep93xx: remove redundant return value check of platform_get_resource()

[linux-2.6/btrfs-unstable.git] / drivers / hwmon / xgene-hwmon.c

/*
 * APM X-Gene SoC Hardware Monitoring Driver
 *
 * Copyright (c) 2016, Applied Micro Circuits Corporation
 * Author: Loc Ho <lho@apm.com>
 *         Hoan Tran <hotran@apm.com>
 *
 * 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; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 *
 * This driver provides the following features:
 *  - Retrieve CPU total power (uW)
 *  - Retrieve IO total power (uW)
 *  - Retrieve SoC temperature (milli-degree C) and alarm
 */
#include <linux/acpi.h>
#include <linux/dma-mapping.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/io.h>
#include <linux/interrupt.h>
#include <linux/kfifo.h>
#include <linux/mailbox_controller.h>
#include <linux/mailbox_client.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>

#include <acpi/pcc.h>

/* SLIMpro message defines */
#define MSG_TYPE_DBG                    0
#define MSG_TYPE_ERR                    7
#define MSG_TYPE_PWRMGMT                9

#define MSG_TYPE(v)                     (((v) & 0xF0000000) >> 28)
#define MSG_TYPE_SET(v)                 (((v) << 28) & 0xF0000000)
#define MSG_SUBTYPE(v)                  (((v) & 0x0F000000) >> 24)
#define MSG_SUBTYPE_SET(v)              (((v) << 24) & 0x0F000000)

#define DBG_SUBTYPE_SENSOR_READ         4
#define SENSOR_RD_MSG                   0x04FFE902
#define SENSOR_RD_EN_ADDR(a)            ((a) & 0x000FFFFF)
#define PMD_PWR_REG                     0x20
#define PMD_PWR_MW_REG                  0x26
#define SOC_PWR_REG                     0x21
#define SOC_PWR_MW_REG                  0x27
#define SOC_TEMP_REG                    0x10

#define TEMP_NEGATIVE_BIT               8
#define SENSOR_INVALID_DATA             BIT(15)

#define PWRMGMT_SUBTYPE_TPC             1
#define TPC_ALARM                       2
#define TPC_GET_ALARM                   3
#define TPC_CMD(v)                      (((v) & 0x00FF0000) >> 16)
#define TPC_CMD_SET(v)                  (((v) << 16) & 0x00FF0000)
#define TPC_EN_MSG(hndl, cmd, type) \
        (MSG_TYPE_SET(MSG_TYPE_PWRMGMT) | \
        MSG_SUBTYPE_SET(hndl) | TPC_CMD_SET(cmd) | type)

/* PCC defines */
#define PCC_SIGNATURE_MASK              0x50424300
#define PCCC_GENERATE_DB_INT            BIT(15)
#define PCCS_CMD_COMPLETE               BIT(0)
#define PCCS_SCI_DOORBEL                BIT(1)
#define PCCS_PLATFORM_NOTIFICATION      BIT(3)
/*
 * Arbitrary retries in case the remote processor is slow to respond
 * to PCC commands
 */
#define PCC_NUM_RETRIES                 500

#define ASYNC_MSG_FIFO_SIZE             16
#define MBOX_OP_TIMEOUTMS               1000

#define WATT_TO_mWATT(x)                ((x) * 1000)
#define mWATT_TO_uWATT(x)               ((x) * 1000)
#define CELSIUS_TO_mCELSIUS(x)          ((x) * 1000)

#define to_xgene_hwmon_dev(cl)          \
        container_of(cl, struct xgene_hwmon_dev, mbox_client)

enum xgene_hwmon_version {
        XGENE_HWMON_V1 = 0,
        XGENE_HWMON_V2 = 1,
};

struct slimpro_resp_msg {
        u32 msg;
        u32 param1;
        u32 param2;
} __packed;

struct xgene_hwmon_dev {
        struct device           *dev;
        struct mbox_chan        *mbox_chan;
        struct mbox_client      mbox_client;
        int                     mbox_idx;

        spinlock_t              kfifo_lock;
        struct mutex            rd_mutex;
        struct completion       rd_complete;
        int                     resp_pending;
        struct slimpro_resp_msg sync_msg;

        struct work_struct      workq;
        struct kfifo_rec_ptr_1  async_msg_fifo;

        struct device           *hwmon_dev;
        bool                    temp_critical_alarm;

        phys_addr_t             comm_base_addr;
        void                    *pcc_comm_addr;
        u64                     usecs_lat;
};

/*
 * This function tests and clears a bitmask then returns its old value
 */
static u16 xgene_word_tst_and_clr(u16 *addr, u16 mask)
{
        u16 ret, val;

        val = le16_to_cpu(READ_ONCE(*addr));
        ret = val & mask;
        val &= ~mask;
        WRITE_ONCE(*addr, cpu_to_le16(val));

        return ret;
}

static int xgene_hwmon_pcc_rd(struct xgene_hwmon_dev *ctx, u32 *msg)
{
        struct acpi_pcct_shared_memory *generic_comm_base = ctx->pcc_comm_addr;
        u32 *ptr = (void *)(generic_comm_base + 1);
        int rc, i;
        u16 val;

        mutex_lock(&ctx->rd_mutex);
        init_completion(&ctx->rd_complete);
        ctx->resp_pending = true;

        /* Write signature for subspace */
        WRITE_ONCE(generic_comm_base->signature,
                   cpu_to_le32(PCC_SIGNATURE_MASK | ctx->mbox_idx));

        /* Write to the shared command region */
        WRITE_ONCE(generic_comm_base->command,
                   cpu_to_le16(MSG_TYPE(msg[0]) | PCCC_GENERATE_DB_INT));

        /* Flip CMD COMPLETE bit */
        val = le16_to_cpu(READ_ONCE(generic_comm_base->status));
        val &= ~PCCS_CMD_COMPLETE;
        WRITE_ONCE(generic_comm_base->status, cpu_to_le16(val));

        /* Copy the message to the PCC comm space */
        for (i = 0; i < sizeof(struct slimpro_resp_msg) / 4; i++)
                WRITE_ONCE(ptr[i], cpu_to_le32(msg[i]));

        /* Ring the doorbell */
        rc = mbox_send_message(ctx->mbox_chan, msg);
        if (rc < 0) {
                dev_err(ctx->dev, "Mailbox send error %d\n", rc);
                goto err;
        }
        if (!wait_for_completion_timeout(&ctx->rd_complete,
                                         usecs_to_jiffies(ctx->usecs_lat))) {
                dev_err(ctx->dev, "Mailbox operation timed out\n");
                rc = -ETIMEDOUT;
                goto err;
        }

        /* Check for error message */
        if (MSG_TYPE(ctx->sync_msg.msg) == MSG_TYPE_ERR) {
                rc = -EINVAL;
                goto err;
        }

        msg[0] = ctx->sync_msg.msg;
        msg[1] = ctx->sync_msg.param1;
        msg[2] = ctx->sync_msg.param2;

err:
        mbox_chan_txdone(ctx->mbox_chan, 0);
        ctx->resp_pending = false;
        mutex_unlock(&ctx->rd_mutex);
        return rc;
}

static int xgene_hwmon_rd(struct xgene_hwmon_dev *ctx, u32 *msg)
{
        int rc;

        mutex_lock(&ctx->rd_mutex);
        init_completion(&ctx->rd_complete);
        ctx->resp_pending = true;

        rc = mbox_send_message(ctx->mbox_chan, msg);
        if (rc < 0) {
                dev_err(ctx->dev, "Mailbox send error %d\n", rc);
                goto err;
        }

        if (!wait_for_completion_timeout(&ctx->rd_complete,
                                         msecs_to_jiffies(MBOX_OP_TIMEOUTMS))) {
                dev_err(ctx->dev, "Mailbox operation timed out\n");
                rc = -ETIMEDOUT;
                goto err;
        }

        /* Check for error message */
        if (MSG_TYPE(ctx->sync_msg.msg) == MSG_TYPE_ERR) {
                rc = -EINVAL;
                goto err;
        }

        msg[0] = ctx->sync_msg.msg;
        msg[1] = ctx->sync_msg.param1;
        msg[2] = ctx->sync_msg.param2;

err:
        ctx->resp_pending = false;
        mutex_unlock(&ctx->rd_mutex);
        return rc;
}

static int xgene_hwmon_reg_map_rd(struct xgene_hwmon_dev *ctx, u32 addr,
                                  u32 *data)
{
        u32 msg[3];
        int rc;

        msg[0] = SENSOR_RD_MSG;
        msg[1] = SENSOR_RD_EN_ADDR(addr);
        msg[2] = 0;

        if (acpi_disabled)
                rc = xgene_hwmon_rd(ctx, msg);
        else
                rc = xgene_hwmon_pcc_rd(ctx, msg);

        if (rc < 0)
                return rc;

        /*
         * Check if sensor data is valid.
         */
        if (msg[1] & SENSOR_INVALID_DATA)
                return -ENODATA;

        *data = msg[1];

        return rc;
}

static int xgene_hwmon_get_notification_msg(struct xgene_hwmon_dev *ctx,
                                            u32 *amsg)
{
        u32 msg[3];
        int rc;

        msg[0] = TPC_EN_MSG(PWRMGMT_SUBTYPE_TPC, TPC_GET_ALARM, 0);
        msg[1] = 0;
        msg[2] = 0;

        rc = xgene_hwmon_pcc_rd(ctx, msg);
        if (rc < 0)
                return rc;

        amsg[0] = msg[0];
        amsg[1] = msg[1];
        amsg[2] = msg[2];

        return rc;
}

static int xgene_hwmon_get_cpu_pwr(struct xgene_hwmon_dev *ctx, u32 *val)
{
        u32 watt, mwatt;
        int rc;

        rc = xgene_hwmon_reg_map_rd(ctx, PMD_PWR_REG, &watt);
        if (rc < 0)
                return rc;

        rc = xgene_hwmon_reg_map_rd(ctx, PMD_PWR_MW_REG, &mwatt);
        if (rc < 0)
                return rc;

        *val = WATT_TO_mWATT(watt) + mwatt;
        return 0;
}

static int xgene_hwmon_get_io_pwr(struct xgene_hwmon_dev *ctx, u32 *val)
{
        u32 watt, mwatt;
        int rc;

        rc = xgene_hwmon_reg_map_rd(ctx, SOC_PWR_REG, &watt);
        if (rc < 0)
                return rc;

        rc = xgene_hwmon_reg_map_rd(ctx, SOC_PWR_MW_REG, &mwatt);
        if (rc < 0)
                return rc;

        *val = WATT_TO_mWATT(watt) + mwatt;
        return 0;
}

static int xgene_hwmon_get_temp(struct xgene_hwmon_dev *ctx, u32 *val)
{
        return xgene_hwmon_reg_map_rd(ctx, SOC_TEMP_REG, val);
}

/*
 * Sensor temperature/power functions
 */
static ssize_t temp1_input_show(struct device *dev,
                                struct device_attribute *attr,
                                char *buf)
{
        struct xgene_hwmon_dev *ctx = dev_get_drvdata(dev);
        int rc, temp;
        u32 val;

        rc = xgene_hwmon_get_temp(ctx, &val);
        if (rc < 0)
                return rc;

        temp = sign_extend32(val, TEMP_NEGATIVE_BIT);

        return snprintf(buf, PAGE_SIZE, "%d\n", CELSIUS_TO_mCELSIUS(temp));
}

static ssize_t temp1_label_show(struct device *dev,
                                struct device_attribute *attr,
                                char *buf)
{
        return snprintf(buf, PAGE_SIZE, "SoC Temperature\n");
}

static ssize_t temp1_critical_alarm_show(struct device *dev,
                                         struct device_attribute *devattr,
                                         char *buf)
{
        struct xgene_hwmon_dev *ctx = dev_get_drvdata(dev);

        return snprintf(buf, PAGE_SIZE, "%d\n", ctx->temp_critical_alarm);
}

static ssize_t power1_label_show(struct device *dev,
                                 struct device_attribute *attr,
                                 char *buf)
{
        return snprintf(buf, PAGE_SIZE, "CPU power\n");
}

static ssize_t power2_label_show(struct device *dev,
                                 struct device_attribute *attr,
                                 char *buf)
{
        return snprintf(buf, PAGE_SIZE, "IO power\n");
}

static ssize_t power1_input_show(struct device *dev,
                                 struct device_attribute *attr,
                                 char *buf)
{
        struct xgene_hwmon_dev *ctx = dev_get_drvdata(dev);
        u32 val;
        int rc;

        rc = xgene_hwmon_get_cpu_pwr(ctx, &val);
        if (rc < 0)
                return rc;

        return snprintf(buf, PAGE_SIZE, "%u\n", mWATT_TO_uWATT(val));
}

static ssize_t power2_input_show(struct device *dev,
                                 struct device_attribute *attr,
                                 char *buf)
{
        struct xgene_hwmon_dev *ctx = dev_get_drvdata(dev);
        u32 val;
        int rc;

        rc = xgene_hwmon_get_io_pwr(ctx, &val);
        if (rc < 0)
                return rc;

        return snprintf(buf, PAGE_SIZE, "%u\n", mWATT_TO_uWATT(val));
}

static DEVICE_ATTR_RO(temp1_label);
static DEVICE_ATTR_RO(temp1_input);
static DEVICE_ATTR_RO(temp1_critical_alarm);
static DEVICE_ATTR_RO(power1_label);
static DEVICE_ATTR_RO(power1_input);
static DEVICE_ATTR_RO(power2_label);
static DEVICE_ATTR_RO(power2_input);

static struct attribute *xgene_hwmon_attrs[] = {
        &dev_attr_temp1_label.attr,
        &dev_attr_temp1_input.attr,
        &dev_attr_temp1_critical_alarm.attr,
        &dev_attr_power1_label.attr,
        &dev_attr_power1_input.attr,
        &dev_attr_power2_label.attr,
        &dev_attr_power2_input.attr,
        NULL,
};

ATTRIBUTE_GROUPS(xgene_hwmon);

static int xgene_hwmon_tpc_alarm(struct xgene_hwmon_dev *ctx,
                                 struct slimpro_resp_msg *amsg)
{
        ctx->temp_critical_alarm = !!amsg->param2;
        sysfs_notify(&ctx->dev->kobj, NULL, "temp1_critical_alarm");

        return 0;
}

static void xgene_hwmon_process_pwrmsg(struct xgene_hwmon_dev *ctx,
                                       struct slimpro_resp_msg *amsg)
{
        if ((MSG_SUBTYPE(amsg->msg) == PWRMGMT_SUBTYPE_TPC) &&
            (TPC_CMD(amsg->msg) == TPC_ALARM))
                xgene_hwmon_tpc_alarm(ctx, amsg);
}

/*
 * This function is called to process async work queue
 */
static void xgene_hwmon_evt_work(struct work_struct *work)
{
        struct slimpro_resp_msg amsg;
        struct xgene_hwmon_dev *ctx;
        int ret;

        ctx = container_of(work, struct xgene_hwmon_dev, workq);
        while (kfifo_out_spinlocked(&ctx->async_msg_fifo, &amsg,
                                    sizeof(struct slimpro_resp_msg),
                                    &ctx->kfifo_lock)) {
                /*
                 * If PCC, send a consumer command to Platform to get info
                 * If Slimpro Mailbox, get message from specific FIFO
                 */
                if (!acpi_disabled) {
                        ret = xgene_hwmon_get_notification_msg(ctx,
                                                               (u32 *)&amsg);
                        if (ret < 0)
                                continue;
                }

                if (MSG_TYPE(amsg.msg) == MSG_TYPE_PWRMGMT)
                        xgene_hwmon_process_pwrmsg(ctx, &amsg);
        }
}

static int xgene_hwmon_rx_ready(struct xgene_hwmon_dev *ctx, void *msg)
{
        if (IS_ERR_OR_NULL(ctx->hwmon_dev) && !ctx->resp_pending) {
                /* Enqueue to the FIFO */
                kfifo_in_spinlocked(&ctx->async_msg_fifo, msg,
                                    sizeof(struct slimpro_resp_msg),
                                    &ctx->kfifo_lock);
                return -ENODEV;
        }

        return 0;
}

/*
 * This function is called when the SLIMpro Mailbox received a message
 */
static void xgene_hwmon_rx_cb(struct mbox_client *cl, void *msg)
{
        struct xgene_hwmon_dev *ctx = to_xgene_hwmon_dev(cl);

        /*
         * While the driver registers with the mailbox framework, an interrupt
         * can be pending before the probe function completes its
         * initialization. If such condition occurs, just queue up the message
         * as the driver is not ready for servicing the callback.
         */
        if (xgene_hwmon_rx_ready(ctx, msg) < 0)
                return;

        /*
         * Response message format:
         * msg[0] is the return code of the operation
         * msg[1] is the first parameter word
         * msg[2] is the second parameter word
         *
         * As message only supports dword size, just assign it.
         */

        /* Check for sync query */
        if (ctx->resp_pending &&
            ((MSG_TYPE(((u32 *)msg)[0]) == MSG_TYPE_ERR) ||
             (MSG_TYPE(((u32 *)msg)[0]) == MSG_TYPE_DBG &&
              MSG_SUBTYPE(((u32 *)msg)[0]) == DBG_SUBTYPE_SENSOR_READ) ||
             (MSG_TYPE(((u32 *)msg)[0]) == MSG_TYPE_PWRMGMT &&
              MSG_SUBTYPE(((u32 *)msg)[0]) == PWRMGMT_SUBTYPE_TPC &&
              TPC_CMD(((u32 *)msg)[0]) == TPC_ALARM))) {
                ctx->sync_msg.msg = ((u32 *)msg)[0];
                ctx->sync_msg.param1 = ((u32 *)msg)[1];
                ctx->sync_msg.param2 = ((u32 *)msg)[2];

                /* Operation waiting for response */
                complete(&ctx->rd_complete);

                return;
        }

        /* Enqueue to the FIFO */
        kfifo_in_spinlocked(&ctx->async_msg_fifo, msg,
                            sizeof(struct slimpro_resp_msg), &ctx->kfifo_lock);
        /* Schedule the bottom handler */
        schedule_work(&ctx->workq);
}

/*
 * This function is called when the PCC Mailbox received a message
 */
static void xgene_hwmon_pcc_rx_cb(struct mbox_client *cl, void *msg)
{
        struct xgene_hwmon_dev *ctx = to_xgene_hwmon_dev(cl);
        struct acpi_pcct_shared_memory *generic_comm_base = ctx->pcc_comm_addr;
        struct slimpro_resp_msg amsg;

        /*
         * While the driver registers with the mailbox framework, an interrupt
         * can be pending before the probe function completes its
         * initialization. If such condition occurs, just queue up the message
         * as the driver is not ready for servicing the callback.
         */
        if (xgene_hwmon_rx_ready(ctx, &amsg) < 0)
                return;

        msg = generic_comm_base + 1;
        /* Check if platform sends interrupt */
        if (!xgene_word_tst_and_clr(&generic_comm_base->status,
                                    PCCS_SCI_DOORBEL))
                return;

        /*
         * Response message format:
         * msg[0] is the return code of the operation
         * msg[1] is the first parameter word
         * msg[2] is the second parameter word
         *
         * As message only supports dword size, just assign it.
         */

        /* Check for sync query */
        if (ctx->resp_pending &&
            ((MSG_TYPE(((u32 *)msg)[0]) == MSG_TYPE_ERR) ||
             (MSG_TYPE(((u32 *)msg)[0]) == MSG_TYPE_DBG &&
              MSG_SUBTYPE(((u32 *)msg)[0]) == DBG_SUBTYPE_SENSOR_READ) ||
             (MSG_TYPE(((u32 *)msg)[0]) == MSG_TYPE_PWRMGMT &&
              MSG_SUBTYPE(((u32 *)msg)[0]) == PWRMGMT_SUBTYPE_TPC &&
              TPC_CMD(((u32 *)msg)[0]) == TPC_ALARM))) {
                /* Check if platform completes command */
                if (xgene_word_tst_and_clr(&generic_comm_base->status,
                                           PCCS_CMD_COMPLETE)) {
                        ctx->sync_msg.msg = ((u32 *)msg)[0];
                        ctx->sync_msg.param1 = ((u32 *)msg)[1];
                        ctx->sync_msg.param2 = ((u32 *)msg)[2];

                        /* Operation waiting for response */
                        complete(&ctx->rd_complete);

                        return;
                }
        }

        /*
         * Platform notifies interrupt to OSPM.
         * OPSM schedules a consumer command to get this information
         * in a workqueue. Platform must wait until OSPM has issued
         * a consumer command that serves this notification.
         */

        /* Enqueue to the FIFO */
        kfifo_in_spinlocked(&ctx->async_msg_fifo, &amsg,
                            sizeof(struct slimpro_resp_msg), &ctx->kfifo_lock);
        /* Schedule the bottom handler */
        schedule_work(&ctx->workq);
}

static void xgene_hwmon_tx_done(struct mbox_client *cl, void *msg, int ret)
{
        if (ret) {
                dev_dbg(cl->dev, "TX did not complete: CMD sent:%x, ret:%d\n",
                        *(u16 *)msg, ret);
        } else {
                dev_dbg(cl->dev, "TX completed. CMD sent:%x, ret:%d\n",
                        *(u16 *)msg, ret);
        }
}

#ifdef CONFIG_ACPI
static const struct acpi_device_id xgene_hwmon_acpi_match[] = {
        {"APMC0D29", XGENE_HWMON_V1},
        {"APMC0D8A", XGENE_HWMON_V2},
        {},
};
MODULE_DEVICE_TABLE(acpi, xgene_hwmon_acpi_match);
#endif

static int xgene_hwmon_probe(struct platform_device *pdev)
{
        struct xgene_hwmon_dev *ctx;
        struct mbox_client *cl;
        int rc;

        ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
        if (!ctx)
                return -ENOMEM;

        ctx->dev = &pdev->dev;
        platform_set_drvdata(pdev, ctx);
        cl = &ctx->mbox_client;

        spin_lock_init(&ctx->kfifo_lock);
        mutex_init(&ctx->rd_mutex);

        rc = kfifo_alloc(&ctx->async_msg_fifo,
                         sizeof(struct slimpro_resp_msg) * ASYNC_MSG_FIFO_SIZE,
                         GFP_KERNEL);
        if (rc)
                return -ENOMEM;

        INIT_WORK(&ctx->workq, xgene_hwmon_evt_work);

        /* Request mailbox channel */
        cl->dev = &pdev->dev;
        cl->tx_done = xgene_hwmon_tx_done;
        cl->tx_block = false;
        cl->tx_tout = MBOX_OP_TIMEOUTMS;
        cl->knows_txdone = false;
        if (acpi_disabled) {
                cl->rx_callback = xgene_hwmon_rx_cb;
                ctx->mbox_chan = mbox_request_channel(cl, 0);
                if (IS_ERR(ctx->mbox_chan)) {
                        dev_err(&pdev->dev,
                                "SLIMpro mailbox channel request failed\n");
                        rc = -ENODEV;
                        goto out_mbox_free;
                }
        } else {
                struct acpi_pcct_hw_reduced *cppc_ss;
                const struct acpi_device_id *acpi_id;
                int version;

                acpi_id = acpi_match_device(pdev->dev.driver->acpi_match_table,
                                            &pdev->dev);
                if (!acpi_id)
                        return -EINVAL;

                version = (int)acpi_id->driver_data;

                if (device_property_read_u32(&pdev->dev, "pcc-channel",
                                             &ctx->mbox_idx)) {
                        dev_err(&pdev->dev, "no pcc-channel property\n");
                        rc = -ENODEV;
                        goto out_mbox_free;
                }

                cl->rx_callback = xgene_hwmon_pcc_rx_cb;
                ctx->mbox_chan = pcc_mbox_request_channel(cl, ctx->mbox_idx);
                if (IS_ERR(ctx->mbox_chan)) {
                        dev_err(&pdev->dev,
                                "PPC channel request failed\n");
                        rc = -ENODEV;
                        goto out_mbox_free;
                }

                /*
                 * 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 = ctx->mbox_chan->con_priv;
                if (!cppc_ss) {
                        dev_err(&pdev->dev, "PPC subspace not found\n");
                        rc = -ENODEV;
                        goto out;
                }

                if (!ctx->mbox_chan->mbox->txdone_irq) {
                        dev_err(&pdev->dev, "PCC IRQ not supported\n");
                        rc = -ENODEV;
                        goto out;
                }

                /*
                 * This is the shared communication region
                 * for the OS and Platform to communicate over.
                 */
                ctx->comm_base_addr = cppc_ss->base_address;
                if (ctx->comm_base_addr) {
                        if (version == XGENE_HWMON_V2)
                                ctx->pcc_comm_addr = (void __force *)ioremap(
                                                        ctx->comm_base_addr,
                                                        cppc_ss->length);
                        else
                                ctx->pcc_comm_addr = memremap(
                                                        ctx->comm_base_addr,
                                                        cppc_ss->length,
                                                        MEMREMAP_WB);
                } else {
                        dev_err(&pdev->dev, "Failed to get PCC comm region\n");
                        rc = -ENODEV;
                        goto out;
                }

                if (!ctx->pcc_comm_addr) {
                        dev_err(&pdev->dev,
                                "Failed to ioremap PCC comm region\n");
                        rc = -ENOMEM;
                        goto out;
                }

                /*
                 * 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.
                 */
                ctx->usecs_lat = PCC_NUM_RETRIES * cppc_ss->latency;
        }

        ctx->hwmon_dev = hwmon_device_register_with_groups(ctx->dev,
                                                           "apm_xgene",
                                                           ctx,
                                                           xgene_hwmon_groups);
        if (IS_ERR(ctx->hwmon_dev)) {
                dev_err(&pdev->dev, "Failed to register HW monitor device\n");
                rc = PTR_ERR(ctx->hwmon_dev);
                goto out;
        }

        /*
         * Schedule the bottom handler if there is a pending message.
         */
        schedule_work(&ctx->workq);

        dev_info(&pdev->dev, "APM X-Gene SoC HW monitor driver registered\n");

        return 0;

out:
        if (acpi_disabled)
                mbox_free_channel(ctx->mbox_chan);
        else
                pcc_mbox_free_channel(ctx->mbox_chan);
out_mbox_free:
        kfifo_free(&ctx->async_msg_fifo);

        return rc;
}

static int xgene_hwmon_remove(struct platform_device *pdev)
{
        struct xgene_hwmon_dev *ctx = platform_get_drvdata(pdev);

        hwmon_device_unregister(ctx->hwmon_dev);
        kfifo_free(&ctx->async_msg_fifo);
        if (acpi_disabled)
                mbox_free_channel(ctx->mbox_chan);
        else
                pcc_mbox_free_channel(ctx->mbox_chan);

        return 0;
}

static const struct of_device_id xgene_hwmon_of_match[] = {
        {.compatible = "apm,xgene-slimpro-hwmon"},
        {}
};
MODULE_DEVICE_TABLE(of, xgene_hwmon_of_match);

static struct platform_driver xgene_hwmon_driver __refdata = {
        .probe = xgene_hwmon_probe,
        .remove = xgene_hwmon_remove,
        .driver = {
                .name = "xgene-slimpro-hwmon",
                .of_match_table = xgene_hwmon_of_match,
                .acpi_match_table = ACPI_PTR(xgene_hwmon_acpi_match),
        },
};
module_platform_driver(xgene_hwmon_driver);

MODULE_DESCRIPTION("APM X-Gene SoC hardware monitor");
MODULE_LICENSE("GPL");