// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) IBM Corporation 2017
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERGCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/device.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/fsi.h>
#include <linux/fsi-sbefifo.h>
#include <linux/kernel.h>
#include <linux/cdev.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_platform.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/delay.h>
#include <linux/uio.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>

/*
 * The SBEFIFO is a pipe-like FSI device for communicating with
 * the self boot engine on POWER processors.
 */

#define DEVICE_NAME             "sbefifo"
#define FSI_ENGID_SBE           0x22

/*
 * Register layout
 */

/* Register banks */
#define SBEFIFO_UP              0x00            /* FSI -> Host */
#define SBEFIFO_DOWN            0x40            /* Host -> FSI */

/* Per-bank registers */
#define SBEFIFO_FIFO            0x00            /* The FIFO itself */
#define SBEFIFO_STS             0x04            /* Status register */
#define   SBEFIFO_STS_PARITY_ERR        0x20000000
#define   SBEFIFO_STS_RESET_REQ         0x02000000
#define   SBEFIFO_STS_GOT_EOT           0x00800000
#define   SBEFIFO_STS_MAX_XFER_LIMIT    0x00400000
#define   SBEFIFO_STS_FULL              0x00200000
#define   SBEFIFO_STS_EMPTY             0x00100000
#define   SBEFIFO_STS_ECNT_MASK         0x000f0000
#define   SBEFIFO_STS_ECNT_SHIFT        16
#define   SBEFIFO_STS_VALID_MASK        0x0000ff00
#define   SBEFIFO_STS_VALID_SHIFT       8
#define   SBEFIFO_STS_EOT_MASK          0x000000ff
#define   SBEFIFO_STS_EOT_SHIFT         0
#define SBEFIFO_EOT_RAISE       0x08            /* (Up only) Set End Of Transfer */
#define SBEFIFO_REQ_RESET       0x0C            /* (Up only) Reset Request */
#define SBEFIFO_PERFORM_RESET   0x10            /* (Down only) Perform Reset */
#define SBEFIFO_EOT_ACK         0x14            /* (Down only) Acknowledge EOT */
#define SBEFIFO_DOWN_MAX        0x18            /* (Down only) Max transfer */

/* CFAM GP Mailbox SelfBoot Message register */
#define CFAM_GP_MBOX_SBM_ADDR   0x2824  /* Converted 0x2809 */

#define CFAM_SBM_SBE_BOOTED             0x80000000
#define CFAM_SBM_SBE_ASYNC_FFDC         0x40000000
#define CFAM_SBM_SBE_STATE_MASK         0x00f00000
#define CFAM_SBM_SBE_STATE_SHIFT        20

enum sbe_state
{
        SBE_STATE_UNKNOWN = 0x0, // Unkown, initial state
        SBE_STATE_IPLING  = 0x1, // IPL'ing - autonomous mode (transient)
        SBE_STATE_ISTEP   = 0x2, // ISTEP - Running IPL by steps (transient)
        SBE_STATE_MPIPL   = 0x3, // MPIPL
        SBE_STATE_RUNTIME = 0x4, // SBE Runtime
        SBE_STATE_DMT     = 0x5, // Dead Man Timer State (transient)
        SBE_STATE_DUMP    = 0x6, // Dumping
        SBE_STATE_FAILURE = 0x7, // Internal SBE failure
        SBE_STATE_QUIESCE = 0x8, // Final state - needs SBE reset to get out
};

/* FIFO depth */
#define SBEFIFO_FIFO_DEPTH              8

/* Helpers */
#define sbefifo_empty(sts)      ((sts) & SBEFIFO_STS_EMPTY)
#define sbefifo_full(sts)       ((sts) & SBEFIFO_STS_FULL)
#define sbefifo_parity_err(sts) ((sts) & SBEFIFO_STS_PARITY_ERR)
#define sbefifo_populated(sts)  (((sts) & SBEFIFO_STS_ECNT_MASK) >> SBEFIFO_STS_ECNT_SHIFT)
#define sbefifo_vacant(sts)     (SBEFIFO_FIFO_DEPTH - sbefifo_populated(sts))
#define sbefifo_eot_set(sts)    (((sts) & SBEFIFO_STS_EOT_MASK) >> SBEFIFO_STS_EOT_SHIFT)

/* Reset request timeout in ms */
#define SBEFIFO_RESET_TIMEOUT           10000

/* Timeouts for commands in ms */
#define SBEFIFO_TIMEOUT_START_CMD       10000
#define SBEFIFO_TIMEOUT_IN_CMD          1000
#define SBEFIFO_TIMEOUT_START_RSP       10000
#define SBEFIFO_TIMEOUT_IN_RSP          1000

/* Other constants */
#define SBEFIFO_MAX_USER_CMD_LEN        (0x100000 + PAGE_SIZE)
#define SBEFIFO_RESET_MAGIC             0x52534554 /* "RSET" */

struct sbefifo {
        uint32_t                magic;
#define SBEFIFO_MAGIC           0x53424546 /* "SBEF" */
        struct fsi_device       *fsi_dev;
        struct device           dev;
        struct cdev             cdev;
        struct mutex            lock;
        bool                    broken;
        bool                    dead;
        bool                    async_ffdc;
};

struct sbefifo_user {
        struct sbefifo          *sbefifo;
        struct mutex            file_lock;
        void                    *cmd_page;
        void                    *pending_cmd;
        size_t                  pending_len;
};

static DEFINE_MUTEX(sbefifo_ffdc_mutex);


static void __sbefifo_dump_ffdc(struct device *dev, const __be32 *ffdc,
                                size_t ffdc_sz, bool internal)
{
        int pack = 0;
#define FFDC_LSIZE      60
        static char ffdc_line[FFDC_LSIZE];
        char *p = ffdc_line;

        while (ffdc_sz) {
                u32 w0, w1, w2, i;
                if (ffdc_sz < 3) {
                        dev_err(dev, "SBE invalid FFDC package size %zd\n", ffdc_sz);
                        return;
                }
                w0 = be32_to_cpu(*(ffdc++));
                w1 = be32_to_cpu(*(ffdc++));
                w2 = be32_to_cpu(*(ffdc++));
                ffdc_sz -= 3;
                if ((w0 >> 16) != 0xFFDC) {
                        dev_err(dev, "SBE invalid FFDC package signature %08x %08x %08x\n",
                                w0, w1, w2);
                        break;
                }
                w0 &= 0xffff;
                if (w0 > ffdc_sz) {
                        dev_err(dev, "SBE FFDC package len %d words but only %zd remaining\n",
                                w0, ffdc_sz);
                        w0 = ffdc_sz;
                        break;
                }
                if (internal) {
                        dev_warn(dev, "+---- SBE FFDC package %d for async err -----+\n",
                                 pack++);
                } else {
                        dev_warn(dev, "+---- SBE FFDC package %d for cmd %02x:%02x -----+\n",
                                 pack++, (w1 >> 8) & 0xff, w1 & 0xff);
                }
                dev_warn(dev, "| Response code: %08x                   |\n", w2);
                dev_warn(dev, "|-------------------------------------------|\n");
                for (i = 0; i < w0; i++) {
                        if ((i & 3) == 0) {
                                p = ffdc_line;
                                p += sprintf(p, "| %04x:", i << 4);
                        }
                        p += sprintf(p, " %08x", be32_to_cpu(*(ffdc++)));
                        ffdc_sz--;
                        if ((i & 3) == 3 || i == (w0 - 1)) {
                                while ((i & 3) < 3) {
                                        p += sprintf(p, "         ");
                                        i++;
                                }
                                dev_warn(dev, "%s |\n", ffdc_line);
                        }
                }
                dev_warn(dev, "+-------------------------------------------+\n");
        }
}

static void sbefifo_dump_ffdc(struct device *dev, const __be32 *ffdc,
                              size_t ffdc_sz, bool internal)
{
        mutex_lock(&sbefifo_ffdc_mutex);
        __sbefifo_dump_ffdc(dev, ffdc, ffdc_sz, internal);
        mutex_unlock(&sbefifo_ffdc_mutex);
}

int sbefifo_parse_status(struct device *dev, u16 cmd, __be32 *response,
                         size_t resp_len, size_t *data_len)
{
        u32 dh, s0, s1;
        size_t ffdc_sz;

        if (resp_len < 3) {
                pr_debug("sbefifo: cmd %04x, response too small: %zd\n",
                         cmd, resp_len);
                return -ENXIO;
        }
        dh = be32_to_cpu(response[resp_len - 1]);
        if (dh > resp_len || dh < 3) {
                dev_err(dev, "SBE cmd %02x:%02x status offset out of range: %d/%zd\n",
                        cmd >> 8, cmd & 0xff, dh, resp_len);
                return -ENXIO;
        }
        s0 = be32_to_cpu(response[resp_len - dh]);
        s1 = be32_to_cpu(response[resp_len - dh + 1]);
        if (((s0 >> 16) != 0xC0DE) || ((s0 & 0xffff) != cmd)) {
                dev_err(dev, "SBE cmd %02x:%02x, status signature invalid: 0x%08x 0x%08x\n",
                        cmd >> 8, cmd & 0xff, s0, s1);
                return -ENXIO;
        }
        if (s1 != 0) {
                ffdc_sz = dh - 3;
                dev_warn(dev, "SBE error cmd %02x:%02x status=%04x:%04x\n",
                         cmd >> 8, cmd & 0xff, s1 >> 16, s1 & 0xffff);
                if (ffdc_sz)
                        sbefifo_dump_ffdc(dev, &response[resp_len - dh + 2],
                                          ffdc_sz, false);
        }
        if (data_len)
                *data_len = resp_len - dh;

        /*
         * Primary status don't have the top bit set, so can't be confused with
         * Linux negative error codes, so return the status word whole.
         */
        return s1;
}
EXPORT_SYMBOL_GPL(sbefifo_parse_status);

static int sbefifo_regr(struct sbefifo *sbefifo, int reg, u32 *word)
{
        __be32 raw_word;
        int rc;

        rc = fsi_device_read(sbefifo->fsi_dev, reg, &raw_word,
                             sizeof(raw_word));
        if (rc)
                return rc;

        *word = be32_to_cpu(raw_word);

        return 0;
}

static int sbefifo_regw(struct sbefifo *sbefifo, int reg, u32 word)
{
        __be32 raw_word = cpu_to_be32(word);

        return fsi_device_write(sbefifo->fsi_dev, reg, &raw_word,
                                sizeof(raw_word));
}

static int sbefifo_check_sbe_state(struct sbefifo *sbefifo)
{
        __be32 raw_word;
        u32 sbm;
        int rc;

        rc = fsi_slave_read(sbefifo->fsi_dev->slave, CFAM_GP_MBOX_SBM_ADDR,
                            &raw_word, sizeof(raw_word));
        if (rc)
                return rc;
        sbm = be32_to_cpu(raw_word);

        /* SBE booted at all ? */
        if (!(sbm & CFAM_SBM_SBE_BOOTED))
                return -ESHUTDOWN;

        /* Check its state */
        switch ((sbm & CFAM_SBM_SBE_STATE_MASK) >> CFAM_SBM_SBE_STATE_SHIFT) {
        case SBE_STATE_UNKNOWN:
                return -ESHUTDOWN;
        case SBE_STATE_DMT:
                return -EBUSY;
        case SBE_STATE_IPLING:
        case SBE_STATE_ISTEP:
        case SBE_STATE_MPIPL:
        case SBE_STATE_RUNTIME:
        case SBE_STATE_DUMP: /* Not sure about that one */
                break;
        case SBE_STATE_FAILURE:
        case SBE_STATE_QUIESCE:
                return -ESHUTDOWN;
        }

        /* Is there async FFDC available ? Remember it */
        if (sbm & CFAM_SBM_SBE_ASYNC_FFDC)
                sbefifo->async_ffdc = true;

        return 0;
}

/* Don't flip endianness of data to/from FIFO, just pass through. */
static int sbefifo_down_read(struct sbefifo *sbefifo, __be32 *word)
{
        return fsi_device_read(sbefifo->fsi_dev, SBEFIFO_DOWN, word,
                               sizeof(*word));
}

static int sbefifo_up_write(struct sbefifo *sbefifo, __be32 word)
{
        return fsi_device_write(sbefifo->fsi_dev, SBEFIFO_UP, &word,
                                sizeof(word));
}

static int sbefifo_request_reset(struct sbefifo *sbefifo)
{
        struct device *dev = &sbefifo->fsi_dev->dev;
        u32 status, timeout;
        int rc;

        dev_dbg(dev, "Requesting FIFO reset\n");

        /* Mark broken first, will be cleared if reset succeeds */
        sbefifo->broken = true;

        /* Send reset request */
        rc = sbefifo_regw(sbefifo, SBEFIFO_UP | SBEFIFO_REQ_RESET, 1);
        if (rc) {
                dev_err(dev, "Sending reset request failed, rc=%d\n", rc);
                return rc;
        }

        /* Wait for it to complete */
        for (timeout = 0; timeout < SBEFIFO_RESET_TIMEOUT; timeout++) {
                rc = sbefifo_regr(sbefifo, SBEFIFO_UP | SBEFIFO_STS, &status);
                if (rc) {
                        dev_err(dev, "Failed to read UP fifo status during reset"
                                " , rc=%d\n", rc);
                        return rc;
                }

                if (!(status & SBEFIFO_STS_RESET_REQ)) {
                        dev_dbg(dev, "FIFO reset done\n");
                        sbefifo->broken = false;
                        return 0;
                }

                msleep(1);
        }
        dev_err(dev, "FIFO reset timed out\n");

        return -ETIMEDOUT;
}

static int sbefifo_cleanup_hw(struct sbefifo *sbefifo)
{
        struct device *dev = &sbefifo->fsi_dev->dev;
        u32 up_status, down_status;
        bool need_reset = false;
        int rc;

        rc = sbefifo_check_sbe_state(sbefifo);
        if (rc) {
                dev_dbg(dev, "SBE state=%d\n", rc);
                return rc;
        }

        /* If broken, we don't need to look at status, go straight to reset */
        if (sbefifo->broken)
                goto do_reset;

        rc = sbefifo_regr(sbefifo, SBEFIFO_UP | SBEFIFO_STS, &up_status);
        if (rc) {
                dev_err(dev, "Cleanup: Reading UP status failed, rc=%d\n", rc);

                /* Will try reset again on next attempt at using it */
                sbefifo->broken = true;
                return rc;
        }

        rc = sbefifo_regr(sbefifo, SBEFIFO_DOWN | SBEFIFO_STS, &down_status);
        if (rc) {
                dev_err(dev, "Cleanup: Reading DOWN status failed, rc=%d\n", rc);

                /* Will try reset again on next attempt at using it */
                sbefifo->broken = true;
                return rc;
        }

        /* The FIFO already contains a reset request from the SBE ? */
        if (down_status & SBEFIFO_STS_RESET_REQ) {
                dev_info(dev, "Cleanup: FIFO reset request set, resetting\n");
                rc = sbefifo_regw(sbefifo, SBEFIFO_UP, SBEFIFO_PERFORM_RESET);
                if (rc) {
                        sbefifo->broken = true;
                        dev_err(dev, "Cleanup: Reset reg write failed, rc=%d\n", rc);
                        return rc;
                }
                sbefifo->broken = false;
                return 0;
        }

        /* Parity error on either FIFO ? */
        if ((up_status | down_status) & SBEFIFO_STS_PARITY_ERR)
                need_reset = true;

        /* Either FIFO not empty ? */
        if (!((up_status & down_status) & SBEFIFO_STS_EMPTY))
                need_reset = true;

        if (!need_reset)
                return 0;

        dev_info(dev, "Cleanup: FIFO not clean (up=0x%08x down=0x%08x)\n",
                 up_status, down_status);

 do_reset:

        /* Mark broken, will be cleared if/when reset succeeds */
        return sbefifo_request_reset(sbefifo);
}

static int sbefifo_wait(struct sbefifo *sbefifo, bool up,
                        u32 *status, unsigned long timeout)
{
        struct device *dev = &sbefifo->fsi_dev->dev;
        unsigned long end_time;
        bool ready = false;
        u32 addr, sts = 0;
        int rc;

        dev_vdbg(dev, "Wait on %s fifo...\n", up ? "up" : "down");

        addr = (up ? SBEFIFO_UP : SBEFIFO_DOWN) | SBEFIFO_STS;

        end_time = jiffies + timeout;
        while (!time_after(jiffies, end_time)) {
                cond_resched();
                rc = sbefifo_regr(sbefifo, addr, &sts);
                if (rc < 0) {
                        dev_err(dev, "FSI error %d reading status register\n", rc);
                        return rc;
                }
                if (!up && sbefifo_parity_err(sts)) {
                        dev_err(dev, "Parity error in DOWN FIFO\n");
                        return -ENXIO;
                }
                ready = !(up ? sbefifo_full(sts) : sbefifo_empty(sts));
                if (ready)
                        break;
        }
        if (!ready) {
                dev_err(dev, "%s FIFO Timeout ! status=%08x\n", up ? "UP" : "DOWN", sts);
                return -ETIMEDOUT;
        }
        dev_vdbg(dev, "End of wait status: %08x\n", sts);

        *status = sts;

        return 0;
}

static int sbefifo_send_command(struct sbefifo *sbefifo,
                                const __be32 *command, size_t cmd_len)
{
        struct device *dev = &sbefifo->fsi_dev->dev;
        size_t len, chunk, vacant = 0, remaining = cmd_len;
        unsigned long timeout;
        u32 status;
        int rc;

        dev_vdbg(dev, "sending command (%zd words, cmd=%04x)\n",
                 cmd_len, be32_to_cpu(command[1]));

        /* As long as there's something to send */
        timeout = msecs_to_jiffies(SBEFIFO_TIMEOUT_START_CMD);
        while (remaining) {
                /* Wait for room in the FIFO */
                rc = sbefifo_wait(sbefifo, true, &status, timeout);
                if (rc < 0)
                        return rc;
                timeout = msecs_to_jiffies(SBEFIFO_TIMEOUT_IN_CMD);

                vacant = sbefifo_vacant(status);
                len = chunk = min(vacant, remaining);

                dev_vdbg(dev, "  status=%08x vacant=%zd chunk=%zd\n",
                         status, vacant, chunk);

                /* Write as much as we can */
                while (len--) {
                        rc = sbefifo_up_write(sbefifo, *(command++));
                        if (rc) {
                                dev_err(dev, "FSI error %d writing UP FIFO\n", rc);
                                return rc;
                        }
                }
                remaining -= chunk;
                vacant -= chunk;
        }

        /* If there's no room left, wait for some to write EOT */
        if (!vacant) {
                rc = sbefifo_wait(sbefifo, true, &status, timeout);
                if (rc)
                        return rc;
        }

        /* Send an EOT */
        rc = sbefifo_regw(sbefifo, SBEFIFO_UP | SBEFIFO_EOT_RAISE, 0);
        if (rc)
                dev_err(dev, "FSI error %d writing EOT\n", rc);
        return rc;
}

static int sbefifo_read_response(struct sbefifo *sbefifo, struct iov_iter *response)
{
        struct device *dev = &sbefifo->fsi_dev->dev;
        u32 status, eot_set;
        unsigned long timeout;
        bool overflow = false;
        __be32 data;
        size_t len;
        int rc;

        dev_vdbg(dev, "reading response, buflen = %zd\n", iov_iter_count(response));

        timeout = msecs_to_jiffies(SBEFIFO_TIMEOUT_START_RSP);
        for (;;) {
                /* Grab FIFO status (this will handle parity errors) */
                rc = sbefifo_wait(sbefifo, false, &status, timeout);
                if (rc < 0)
                        return rc;
                timeout = msecs_to_jiffies(SBEFIFO_TIMEOUT_IN_RSP);

                /* Decode status */
                len = sbefifo_populated(status);
                eot_set = sbefifo_eot_set(status);

                dev_vdbg(dev, "  chunk size %zd eot_set=0x%x\n", len, eot_set);

                /* Go through the chunk */
                while(len--) {
                        /* Read the data */
                        rc = sbefifo_down_read(sbefifo, &data);
                        if (rc < 0)
                                return rc;

                        /* Was it an EOT ? */
                        if (eot_set & 0x80) {
                                /*
                                 * There should be nothing else in the FIFO,
                                 * if there is, mark broken, this will force
                                 * a reset on next use, but don't fail the
                                 * command.
                                 */
                                if (len) {
                                        dev_warn(dev, "FIFO read hit"
                                                 " EOT with still %zd data\n",
                                                 len);
                                        sbefifo->broken = true;
                                }

                                /* We are done */
                                rc = sbefifo_regw(sbefifo,
                                                  SBEFIFO_DOWN | SBEFIFO_EOT_ACK, 0);

                                /*
                                 * If that write fail, still complete the request but mark
                                 * the fifo as broken for subsequent reset (not much else
                                 * we can do here).
                                 */
                                if (rc) {
                                        dev_err(dev, "FSI error %d ack'ing EOT\n", rc);
                                        sbefifo->broken = true;
                                }

                                /* Tell whether we overflowed */
                                return overflow ? -EOVERFLOW : 0;
                        }

                        /* Store it if there is room */
                        if (iov_iter_count(response) >= sizeof(__be32)) {
                                if (copy_to_iter(&data, sizeof(__be32), response) < sizeof(__be32))
                                        return -EFAULT;
                        } else {
                                dev_vdbg(dev, "Response overflowed !\n");

                                overflow = true;
                        }

                        /* Next EOT bit */
                        eot_set <<= 1;
                }
        }
        /* Shouldn't happen */
        return -EIO;
}

static int sbefifo_do_command(struct sbefifo *sbefifo,
                              const __be32 *command, size_t cmd_len,
                              struct iov_iter *response)
{
        /* Try sending the command */
        int rc = sbefifo_send_command(sbefifo, command, cmd_len);
        if (rc)
                return rc;

        /* Now, get the response */
        return sbefifo_read_response(sbefifo, response);
}

static void sbefifo_collect_async_ffdc(struct sbefifo *sbefifo)
{
        struct device *dev = &sbefifo->fsi_dev->dev;
        struct iov_iter ffdc_iter;
        struct kvec ffdc_iov;
        __be32 *ffdc;
        size_t ffdc_sz;
        __be32 cmd[2];
        int rc;

        sbefifo->async_ffdc = false;
        ffdc = vmalloc(SBEFIFO_MAX_FFDC_SIZE);
        if (!ffdc) {
                dev_err(dev, "Failed to allocate SBE FFDC buffer\n");
                return;
        }
        ffdc_iov.iov_base = ffdc;
        ffdc_iov.iov_len = SBEFIFO_MAX_FFDC_SIZE;
        iov_iter_kvec(&ffdc_iter, WRITE, &ffdc_iov, 1, SBEFIFO_MAX_FFDC_SIZE);
        cmd[0] = cpu_to_be32(2);
        cmd[1] = cpu_to_be32(SBEFIFO_CMD_GET_SBE_FFDC);
        rc = sbefifo_do_command(sbefifo, cmd, 2, &ffdc_iter);
        if (rc != 0) {
                dev_err(dev, "Error %d retrieving SBE FFDC\n", rc);
                goto bail;
        }
        ffdc_sz = SBEFIFO_MAX_FFDC_SIZE - iov_iter_count(&ffdc_iter);
        ffdc_sz /= sizeof(__be32);
        rc = sbefifo_parse_status(dev, SBEFIFO_CMD_GET_SBE_FFDC, ffdc,
                                  ffdc_sz, &ffdc_sz);
        if (rc != 0) {
                dev_err(dev, "Error %d decoding SBE FFDC\n", rc);
                goto bail;
        }
        if (ffdc_sz > 0)
                sbefifo_dump_ffdc(dev, ffdc, ffdc_sz, true);
 bail:
        vfree(ffdc);

}

static int __sbefifo_submit(struct sbefifo *sbefifo,
                            const __be32 *command, size_t cmd_len,
                            struct iov_iter *response)
{
        struct device *dev = &sbefifo->fsi_dev->dev;
        int rc;

        if (sbefifo->dead)
                return -ENODEV;

        if (cmd_len < 2 || be32_to_cpu(command[0]) != cmd_len) {
                dev_vdbg(dev, "Invalid command len %zd (header: %d)\n",
                         cmd_len, be32_to_cpu(command[0]));
                return -EINVAL;
        }

        /* First ensure the HW is in a clean state */
        rc = sbefifo_cleanup_hw(sbefifo);
        if (rc)
                return rc;

        /* Look for async FFDC first if any */
        if (sbefifo->async_ffdc)
                sbefifo_collect_async_ffdc(sbefifo);

        rc = sbefifo_do_command(sbefifo, command, cmd_len, response);
        if (rc != 0 && rc != -EOVERFLOW)
                goto fail;
        return rc;
 fail:
        /*
         * On failure, attempt a reset. Ignore the result, it will mark
         * the fifo broken if the reset fails
         */
        sbefifo_request_reset(sbefifo);

        /* Return original error */
        return rc;
}

/**
 * sbefifo_submit() - Submit and SBE fifo command and receive response
 * @dev: The sbefifo device
 * @command: The raw command data
 * @cmd_len: The command size (in 32-bit words)
 * @response: The output response buffer
 * @resp_len: In: Response buffer size, Out: Response size
 *
 * This will perform the entire operation. If the reponse buffer
 * overflows, returns -EOVERFLOW
 */
int sbefifo_submit(struct device *dev, const __be32 *command, size_t cmd_len,
                   __be32 *response, size_t *resp_len)
{
        struct sbefifo *sbefifo;
        struct iov_iter resp_iter;
        struct kvec resp_iov;
        size_t rbytes;
        int rc;

        if (!dev)
                return -ENODEV;
        sbefifo = dev_get_drvdata(dev);
        if (!sbefifo)
                return -ENODEV;
        if (WARN_ON_ONCE(sbefifo->magic != SBEFIFO_MAGIC))
                return -ENODEV;
        if (!resp_len || !command || !response)
                return -EINVAL;

        /* Prepare iov iterator */
        rbytes = (*resp_len) * sizeof(__be32);
        resp_iov.iov_base = response;
        resp_iov.iov_len = rbytes;
        iov_iter_kvec(&resp_iter, WRITE, &resp_iov, 1, rbytes);

        /* Perform the command */
        mutex_lock(&sbefifo->lock);
        rc = __sbefifo_submit(sbefifo, command, cmd_len, &resp_iter);
        mutex_unlock(&sbefifo->lock);

        /* Extract the response length */
        rbytes -= iov_iter_count(&resp_iter);
        *resp_len = rbytes / sizeof(__be32);

        return rc;
}
EXPORT_SYMBOL_GPL(sbefifo_submit);

/*
 * Char device interface
 */

static void sbefifo_release_command(struct sbefifo_user *user)
{
        if (is_vmalloc_addr(user->pending_cmd))
                vfree(user->pending_cmd);
        user->pending_cmd = NULL;
        user->pending_len = 0;
}

static int sbefifo_user_open(struct inode *inode, struct file *file)
{
        struct sbefifo *sbefifo = container_of(inode->i_cdev, struct sbefifo, cdev);
        struct sbefifo_user *user;

        user = kzalloc(sizeof(struct sbefifo_user), GFP_KERNEL);
        if (!user)
                return -ENOMEM;

        file->private_data = user;
        user->sbefifo = sbefifo;
        user->cmd_page = (void *)__get_free_page(GFP_KERNEL);
        if (!user->cmd_page) {
                kfree(user);
                return -ENOMEM;
        }
        mutex_init(&user->file_lock);

        return 0;
}

static ssize_t sbefifo_user_read(struct file *file, char __user *buf,
                                 size_t len, loff_t *offset)
{
        struct sbefifo_user *user = file->private_data;
        struct sbefifo *sbefifo;
        struct iov_iter resp_iter;
        struct iovec resp_iov;
        size_t cmd_len;
        int rc;

        if (!user)
                return -EINVAL;
        sbefifo = user->sbefifo;
        if (len & 3)
                return -EINVAL;

        mutex_lock(&user->file_lock);

        /* Cronus relies on -EAGAIN after a short read */
        if (user->pending_len == 0) {
                rc = -EAGAIN;
                goto bail;
        }
        if (user->pending_len < 8) {
                rc = -EINVAL;
                goto bail;
        }
        cmd_len = user->pending_len >> 2;

        /* Prepare iov iterator */
        resp_iov.iov_base = buf;
        resp_iov.iov_len = len;
        iov_iter_init(&resp_iter, WRITE, &resp_iov, 1, len);

        /* Perform the command */
        mutex_lock(&sbefifo->lock);
        rc = __sbefifo_submit(sbefifo, user->pending_cmd, cmd_len, &resp_iter);
        mutex_unlock(&sbefifo->lock);
        if (rc < 0)
                goto bail;

        /* Extract the response length */
        rc = len - iov_iter_count(&resp_iter);
 bail:
        sbefifo_release_command(user);
        mutex_unlock(&user->file_lock);
        return rc;
}

static ssize_t sbefifo_user_write(struct file *file, const char __user *buf,
                                  size_t len, loff_t *offset)
{
        struct sbefifo_user *user = file->private_data;
        struct sbefifo *sbefifo;
        int rc = len;

        if (!user)
                return -EINVAL;
        sbefifo = user->sbefifo;
        if (len > SBEFIFO_MAX_USER_CMD_LEN)
                return -EINVAL;
        if (len & 3)
                return -EINVAL;

        mutex_lock(&user->file_lock);

        /* Can we use the pre-allocate buffer ? If not, allocate */
        if (len <= PAGE_SIZE)
                user->pending_cmd = user->cmd_page;
        else
                user->pending_cmd = vmalloc(len);
        if (!user->pending_cmd) {
                rc = -ENOMEM;
                goto bail;
        }

        /* Copy the command into the staging buffer */
        if (copy_from_user(user->pending_cmd, buf, len)) {
                rc = -EFAULT;
                goto bail;
        }

        /* Check for the magic reset command */
        if (len == 4 && be32_to_cpu(*(__be32 *)user->pending_cmd) ==
            SBEFIFO_RESET_MAGIC)  {

                /* Clear out any pending command */
                user->pending_len = 0;

                /* Trigger reset request */
                mutex_lock(&sbefifo->lock);
                rc = sbefifo_request_reset(user->sbefifo);
                mutex_unlock(&sbefifo->lock);
                if (rc == 0)
                        rc = 4;
                goto bail;
        }

        /* Update the staging buffer size */
        user->pending_len = len;
 bail:
        if (!user->pending_len)
                sbefifo_release_command(user);

        mutex_unlock(&user->file_lock);

        /* And that's it, we'll issue the command on a read */
        return rc;
}

static int sbefifo_user_release(struct inode *inode, struct file *file)
{
        struct sbefifo_user *user = file->private_data;

        if (!user)
                return -EINVAL;

        sbefifo_release_command(user);
        free_page((unsigned long)user->cmd_page);
        kfree(user);

        return 0;
}

static const struct file_operations sbefifo_fops = {
        .owner          = THIS_MODULE,
        .open           = sbefifo_user_open,
        .read           = sbefifo_user_read,
        .write          = sbefifo_user_write,
        .release        = sbefifo_user_release,
};

static void sbefifo_free(struct device *dev)
{
        struct sbefifo *sbefifo = container_of(dev, struct sbefifo, dev);

        put_device(&sbefifo->fsi_dev->dev);
        kfree(sbefifo);
}

/*
 * Probe/remove
 */

static int sbefifo_probe(struct device *dev)
{
        struct fsi_device *fsi_dev = to_fsi_dev(dev);
        struct sbefifo *sbefifo;
        struct device_node *np;
        struct platform_device *child;
        char child_name[32];
        int rc, didx, child_idx = 0;

        dev_dbg(dev, "Found sbefifo device\n");

        sbefifo = kzalloc(sizeof(*sbefifo), GFP_KERNEL);
        if (!sbefifo)
                return -ENOMEM;

        /* Grab a reference to the device (parent of our cdev), we'll drop it later */
        if (!get_device(dev)) {
                kfree(sbefifo);
                return -ENODEV;
        }

        sbefifo->magic = SBEFIFO_MAGIC;
        sbefifo->fsi_dev = fsi_dev;
        dev_set_drvdata(dev, sbefifo);
        mutex_init(&sbefifo->lock);

        /*
         * Try cleaning up the FIFO. If this fails, we still register the
         * driver and will try cleaning things up again on the next access.
         */
        rc = sbefifo_cleanup_hw(sbefifo);
        if (rc && rc != -ESHUTDOWN)
                dev_err(dev, "Initial HW cleanup failed, will retry later\n");

        /* Create chardev for userspace access */
        sbefifo->dev.type = &fsi_cdev_type;
        sbefifo->dev.parent = dev;
        sbefifo->dev.release = sbefifo_free;
        device_initialize(&sbefifo->dev);

        /* Allocate a minor in the FSI space */
        rc = fsi_get_new_minor(fsi_dev, fsi_dev_sbefifo, &sbefifo->dev.devt, &didx);
        if (rc)
                goto err;

        dev_set_name(&sbefifo->dev, "sbefifo%d", didx);
        cdev_init(&sbefifo->cdev, &sbefifo_fops);
        rc = cdev_device_add(&sbefifo->cdev, &sbefifo->dev);
        if (rc) {
                dev_err(dev, "Error %d creating char device %s\n",
                        rc, dev_name(&sbefifo->dev));
                goto err_free_minor;
        }

        /* Create platform devs for dts child nodes (occ, etc) */
        for_each_available_child_of_node(dev->of_node, np) {
                snprintf(child_name, sizeof(child_name), "%s-dev%d",
                         dev_name(&sbefifo->dev), child_idx++);
                child = of_platform_device_create(np, child_name, dev);
                if (!child)
                        dev_warn(dev, "failed to create child %s dev\n",
                                 child_name);
        }

        return 0;
 err_free_minor:
        fsi_free_minor(sbefifo->dev.devt);
 err:
        put_device(&sbefifo->dev);
        return rc;
}

static int sbefifo_unregister_child(struct device *dev, void *data)
{
        struct platform_device *child = to_platform_device(dev);

        of_device_unregister(child);
        if (dev->of_node)
                of_node_clear_flag(dev->of_node, OF_POPULATED);

        return 0;
}

static int sbefifo_remove(struct device *dev)
{
        struct sbefifo *sbefifo = dev_get_drvdata(dev);

        dev_dbg(dev, "Removing sbefifo device...\n");

        mutex_lock(&sbefifo->lock);
        sbefifo->dead = true;
        mutex_unlock(&sbefifo->lock);

        cdev_device_del(&sbefifo->cdev, &sbefifo->dev);
        fsi_free_minor(sbefifo->dev.devt);
        device_for_each_child(dev, NULL, sbefifo_unregister_child);
        put_device(&sbefifo->dev);

        return 0;
}

static const struct fsi_device_id sbefifo_ids[] = {
        {
                .engine_type = FSI_ENGID_SBE,
                .version = FSI_VERSION_ANY,
        },
        { 0 }
};

static struct fsi_driver sbefifo_drv = {
        .id_table = sbefifo_ids,
        .drv = {
                .name = DEVICE_NAME,
                .bus = &fsi_bus_type,
                .probe = sbefifo_probe,
                .remove = sbefifo_remove,
        }
};

static int sbefifo_init(void)
{
        return fsi_driver_register(&sbefifo_drv);
}

static void sbefifo_exit(void)
{
        fsi_driver_unregister(&sbefifo_drv);
}

module_init(sbefifo_init);
module_exit(sbefifo_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Brad Bishop <bradleyb@fuzziesquirrel.com>");
MODULE_AUTHOR("Eddie James <eajames@linux.vnet.ibm.com>");
MODULE_AUTHOR("Andrew Jeffery <andrew@aj.id.au>");
MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");
MODULE_DESCRIPTION("Linux device interface to the POWER Self Boot Engine");