treewide: remove redundant IS_ERR() before error code check

[linux/fpc-iii.git] / drivers / mfd / rave-sp.c

// SPDX-License-Identifier: GPL-2.0+

/*
 * Multifunction core driver for Zodiac Inflight Innovations RAVE
 * Supervisory Processor(SP) MCU that is connected via dedicated UART
 * port
 *
 * Copyright (C) 2017 Zodiac Inflight Innovations
 */

#include <linux/atomic.h>
#include <linux/crc-ccitt.h>
#include <linux/delay.h>
#include <linux/export.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/mfd/rave-sp.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/sched.h>
#include <linux/serdev.h>
#include <asm/unaligned.h>

/*
 * UART protocol using following entities:
 *  - message to MCU => ACK response
 *  - event from MCU => event ACK
 *
 * Frame structure:
 * <STX> <DATA> <CHECKSUM> <ETX>
 * Where:
 * - STX - is start of transmission character
 * - ETX - end of transmission
 * - DATA - payload
 * - CHECKSUM - checksum calculated on <DATA>
 *
 * If <DATA> or <CHECKSUM> contain one of control characters, then it is
 * escaped using <DLE> control code. Added <DLE> does not participate in
 * checksum calculation.
 */
#define RAVE_SP_STX                     0x02
#define RAVE_SP_ETX                     0x03
#define RAVE_SP_DLE                     0x10

#define RAVE_SP_MAX_DATA_SIZE           64
#define RAVE_SP_CHECKSUM_8B2C           1
#define RAVE_SP_CHECKSUM_CCITT          2
#define RAVE_SP_CHECKSUM_SIZE           RAVE_SP_CHECKSUM_CCITT
/*
 * We don't store STX, ETX and unescaped bytes, so Rx is only
 * DATA + CSUM
 */
#define RAVE_SP_RX_BUFFER_SIZE                          \
        (RAVE_SP_MAX_DATA_SIZE + RAVE_SP_CHECKSUM_SIZE)

#define RAVE_SP_STX_ETX_SIZE            2
/*
 * For Tx we have to have space for everything, STX, EXT and
 * potentially stuffed DATA + CSUM data + csum
 */
#define RAVE_SP_TX_BUFFER_SIZE                          \
        (RAVE_SP_STX_ETX_SIZE + 2 * RAVE_SP_RX_BUFFER_SIZE)

/**
 * enum rave_sp_deframer_state - Possible state for de-framer
 *
 * @RAVE_SP_EXPECT_SOF:          Scanning input for start-of-frame marker
 * @RAVE_SP_EXPECT_DATA:         Got start of frame marker, collecting frame
 * @RAVE_SP_EXPECT_ESCAPED_DATA: Got escape character, collecting escaped byte
 */
enum rave_sp_deframer_state {
        RAVE_SP_EXPECT_SOF,
        RAVE_SP_EXPECT_DATA,
        RAVE_SP_EXPECT_ESCAPED_DATA,
};

/**
 * struct rave_sp_deframer - Device protocol deframer
 *
 * @state:  Current state of the deframer
 * @data:   Buffer used to collect deframed data
 * @length: Number of bytes de-framed so far
 */
struct rave_sp_deframer {
        enum rave_sp_deframer_state state;
        unsigned char data[RAVE_SP_RX_BUFFER_SIZE];
        size_t length;
};

/**
 * struct rave_sp_reply - Reply as per RAVE device protocol
 *
 * @length:     Expected reply length
 * @data:       Buffer to store reply payload in
 * @code:       Expected reply code
 * @ackid:      Expected reply ACK ID
 * @completion: Successful reply reception completion
 */
struct rave_sp_reply {
        size_t length;
        void  *data;
        u8     code;
        u8     ackid;
        struct completion received;
};

/**
 * struct rave_sp_checksum - Variant specific checksum implementation details
 *
 * @length:     Calculated checksum length
 * @subroutine: Utilized checksum algorithm implementation
 */
struct rave_sp_checksum {
        size_t length;
        void (*subroutine)(const u8 *, size_t, u8 *);
};

struct rave_sp_version {
        u8     hardware;
        __le16 major;
        u8     minor;
        u8     letter[2];
} __packed;

struct rave_sp_status {
        struct rave_sp_version bootloader_version;
        struct rave_sp_version firmware_version;
        u16 rdu_eeprom_flag;
        u16 dds_eeprom_flag;
        u8  pic_flag;
        u8  orientation;
        u32 etc;
        s16 temp[2];
        u8  backlight_current[3];
        u8  dip_switch;
        u8  host_interrupt;
        u16 voltage_28;
        u8  i2c_device_status;
        u8  power_status;
        u8  general_status;
        u8  deprecated1;
        u8  power_led_status;
        u8  deprecated2;
        u8  periph_power_shutoff;
} __packed;

/**
 * struct rave_sp_variant_cmds - Variant specific command routines
 *
 * @translate:  Generic to variant specific command mapping routine
 * @get_status: Variant specific implementation of CMD_GET_STATUS
 */
struct rave_sp_variant_cmds {
        int (*translate)(enum rave_sp_command);
        int (*get_status)(struct rave_sp *sp, struct rave_sp_status *);
};

/**
 * struct rave_sp_variant - RAVE supervisory processor core variant
 *
 * @checksum:   Variant specific checksum implementation
 * @cmd:        Variant specific command pointer table
 *
 */
struct rave_sp_variant {
        const struct rave_sp_checksum *checksum;
        struct rave_sp_variant_cmds cmd;
};

/**
 * struct rave_sp - RAVE supervisory processor core
 *
 * @serdev:                     Pointer to underlying serdev
 * @deframer:                   Stored state of the protocol deframer
 * @ackid:                      ACK ID used in last reply sent to the device
 * @bus_lock:                   Lock to serialize access to the device
 * @reply_lock:                 Lock protecting @reply
 * @reply:                      Pointer to memory to store reply payload
 *
 * @variant:                    Device variant specific information
 * @event_notifier_list:        Input event notification chain
 *
 * @part_number_firmware:       Firmware version
 * @part_number_bootloader:     Bootloader version
 */
struct rave_sp {
        struct serdev_device *serdev;
        struct rave_sp_deframer deframer;
        atomic_t ackid;
        struct mutex bus_lock;
        struct mutex reply_lock;
        struct rave_sp_reply *reply;

        const struct rave_sp_variant *variant;
        struct blocking_notifier_head event_notifier_list;

        const char *part_number_firmware;
        const char *part_number_bootloader;
};

static bool rave_sp_id_is_event(u8 code)
{
        return (code & 0xF0) == RAVE_SP_EVNT_BASE;
}

static void rave_sp_unregister_event_notifier(struct device *dev, void *res)
{
        struct rave_sp *sp = dev_get_drvdata(dev->parent);
        struct notifier_block *nb = *(struct notifier_block **)res;
        struct blocking_notifier_head *bnh = &sp->event_notifier_list;

        WARN_ON(blocking_notifier_chain_unregister(bnh, nb));
}

int devm_rave_sp_register_event_notifier(struct device *dev,
                                         struct notifier_block *nb)
{
        struct rave_sp *sp = dev_get_drvdata(dev->parent);
        struct notifier_block **rcnb;
        int ret;

        rcnb = devres_alloc(rave_sp_unregister_event_notifier,
                            sizeof(*rcnb), GFP_KERNEL);
        if (!rcnb)
                return -ENOMEM;

        ret = blocking_notifier_chain_register(&sp->event_notifier_list, nb);
        if (!ret) {
                *rcnb = nb;
                devres_add(dev, rcnb);
        } else {
                devres_free(rcnb);
        }

        return ret;
}
EXPORT_SYMBOL_GPL(devm_rave_sp_register_event_notifier);

static void csum_8b2c(const u8 *buf, size_t size, u8 *crc)
{
        *crc = *buf++;
        size--;

        while (size--)
                *crc += *buf++;

        *crc = 1 + ~(*crc);
}

static void csum_ccitt(const u8 *buf, size_t size, u8 *crc)
{
        const u16 calculated = crc_ccitt_false(0xffff, buf, size);

        /*
         * While the rest of the wire protocol is little-endian,
         * CCITT-16 CRC in RDU2 device is sent out in big-endian order.
         */
        put_unaligned_be16(calculated, crc);
}

static void *stuff(unsigned char *dest, const unsigned char *src, size_t n)
{
        while (n--) {
                const unsigned char byte = *src++;

                switch (byte) {
                case RAVE_SP_STX:
                case RAVE_SP_ETX:
                case RAVE_SP_DLE:
                        *dest++ = RAVE_SP_DLE;
                        /* FALLTHROUGH */
                default:
                        *dest++ = byte;
                }
        }

        return dest;
}

static int rave_sp_write(struct rave_sp *sp, const u8 *data, u8 data_size)
{
        const size_t checksum_length = sp->variant->checksum->length;
        unsigned char frame[RAVE_SP_TX_BUFFER_SIZE];
        unsigned char crc[RAVE_SP_CHECKSUM_SIZE];
        unsigned char *dest = frame;
        size_t length;

        if (WARN_ON(checksum_length > sizeof(crc)))
                return -ENOMEM;

        if (WARN_ON(data_size > sizeof(frame)))
                return -ENOMEM;

        sp->variant->checksum->subroutine(data, data_size, crc);

        *dest++ = RAVE_SP_STX;
        dest = stuff(dest, data, data_size);
        dest = stuff(dest, crc, checksum_length);
        *dest++ = RAVE_SP_ETX;

        length = dest - frame;

        print_hex_dump_debug("rave-sp tx: ", DUMP_PREFIX_NONE,
                             16, 1, frame, length, false);

        return serdev_device_write(sp->serdev, frame, length, HZ);
}

static u8 rave_sp_reply_code(u8 command)
{
        /*
         * There isn't a single rule that describes command code ->
         * ACK code transformation, but, going through various
         * versions of ICDs, there appear to be three distinct groups
         * that can be described by simple transformation.
         */
        switch (command) {
        case 0xA0 ... 0xBE:
                /*
                 * Commands implemented by firmware found in RDU1 and
                 * older devices all seem to obey the following rule
                 */
                return command + 0x20;
        case 0xE0 ... 0xEF:
                /*
                 * Events emitted by all versions of the firmare use
                 * least significant bit to get an ACK code
                 */
                return command | 0x01;
        default:
                /*
                 * Commands implemented by firmware found in RDU2 are
                 * similar to "old" commands, but they use slightly
                 * different offset
                 */
                return command + 0x40;
        }
}

int rave_sp_exec(struct rave_sp *sp,
                 void *__data,  size_t data_size,
                 void *reply_data, size_t reply_data_size)
{
        struct rave_sp_reply reply = {
                .data     = reply_data,
                .length   = reply_data_size,
                .received = COMPLETION_INITIALIZER_ONSTACK(reply.received),
        };
        unsigned char *data = __data;
        int command, ret = 0;
        u8 ackid;

        command = sp->variant->cmd.translate(data[0]);
        if (command < 0)
                return command;

        ackid       = atomic_inc_return(&sp->ackid);
        reply.ackid = ackid;
        reply.code  = rave_sp_reply_code((u8)command),

        mutex_lock(&sp->bus_lock);

        mutex_lock(&sp->reply_lock);
        sp->reply = &reply;
        mutex_unlock(&sp->reply_lock);

        data[0] = command;
        data[1] = ackid;

        rave_sp_write(sp, data, data_size);

        if (!wait_for_completion_timeout(&reply.received, HZ)) {
                dev_err(&sp->serdev->dev, "Command timeout\n");
                ret = -ETIMEDOUT;

                mutex_lock(&sp->reply_lock);
                sp->reply = NULL;
                mutex_unlock(&sp->reply_lock);
        }

        mutex_unlock(&sp->bus_lock);
        return ret;
}
EXPORT_SYMBOL_GPL(rave_sp_exec);

static void rave_sp_receive_event(struct rave_sp *sp,
                                  const unsigned char *data, size_t length)
{
        u8 cmd[] = {
                [0] = rave_sp_reply_code(data[0]),
                [1] = data[1],
        };

        rave_sp_write(sp, cmd, sizeof(cmd));

        blocking_notifier_call_chain(&sp->event_notifier_list,
                                     rave_sp_action_pack(data[0], data[2]),
                                     NULL);
}

static void rave_sp_receive_reply(struct rave_sp *sp,
                                  const unsigned char *data, size_t length)
{
        struct device *dev = &sp->serdev->dev;
        struct rave_sp_reply *reply;
        const  size_t payload_length = length - 2;

        mutex_lock(&sp->reply_lock);
        reply = sp->reply;

        if (reply) {
                if (reply->code == data[0] && reply->ackid == data[1] &&
                    payload_length >= reply->length) {
                        /*
                         * We are relying on memcpy(dst, src, 0) to be a no-op
                         * when handling commands that have a no-payload reply
                         */
                        memcpy(reply->data, &data[2], reply->length);
                        complete(&reply->received);
                        sp->reply = NULL;
                } else {
                        dev_err(dev, "Ignoring incorrect reply\n");
                        dev_dbg(dev, "Code:   expected = 0x%08x received = 0x%08x\n",
                                reply->code, data[0]);
                        dev_dbg(dev, "ACK ID: expected = 0x%08x received = 0x%08x\n",
                                reply->ackid, data[1]);
                        dev_dbg(dev, "Length: expected = %zu received = %zu\n",
                                reply->length, payload_length);
                }
        }

        mutex_unlock(&sp->reply_lock);
}

static void rave_sp_receive_frame(struct rave_sp *sp,
                                  const unsigned char *data,
                                  size_t length)
{
        const size_t checksum_length = sp->variant->checksum->length;
        const size_t payload_length  = length - checksum_length;
        const u8 *crc_reported       = &data[payload_length];
        struct device *dev           = &sp->serdev->dev;
        u8 crc_calculated[RAVE_SP_CHECKSUM_SIZE];

        if (unlikely(checksum_length > sizeof(crc_calculated))) {
                dev_warn(dev, "Checksum too long, dropping\n");
                return;
        }

        print_hex_dump_debug("rave-sp rx: ", DUMP_PREFIX_NONE,
                             16, 1, data, length, false);

        if (unlikely(length <= checksum_length)) {
                dev_warn(dev, "Dropping short frame\n");
                return;
        }

        sp->variant->checksum->subroutine(data, payload_length,
                                          crc_calculated);

        if (memcmp(crc_calculated, crc_reported, checksum_length)) {
                dev_warn(dev, "Dropping bad frame\n");
                return;
        }

        if (rave_sp_id_is_event(data[0]))
                rave_sp_receive_event(sp, data, length);
        else
                rave_sp_receive_reply(sp, data, length);
}

static int rave_sp_receive_buf(struct serdev_device *serdev,
                               const unsigned char *buf, size_t size)
{
        struct device *dev = &serdev->dev;
        struct rave_sp *sp = dev_get_drvdata(dev);
        struct rave_sp_deframer *deframer = &sp->deframer;
        const unsigned char *src = buf;
        const unsigned char *end = buf + size;

        while (src < end) {
                const unsigned char byte = *src++;

                switch (deframer->state) {
                case RAVE_SP_EXPECT_SOF:
                        if (byte == RAVE_SP_STX)
                                deframer->state = RAVE_SP_EXPECT_DATA;
                        break;

                case RAVE_SP_EXPECT_DATA:
                        /*
                         * Treat special byte values first
                         */
                        switch (byte) {
                        case RAVE_SP_ETX:
                                rave_sp_receive_frame(sp,
                                                      deframer->data,
                                                      deframer->length);
                                /*
                                 * Once we extracted a complete frame
                                 * out of a stream, we call it done
                                 * and proceed to bailing out while
                                 * resetting the framer to initial
                                 * state, regardless if we've consumed
                                 * all of the stream or not.
                                 */
                                goto reset_framer;
                        case RAVE_SP_STX:
                                dev_warn(dev, "Bad frame: STX before ETX\n");
                                /*
                                 * If we encounter second "start of
                                 * the frame" marker before seeing
                                 * corresponding "end of frame", we
                                 * reset the framer and ignore both:
                                 * frame started by first SOF and
                                 * frame started by current SOF.
                                 *
                                 * NOTE: The above means that only the
                                 * frame started by third SOF, sent
                                 * after this one will have a chance
                                 * to get throught.
                                 */
                                goto reset_framer;
                        case RAVE_SP_DLE:
                                deframer->state = RAVE_SP_EXPECT_ESCAPED_DATA;
                                /*
                                 * If we encounter escape sequence we
                                 * need to skip it and collect the
                                 * byte that follows. We do it by
                                 * forcing the next iteration of the
                                 * encompassing while loop.
                                 */
                                continue;
                        }
                        /*
                         * For the rest of the bytes, that are not
                         * speical snoflakes, we do the same thing
                         * that we do to escaped data - collect it in
                         * deframer buffer
                         */

                        /* FALLTHROUGH */

                case RAVE_SP_EXPECT_ESCAPED_DATA:
                        if (deframer->length == sizeof(deframer->data)) {
                                dev_warn(dev, "Bad frame: Too long\n");
                                /*
                                 * If the amount of data we've
                                 * accumulated for current frame so
                                 * far starts to exceed the capacity
                                 * of deframer's buffer, there's
                                 * nothing else we can do but to
                                 * discard that data and start
                                 * assemblying a new frame again
                                 */
                                goto reset_framer;
                        }

                        deframer->data[deframer->length++] = byte;

                        /*
                         * We've extracted out special byte, now we
                         * can go back to regular data collecting
                         */
                        deframer->state = RAVE_SP_EXPECT_DATA;
                        break;
                }
        }

        /*
         * The only way to get out of the above loop and end up here
         * is throught consuming all of the supplied data, so here we
         * report that we processed it all.
         */
        return size;

reset_framer:
        /*
         * NOTE: A number of codepaths that will drop us here will do
         * so before consuming all 'size' bytes of the data passed by
         * serdev layer. We rely on the fact that serdev layer will
         * re-execute this handler with the remainder of the Rx bytes
         * once we report actual number of bytes that we processed.
         */
        deframer->state  = RAVE_SP_EXPECT_SOF;
        deframer->length = 0;

        return src - buf;
}

static int rave_sp_rdu1_cmd_translate(enum rave_sp_command command)
{
        if (command >= RAVE_SP_CMD_STATUS &&
            command <= RAVE_SP_CMD_CONTROL_EVENTS)
                return command;

        return -EINVAL;
}

static int rave_sp_rdu2_cmd_translate(enum rave_sp_command command)
{
        if (command >= RAVE_SP_CMD_GET_FIRMWARE_VERSION &&
            command <= RAVE_SP_CMD_GET_GPIO_STATE)
                return command;

        if (command == RAVE_SP_CMD_REQ_COPPER_REV) {
                /*
                 * As per RDU2 ICD 3.4.47 CMD_GET_COPPER_REV code is
                 * different from that for RDU1 and it is set to 0x28.
                 */
                return 0x28;
        }

        return rave_sp_rdu1_cmd_translate(command);
}

static int rave_sp_default_cmd_translate(enum rave_sp_command command)
{
        /*
         * All of the following command codes were taken from "Table :
         * Communications Protocol Message Types" in section 3.3
         * "MESSAGE TYPES" of Rave PIC24 ICD.
         */
        switch (command) {
        case RAVE_SP_CMD_GET_FIRMWARE_VERSION:
                return 0x11;
        case RAVE_SP_CMD_GET_BOOTLOADER_VERSION:
                return 0x12;
        case RAVE_SP_CMD_BOOT_SOURCE:
                return 0x14;
        case RAVE_SP_CMD_SW_WDT:
                return 0x1C;
        case RAVE_SP_CMD_PET_WDT:
                return 0x1D;
        case RAVE_SP_CMD_RESET:
                return 0x1E;
        case RAVE_SP_CMD_RESET_REASON:
                return 0x1F;
        case RAVE_SP_CMD_RMB_EEPROM:
                return 0x20;
        default:
                return -EINVAL;
        }
}

static const char *devm_rave_sp_version(struct device *dev,
                                        struct rave_sp_version *version)
{
        /*
         * NOTE: The format string below uses %02d to display u16
         * intentionally for the sake of backwards compatibility with
         * legacy software.
         */
        return devm_kasprintf(dev, GFP_KERNEL, "%02d%02d%02d.%c%c\n",
                              version->hardware,
                              le16_to_cpu(version->major),
                              version->minor,
                              version->letter[0],
                              version->letter[1]);
}

static int rave_sp_rdu1_get_status(struct rave_sp *sp,
                                   struct rave_sp_status *status)
{
        u8 cmd[] = {
                [0] = RAVE_SP_CMD_STATUS,
                [1] = 0
        };

        return rave_sp_exec(sp, cmd, sizeof(cmd), status, sizeof(*status));
}

static int rave_sp_emulated_get_status(struct rave_sp *sp,
                                       struct rave_sp_status *status)
{
        u8 cmd[] = {
                [0] = RAVE_SP_CMD_GET_FIRMWARE_VERSION,
                [1] = 0,
        };
        int ret;

        ret = rave_sp_exec(sp, cmd, sizeof(cmd), &status->firmware_version,
                           sizeof(status->firmware_version));
        if (ret)
                return ret;

        cmd[0] = RAVE_SP_CMD_GET_BOOTLOADER_VERSION;
        return rave_sp_exec(sp, cmd, sizeof(cmd), &status->bootloader_version,
                            sizeof(status->bootloader_version));
}

static int rave_sp_get_status(struct rave_sp *sp)
{
        struct device *dev = &sp->serdev->dev;
        struct rave_sp_status status;
        const char *version;
        int ret;

        ret = sp->variant->cmd.get_status(sp, &status);
        if (ret)
                return ret;

        version = devm_rave_sp_version(dev, &status.firmware_version);
        if (!version)
                return -ENOMEM;

        sp->part_number_firmware = version;

        version = devm_rave_sp_version(dev, &status.bootloader_version);
        if (!version)
                return -ENOMEM;

        sp->part_number_bootloader = version;

        return 0;
}

static const struct rave_sp_checksum rave_sp_checksum_8b2c = {
        .length     = 1,
        .subroutine = csum_8b2c,
};

static const struct rave_sp_checksum rave_sp_checksum_ccitt = {
        .length     = 2,
        .subroutine = csum_ccitt,
};

static const struct rave_sp_variant rave_sp_legacy = {
        .checksum = &rave_sp_checksum_ccitt,
        .cmd = {
                .translate = rave_sp_default_cmd_translate,
                .get_status = rave_sp_emulated_get_status,
        },
};

static const struct rave_sp_variant rave_sp_rdu1 = {
        .checksum = &rave_sp_checksum_8b2c,
        .cmd = {
                .translate = rave_sp_rdu1_cmd_translate,
                .get_status = rave_sp_rdu1_get_status,
        },
};

static const struct rave_sp_variant rave_sp_rdu2 = {
        .checksum = &rave_sp_checksum_ccitt,
        .cmd = {
                .translate = rave_sp_rdu2_cmd_translate,
                .get_status = rave_sp_emulated_get_status,
        },
};

static const struct of_device_id rave_sp_dt_ids[] = {
        { .compatible = "zii,rave-sp-niu",  .data = &rave_sp_legacy },
        { .compatible = "zii,rave-sp-mezz", .data = &rave_sp_legacy },
        { .compatible = "zii,rave-sp-esb",  .data = &rave_sp_legacy },
        { .compatible = "zii,rave-sp-rdu1", .data = &rave_sp_rdu1   },
        { .compatible = "zii,rave-sp-rdu2", .data = &rave_sp_rdu2   },
        { /* sentinel */ }
};

static const struct serdev_device_ops rave_sp_serdev_device_ops = {
        .receive_buf  = rave_sp_receive_buf,
        .write_wakeup = serdev_device_write_wakeup,
};

static int rave_sp_probe(struct serdev_device *serdev)
{
        struct device *dev = &serdev->dev;
        const char *unknown = "unknown\n";
        struct rave_sp *sp;
        u32 baud;
        int ret;

        if (of_property_read_u32(dev->of_node, "current-speed", &baud)) {
                dev_err(dev,
                        "'current-speed' is not specified in device node\n");
                return -EINVAL;
        }

        sp = devm_kzalloc(dev, sizeof(*sp), GFP_KERNEL);
        if (!sp)
                return -ENOMEM;

        sp->serdev = serdev;
        dev_set_drvdata(dev, sp);

        sp->variant = of_device_get_match_data(dev);
        if (!sp->variant)
                return -ENODEV;

        mutex_init(&sp->bus_lock);
        mutex_init(&sp->reply_lock);
        BLOCKING_INIT_NOTIFIER_HEAD(&sp->event_notifier_list);

        serdev_device_set_client_ops(serdev, &rave_sp_serdev_device_ops);
        ret = devm_serdev_device_open(dev, serdev);
        if (ret)
                return ret;

        serdev_device_set_baudrate(serdev, baud);
        serdev_device_set_flow_control(serdev, false);

        ret = serdev_device_set_parity(serdev, SERDEV_PARITY_NONE);
        if (ret) {
                dev_err(dev, "Failed to set parity\n");
                return ret;
        }

        ret = rave_sp_get_status(sp);
        if (ret) {
                dev_warn(dev, "Failed to get firmware status: %d\n", ret);
                sp->part_number_firmware   = unknown;
                sp->part_number_bootloader = unknown;
        }

        /*
         * Those strings already have a \n embedded, so there's no
         * need to have one in format string.
         */
        dev_info(dev, "Firmware version: %s",   sp->part_number_firmware);
        dev_info(dev, "Bootloader version: %s", sp->part_number_bootloader);

        return devm_of_platform_populate(dev);
}

MODULE_DEVICE_TABLE(of, rave_sp_dt_ids);

static struct serdev_device_driver rave_sp_drv = {
        .probe                  = rave_sp_probe,
        .driver = {
                .name           = "rave-sp",
                .of_match_table = rave_sp_dt_ids,
        },
};
module_serdev_device_driver(rave_sp_drv);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Andrey Vostrikov <andrey.vostrikov@cogentembedded.com>");
MODULE_AUTHOR("Nikita Yushchenko <nikita.yoush@cogentembedded.com>");
MODULE_AUTHOR("Andrey Smirnov <andrew.smirnov@gmail.com>");
MODULE_DESCRIPTION("RAVE SP core driver");