// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *    Support for NXT2002 and NXT2004 - VSB/QAM
 *
 *    Copyright (C) 2005 Kirk Lapray <kirk.lapray@gmail.com>
 *    Copyright (C) 2006-2014 Michael Krufky <mkrufky@linuxtv.org>
 *    based on nxt2002 by Taylor Jacob <rtjacob@earthlink.net>
 *    and nxt2004 by Jean-Francois Thibert <jeanfrancois@sagetv.com>
*/

/*
 *                      NOTES ABOUT THIS DRIVER
 *
 * This Linux driver supports:
 *   B2C2/BBTI Technisat Air2PC - ATSC (NXT2002)
 *   AverTVHD MCE A180 (NXT2004)
 *   ATI HDTV Wonder (NXT2004)
 *
 * This driver needs external firmware. Please use the command
 * "<kerneldir>/scripts/get_dvb_firmware nxt2002" or
 * "<kerneldir>/scripts/get_dvb_firmware nxt2004" to
 * download/extract the appropriate firmware, and then copy it to
 * /usr/lib/hotplug/firmware/ or /lib/firmware/
 * (depending on configuration of firmware hotplug).
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

/* Max transfer size done by I2C transfer functions */
#define MAX_XFER_SIZE  256

#define NXT2002_DEFAULT_FIRMWARE "dvb-fe-nxt2002.fw"
#define NXT2004_DEFAULT_FIRMWARE "dvb-fe-nxt2004.fw"
#define CRC_CCIT_MASK 0x1021

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>

#include <media/dvb_frontend.h>
#include "nxt200x.h"

struct nxt200x_state {

        struct i2c_adapter* i2c;
        const struct nxt200x_config* config;
        struct dvb_frontend frontend;

        /* demodulator private data */
        nxt_chip_type demod_chip;
        u8 initialised:1;
};

static int debug;
#define dprintk(args...)        do { if (debug) pr_debug(args); } while (0)

static int i2c_writebytes (struct nxt200x_state* state, u8 addr, u8 *buf, u8 len)
{
        int err;
        struct i2c_msg msg = { .addr = addr, .flags = 0, .buf = buf, .len = len };

        if ((err = i2c_transfer (state->i2c, &msg, 1)) != 1) {
                pr_warn("%s: i2c write error (addr 0x%02x, err == %i)\n",
                        __func__, addr, err);
                return -EREMOTEIO;
        }
        return 0;
}

static int i2c_readbytes(struct nxt200x_state *state, u8 addr, u8 *buf, u8 len)
{
        int err;
        struct i2c_msg msg = { .addr = addr, .flags = I2C_M_RD, .buf = buf, .len = len };

        if ((err = i2c_transfer (state->i2c, &msg, 1)) != 1) {
                pr_warn("%s: i2c read error (addr 0x%02x, err == %i)\n",
                        __func__, addr, err);
                return -EREMOTEIO;
        }
        return 0;
}

static int nxt200x_writebytes (struct nxt200x_state* state, u8 reg,
                               const u8 *buf, u8 len)
{
        u8 buf2[MAX_XFER_SIZE];
        int err;
        struct i2c_msg msg = { .addr = state->config->demod_address, .flags = 0, .buf = buf2, .len = len + 1 };

        if (1 + len > sizeof(buf2)) {
                pr_warn("%s: i2c wr reg=%04x: len=%d is too big!\n",
                         __func__, reg, len);
                return -EINVAL;
        }

        buf2[0] = reg;
        memcpy(&buf2[1], buf, len);

        if ((err = i2c_transfer (state->i2c, &msg, 1)) != 1) {
                pr_warn("%s: i2c write error (addr 0x%02x, err == %i)\n",
                        __func__, state->config->demod_address, err);
                return -EREMOTEIO;
        }
        return 0;
}

static int nxt200x_readbytes(struct nxt200x_state *state, u8 reg, u8 *buf, u8 len)
{
        u8 reg2 [] = { reg };

        struct i2c_msg msg [] = { { .addr = state->config->demod_address, .flags = 0, .buf = reg2, .len = 1 },
                        { .addr = state->config->demod_address, .flags = I2C_M_RD, .buf = buf, .len = len } };

        int err;

        if ((err = i2c_transfer (state->i2c, msg, 2)) != 2) {
                pr_warn("%s: i2c read error (addr 0x%02x, err == %i)\n",
                        __func__, state->config->demod_address, err);
                return -EREMOTEIO;
        }
        return 0;
}

static u16 nxt200x_crc(u16 crc, u8 c)
{
        u8 i;
        u16 input = (u16) c & 0xFF;

        input<<=8;
        for(i=0; i<8; i++) {
                if((crc^input) & 0x8000)
                        crc=(crc<<1)^CRC_CCIT_MASK;
                else
                        crc<<=1;
                input<<=1;
        }
        return crc;
}

static int nxt200x_writereg_multibyte (struct nxt200x_state* state, u8 reg, u8* data, u8 len)
{
        u8 attr, len2, buf;
        dprintk("%s\n", __func__);

        /* set multi register register */
        nxt200x_writebytes(state, 0x35, &reg, 1);

        /* send the actual data */
        nxt200x_writebytes(state, 0x36, data, len);

        switch (state->demod_chip) {
                case NXT2002:
                        len2 = len;
                        buf = 0x02;
                        break;
                case NXT2004:
                        /* probably not right, but gives correct values */
                        attr = 0x02;
                        if (reg & 0x80) {
                                attr = attr << 1;
                                if (reg & 0x04)
                                        attr = attr >> 1;
                        }
                        /* set write bit */
                        len2 = ((attr << 4) | 0x10) | len;
                        buf = 0x80;
                        break;
                default:
                        return -EINVAL;
        }

        /* set multi register length */
        nxt200x_writebytes(state, 0x34, &len2, 1);

        /* toggle the multireg write bit */
        nxt200x_writebytes(state, 0x21, &buf, 1);

        nxt200x_readbytes(state, 0x21, &buf, 1);

        switch (state->demod_chip) {
                case NXT2002:
                        if ((buf & 0x02) == 0)
                                return 0;
                        break;
                case NXT2004:
                        if (buf == 0)
                                return 0;
                        break;
                default:
                        return -EINVAL;
        }

        pr_warn("Error writing multireg register 0x%02X\n", reg);

        return 0;
}

static int nxt200x_readreg_multibyte (struct nxt200x_state* state, u8 reg, u8* data, u8 len)
{
        int i;
        u8 buf, len2, attr;
        dprintk("%s\n", __func__);

        /* set multi register register */
        nxt200x_writebytes(state, 0x35, &reg, 1);

        switch (state->demod_chip) {
                case NXT2002:
                        /* set multi register length */
                        len2 = len & 0x80;
                        nxt200x_writebytes(state, 0x34, &len2, 1);

                        /* read the actual data */
                        nxt200x_readbytes(state, reg, data, len);
                        return 0;
                case NXT2004:
                        /* probably not right, but gives correct values */
                        attr = 0x02;
                        if (reg & 0x80) {
                                attr = attr << 1;
                                if (reg & 0x04)
                                        attr = attr >> 1;
                        }

                        /* set multi register length */
                        len2 = (attr << 4) | len;
                        nxt200x_writebytes(state, 0x34, &len2, 1);

                        /* toggle the multireg bit*/
                        buf = 0x80;
                        nxt200x_writebytes(state, 0x21, &buf, 1);

                        /* read the actual data */
                        for(i = 0; i < len; i++) {
                                nxt200x_readbytes(state, 0x36 + i, &data[i], 1);
                        }
                        return 0;
                default:
                        return -EINVAL;
        }
}

static void nxt200x_microcontroller_stop (struct nxt200x_state* state)
{
        u8 buf, stopval, counter = 0;
        dprintk("%s\n", __func__);

        /* set correct stop value */
        switch (state->demod_chip) {
                case NXT2002:
                        stopval = 0x40;
                        break;
                case NXT2004:
                        stopval = 0x10;
                        break;
                default:
                        stopval = 0;
                        break;
        }

        buf = 0x80;
        nxt200x_writebytes(state, 0x22, &buf, 1);

        while (counter < 20) {
                nxt200x_readbytes(state, 0x31, &buf, 1);
                if (buf & stopval)
                        return;
                msleep(10);
                counter++;
        }

        pr_warn("Timeout waiting for nxt200x to stop. This is ok after firmware upload.\n");
        return;
}

static void nxt200x_microcontroller_start (struct nxt200x_state* state)
{
        u8 buf;
        dprintk("%s\n", __func__);

        buf = 0x00;
        nxt200x_writebytes(state, 0x22, &buf, 1);
}

static void nxt2004_microcontroller_init (struct nxt200x_state* state)
{
        u8 buf[9];
        u8 counter = 0;
        dprintk("%s\n", __func__);

        buf[0] = 0x00;
        nxt200x_writebytes(state, 0x2b, buf, 1);
        buf[0] = 0x70;
        nxt200x_writebytes(state, 0x34, buf, 1);
        buf[0] = 0x04;
        nxt200x_writebytes(state, 0x35, buf, 1);
        buf[0] = 0x01; buf[1] = 0x23; buf[2] = 0x45; buf[3] = 0x67; buf[4] = 0x89;
        buf[5] = 0xAB; buf[6] = 0xCD; buf[7] = 0xEF; buf[8] = 0xC0;
        nxt200x_writebytes(state, 0x36, buf, 9);
        buf[0] = 0x80;
        nxt200x_writebytes(state, 0x21, buf, 1);

        while (counter < 20) {
                nxt200x_readbytes(state, 0x21, buf, 1);
                if (buf[0] == 0)
                        return;
                msleep(10);
                counter++;
        }

        pr_warn("Timeout waiting for nxt2004 to init.\n");

        return;
}

static int nxt200x_writetuner (struct nxt200x_state* state, u8* data)
{
        u8 buf, count = 0;

        dprintk("%s\n", __func__);

        dprintk("Tuner Bytes: %*ph\n", 4, data + 1);

        /* if NXT2004, write directly to tuner. if NXT2002, write through NXT chip.
         * direct write is required for Philips TUV1236D and ALPS TDHU2 */
        switch (state->demod_chip) {
                case NXT2004:
                        if (i2c_writebytes(state, data[0], data+1, 4))
                                pr_warn("error writing to tuner\n");
                        /* wait until we have a lock */
                        while (count < 20) {
                                i2c_readbytes(state, data[0], &buf, 1);
                                if (buf & 0x40)
                                        return 0;
                                msleep(100);
                                count++;
                        }
                        pr_warn("timeout waiting for tuner lock\n");
                        break;
                case NXT2002:
                        /* set the i2c transfer speed to the tuner */
                        buf = 0x03;
                        nxt200x_writebytes(state, 0x20, &buf, 1);

                        /* setup to transfer 4 bytes via i2c */
                        buf = 0x04;
                        nxt200x_writebytes(state, 0x34, &buf, 1);

                        /* write actual tuner bytes */
                        nxt200x_writebytes(state, 0x36, data+1, 4);

                        /* set tuner i2c address */
                        buf = data[0] << 1;
                        nxt200x_writebytes(state, 0x35, &buf, 1);

                        /* write UC Opmode to begin transfer */
                        buf = 0x80;
                        nxt200x_writebytes(state, 0x21, &buf, 1);

                        while (count < 20) {
                                nxt200x_readbytes(state, 0x21, &buf, 1);
                                if ((buf & 0x80)== 0x00)
                                        return 0;
                                msleep(100);
                                count++;
                        }
                        pr_warn("timeout error writing to tuner\n");
                        break;
                default:
                        return -EINVAL;
        }
        return 0;
}

static void nxt200x_agc_reset(struct nxt200x_state* state)
{
        u8 buf;
        dprintk("%s\n", __func__);

        switch (state->demod_chip) {
                case NXT2002:
                        buf = 0x08;
                        nxt200x_writebytes(state, 0x08, &buf, 1);
                        buf = 0x00;
                        nxt200x_writebytes(state, 0x08, &buf, 1);
                        break;
                case NXT2004:
                        nxt200x_readreg_multibyte(state, 0x08, &buf, 1);
                        buf = 0x08;
                        nxt200x_writereg_multibyte(state, 0x08, &buf, 1);
                        buf = 0x00;
                        nxt200x_writereg_multibyte(state, 0x08, &buf, 1);
                        break;
                default:
                        break;
        }
        return;
}

static int nxt2002_load_firmware (struct dvb_frontend* fe, const struct firmware *fw)
{

        struct nxt200x_state* state = fe->demodulator_priv;
        u8 buf[3], written = 0, chunkpos = 0;
        u16 rambase, position, crc = 0;

        dprintk("%s\n", __func__);
        dprintk("Firmware is %zu bytes\n", fw->size);

        /* Get the RAM base for this nxt2002 */
        nxt200x_readbytes(state, 0x10, buf, 1);

        if (buf[0] & 0x10)
                rambase = 0x1000;
        else
                rambase = 0x0000;

        dprintk("rambase on this nxt2002 is %04X\n", rambase);

        /* Hold the micro in reset while loading firmware */
        buf[0] = 0x80;
        nxt200x_writebytes(state, 0x2B, buf, 1);

        for (position = 0; position < fw->size; position++) {
                if (written == 0) {
                        crc = 0;
                        chunkpos = 0x28;
                        buf[0] = ((rambase + position) >> 8);
                        buf[1] = (rambase + position) & 0xFF;
                        buf[2] = 0x81;
                        /* write starting address */
                        nxt200x_writebytes(state, 0x29, buf, 3);
                }
                written++;
                chunkpos++;

                if ((written % 4) == 0)
                        nxt200x_writebytes(state, chunkpos, &fw->data[position-3], 4);

                crc = nxt200x_crc(crc, fw->data[position]);

                if ((written == 255) || (position+1 == fw->size)) {
                        /* write remaining bytes of firmware */
                        nxt200x_writebytes(state, chunkpos+4-(written %4),
                                &fw->data[position-(written %4) + 1],
                                written %4);
                        buf[0] = crc << 8;
                        buf[1] = crc & 0xFF;

                        /* write crc */
                        nxt200x_writebytes(state, 0x2C, buf, 2);

                        /* do a read to stop things */
                        nxt200x_readbytes(state, 0x2A, buf, 1);

                        /* set transfer mode to complete */
                        buf[0] = 0x80;
                        nxt200x_writebytes(state, 0x2B, buf, 1);

                        written = 0;
                }
        }

        return 0;
};

static int nxt2004_load_firmware (struct dvb_frontend* fe, const struct firmware *fw)
{

        struct nxt200x_state* state = fe->demodulator_priv;
        u8 buf[3];
        u16 rambase, position, crc=0;

        dprintk("%s\n", __func__);
        dprintk("Firmware is %zu bytes\n", fw->size);

        /* set rambase */
        rambase = 0x1000;

        /* hold the micro in reset while loading firmware */
        buf[0] = 0x80;
        nxt200x_writebytes(state, 0x2B, buf,1);

        /* calculate firmware CRC */
        for (position = 0; position < fw->size; position++) {
                crc = nxt200x_crc(crc, fw->data[position]);
        }

        buf[0] = rambase >> 8;
        buf[1] = rambase & 0xFF;
        buf[2] = 0x81;
        /* write starting address */
        nxt200x_writebytes(state,0x29,buf,3);

        for (position = 0; position < fw->size;) {
                nxt200x_writebytes(state, 0x2C, &fw->data[position],
                        fw->size-position > 255 ? 255 : fw->size-position);
                position += (fw->size-position > 255 ? 255 : fw->size-position);
        }
        buf[0] = crc >> 8;
        buf[1] = crc & 0xFF;

        dprintk("firmware crc is 0x%02X 0x%02X\n", buf[0], buf[1]);

        /* write crc */
        nxt200x_writebytes(state, 0x2C, buf,2);

        /* do a read to stop things */
        nxt200x_readbytes(state, 0x2C, buf, 1);

        /* set transfer mode to complete */
        buf[0] = 0x80;
        nxt200x_writebytes(state, 0x2B, buf,1);

        return 0;
};

static int nxt200x_setup_frontend_parameters(struct dvb_frontend *fe)
{
        struct dtv_frontend_properties *p = &fe->dtv_property_cache;
        struct nxt200x_state* state = fe->demodulator_priv;
        u8 buf[5];

        /* stop the micro first */
        nxt200x_microcontroller_stop(state);

        if (state->demod_chip == NXT2004) {
                /* make sure demod is set to digital */
                buf[0] = 0x04;
                nxt200x_writebytes(state, 0x14, buf, 1);
                buf[0] = 0x00;
                nxt200x_writebytes(state, 0x17, buf, 1);
        }

        /* set additional params */
        switch (p->modulation) {
                case QAM_64:
                case QAM_256:
                        /* Set punctured clock for QAM */
                        /* This is just a guess since I am unable to test it */
                        if (state->config->set_ts_params)
                                state->config->set_ts_params(fe, 1);
                        break;
                case VSB_8:
                        /* Set non-punctured clock for VSB */
                        if (state->config->set_ts_params)
                                state->config->set_ts_params(fe, 0);
                        break;
                default:
                        return -EINVAL;
        }

        if (fe->ops.tuner_ops.calc_regs) {
                /* get tuning information */
                fe->ops.tuner_ops.calc_regs(fe, buf, 5);

                /* write frequency information */
                nxt200x_writetuner(state, buf);
        }

        /* reset the agc now that tuning has been completed */
        nxt200x_agc_reset(state);

        /* set target power level */
        switch (p->modulation) {
                case QAM_64:
                case QAM_256:
                        buf[0] = 0x74;
                        break;
                case VSB_8:
                        buf[0] = 0x70;
                        break;
                default:
                        return -EINVAL;
        }
        nxt200x_writebytes(state, 0x42, buf, 1);

        /* configure sdm */
        switch (state->demod_chip) {
                case NXT2002:
                        buf[0] = 0x87;
                        break;
                case NXT2004:
                        buf[0] = 0x07;
                        break;
                default:
                        return -EINVAL;
        }
        nxt200x_writebytes(state, 0x57, buf, 1);

        /* write sdm1 input */
        buf[0] = 0x10;
        buf[1] = 0x00;
        switch (state->demod_chip) {
                case NXT2002:
                        nxt200x_writereg_multibyte(state, 0x58, buf, 2);
                        break;
                case NXT2004:
                        nxt200x_writebytes(state, 0x58, buf, 2);
                        break;
                default:
                        return -EINVAL;
        }

        /* write sdmx input */
        switch (p->modulation) {
                case QAM_64:
                                buf[0] = 0x68;
                                break;
                case QAM_256:
                                buf[0] = 0x64;
                                break;
                case VSB_8:
                                buf[0] = 0x60;
                                break;
                default:
                                return -EINVAL;
        }
        buf[1] = 0x00;
        switch (state->demod_chip) {
                case NXT2002:
                        nxt200x_writereg_multibyte(state, 0x5C, buf, 2);
                        break;
                case NXT2004:
                        nxt200x_writebytes(state, 0x5C, buf, 2);
                        break;
                default:
                        return -EINVAL;
        }

        /* write adc power lpf fc */
        buf[0] = 0x05;
        nxt200x_writebytes(state, 0x43, buf, 1);

        if (state->demod_chip == NXT2004) {
                /* write ??? */
                buf[0] = 0x00;
                buf[1] = 0x00;
                nxt200x_writebytes(state, 0x46, buf, 2);
        }

        /* write accumulator2 input */
        buf[0] = 0x80;
        buf[1] = 0x00;
        switch (state->demod_chip) {
                case NXT2002:
                        nxt200x_writereg_multibyte(state, 0x4B, buf, 2);
                        break;
                case NXT2004:
                        nxt200x_writebytes(state, 0x4B, buf, 2);
                        break;
                default:
                        return -EINVAL;
        }

        /* write kg1 */
        buf[0] = 0x00;
        nxt200x_writebytes(state, 0x4D, buf, 1);

        /* write sdm12 lpf fc */
        buf[0] = 0x44;
        nxt200x_writebytes(state, 0x55, buf, 1);

        /* write agc control reg */
        buf[0] = 0x04;
        nxt200x_writebytes(state, 0x41, buf, 1);

        if (state->demod_chip == NXT2004) {
                nxt200x_readreg_multibyte(state, 0x80, buf, 1);
                buf[0] = 0x24;
                nxt200x_writereg_multibyte(state, 0x80, buf, 1);

                /* soft reset? */
                nxt200x_readreg_multibyte(state, 0x08, buf, 1);
                buf[0] = 0x10;
                nxt200x_writereg_multibyte(state, 0x08, buf, 1);
                nxt200x_readreg_multibyte(state, 0x08, buf, 1);
                buf[0] = 0x00;
                nxt200x_writereg_multibyte(state, 0x08, buf, 1);

                nxt200x_readreg_multibyte(state, 0x80, buf, 1);
                buf[0] = 0x04;
                nxt200x_writereg_multibyte(state, 0x80, buf, 1);
                buf[0] = 0x00;
                nxt200x_writereg_multibyte(state, 0x81, buf, 1);
                buf[0] = 0x80; buf[1] = 0x00; buf[2] = 0x00;
                nxt200x_writereg_multibyte(state, 0x82, buf, 3);
                nxt200x_readreg_multibyte(state, 0x88, buf, 1);
                buf[0] = 0x11;
                nxt200x_writereg_multibyte(state, 0x88, buf, 1);
                nxt200x_readreg_multibyte(state, 0x80, buf, 1);
                buf[0] = 0x44;
                nxt200x_writereg_multibyte(state, 0x80, buf, 1);
        }

        /* write agc ucgp0 */
        switch (p->modulation) {
                case QAM_64:
                                buf[0] = 0x02;
                                break;
                case QAM_256:
                                buf[0] = 0x03;
                                break;
                case VSB_8:
                                buf[0] = 0x00;
                                break;
                default:
                                return -EINVAL;
        }
        nxt200x_writebytes(state, 0x30, buf, 1);

        /* write agc control reg */
        buf[0] = 0x00;
        nxt200x_writebytes(state, 0x41, buf, 1);

        /* write accumulator2 input */
        buf[0] = 0x80;
        buf[1] = 0x00;
        switch (state->demod_chip) {
                case NXT2002:
                        nxt200x_writereg_multibyte(state, 0x49, buf, 2);
                        nxt200x_writereg_multibyte(state, 0x4B, buf, 2);
                        break;
                case NXT2004:
                        nxt200x_writebytes(state, 0x49, buf, 2);
                        nxt200x_writebytes(state, 0x4B, buf, 2);
                        break;
                default:
                        return -EINVAL;
        }

        /* write agc control reg */
        buf[0] = 0x04;
        nxt200x_writebytes(state, 0x41, buf, 1);

        nxt200x_microcontroller_start(state);

        if (state->demod_chip == NXT2004) {
                nxt2004_microcontroller_init(state);

                /* ???? */
                buf[0] = 0xF0;
                buf[1] = 0x00;
                nxt200x_writebytes(state, 0x5C, buf, 2);
        }

        /* adjacent channel detection should be done here, but I don't
        have any stations with this need so I cannot test it */

        return 0;
}

static int nxt200x_read_status(struct dvb_frontend *fe, enum fe_status *status)
{
        struct nxt200x_state* state = fe->demodulator_priv;
        u8 lock;
        nxt200x_readbytes(state, 0x31, &lock, 1);

        *status = 0;
        if (lock & 0x20) {
                *status |= FE_HAS_SIGNAL;
                *status |= FE_HAS_CARRIER;
                *status |= FE_HAS_VITERBI;
                *status |= FE_HAS_SYNC;
                *status |= FE_HAS_LOCK;
        }
        return 0;
}

static int nxt200x_read_ber(struct dvb_frontend* fe, u32* ber)
{
        struct nxt200x_state* state = fe->demodulator_priv;
        u8 b[3];

        nxt200x_readreg_multibyte(state, 0xE6, b, 3);

        *ber = ((b[0] << 8) + b[1]) * 8;

        return 0;
}

static int nxt200x_read_signal_strength(struct dvb_frontend* fe, u16* strength)
{
        struct nxt200x_state* state = fe->demodulator_priv;
        u8 b[2];
        u16 temp = 0;

        /* setup to read cluster variance */
        b[0] = 0x00;
        nxt200x_writebytes(state, 0xA1, b, 1);

        /* get multreg val */
        nxt200x_readreg_multibyte(state, 0xA6, b, 2);

        temp = (b[0] << 8) | b[1];
        *strength = ((0x7FFF - temp) & 0x0FFF) * 16;

        return 0;
}

static int nxt200x_read_snr(struct dvb_frontend* fe, u16* snr)
{

        struct nxt200x_state* state = fe->demodulator_priv;
        u8 b[2];
        u16 temp = 0, temp2;
        u32 snrdb = 0;

        /* setup to read cluster variance */
        b[0] = 0x00;
        nxt200x_writebytes(state, 0xA1, b, 1);

        /* get multreg val from 0xA6 */
        nxt200x_readreg_multibyte(state, 0xA6, b, 2);

        temp = (b[0] << 8) | b[1];
        temp2 = 0x7FFF - temp;

        /* snr will be in db */
        if (temp2 > 0x7F00)
                snrdb = 1000*24 + ( 1000*(30-24) * ( temp2 - 0x7F00 ) / ( 0x7FFF - 0x7F00 ) );
        else if (temp2 > 0x7EC0)
                snrdb = 1000*18 + ( 1000*(24-18) * ( temp2 - 0x7EC0 ) / ( 0x7F00 - 0x7EC0 ) );
        else if (temp2 > 0x7C00)
                snrdb = 1000*12 + ( 1000*(18-12) * ( temp2 - 0x7C00 ) / ( 0x7EC0 - 0x7C00 ) );
        else
                snrdb = 1000*0 + ( 1000*(12-0) * ( temp2 - 0 ) / ( 0x7C00 - 0 ) );

        /* the value reported back from the frontend will be FFFF=32db 0000=0db */
        *snr = snrdb * (0xFFFF/32000);

        return 0;
}

static int nxt200x_read_ucblocks(struct dvb_frontend* fe, u32* ucblocks)
{
        struct nxt200x_state* state = fe->demodulator_priv;
        u8 b[3];

        nxt200x_readreg_multibyte(state, 0xE6, b, 3);
        *ucblocks = b[2];

        return 0;
}

static int nxt200x_sleep(struct dvb_frontend* fe)
{
        return 0;
}

static int nxt2002_init(struct dvb_frontend* fe)
{
        struct nxt200x_state* state = fe->demodulator_priv;
        const struct firmware *fw;
        int ret;
        u8 buf[2];

        /* request the firmware, this will block until someone uploads it */
        pr_debug("%s: Waiting for firmware upload (%s)...\n",
                 __func__, NXT2002_DEFAULT_FIRMWARE);
        ret = request_firmware(&fw, NXT2002_DEFAULT_FIRMWARE,
                               state->i2c->dev.parent);
        pr_debug("%s: Waiting for firmware upload(2)...\n", __func__);
        if (ret) {
                pr_err("%s: No firmware uploaded (timeout or file not found?)\n",
                       __func__);
                return ret;
        }

        ret = nxt2002_load_firmware(fe, fw);
        release_firmware(fw);
        if (ret) {
                pr_err("%s: Writing firmware to device failed\n", __func__);
                return ret;
        }
        pr_info("%s: Firmware upload complete\n", __func__);

        /* Put the micro into reset */
        nxt200x_microcontroller_stop(state);

        /* ensure transfer is complete */
        buf[0]=0x00;
        nxt200x_writebytes(state, 0x2B, buf, 1);

        /* Put the micro into reset for real this time */
        nxt200x_microcontroller_stop(state);

        /* soft reset everything (agc,frontend,eq,fec)*/
        buf[0] = 0x0F;
        nxt200x_writebytes(state, 0x08, buf, 1);
        buf[0] = 0x00;
        nxt200x_writebytes(state, 0x08, buf, 1);

        /* write agc sdm configure */
        buf[0] = 0xF1;
        nxt200x_writebytes(state, 0x57, buf, 1);

        /* write mod output format */
        buf[0] = 0x20;
        nxt200x_writebytes(state, 0x09, buf, 1);

        /* write fec mpeg mode */
        buf[0] = 0x7E;
        buf[1] = 0x00;
        nxt200x_writebytes(state, 0xE9, buf, 2);

        /* write mux selection */
        buf[0] = 0x00;
        nxt200x_writebytes(state, 0xCC, buf, 1);

        return 0;
}

static int nxt2004_init(struct dvb_frontend* fe)
{
        struct nxt200x_state* state = fe->demodulator_priv;
        const struct firmware *fw;
        int ret;
        u8 buf[3];

        /* ??? */
        buf[0]=0x00;
        nxt200x_writebytes(state, 0x1E, buf, 1);

        /* request the firmware, this will block until someone uploads it */
        pr_debug("%s: Waiting for firmware upload (%s)...\n",
                 __func__, NXT2004_DEFAULT_FIRMWARE);
        ret = request_firmware(&fw, NXT2004_DEFAULT_FIRMWARE,
                               state->i2c->dev.parent);
        pr_debug("%s: Waiting for firmware upload(2)...\n", __func__);
        if (ret) {
                pr_err("%s: No firmware uploaded (timeout or file not found?)\n",
                       __func__);
                return ret;
        }

        ret = nxt2004_load_firmware(fe, fw);
        release_firmware(fw);
        if (ret) {
                pr_err("%s: Writing firmware to device failed\n", __func__);
                return ret;
        }
        pr_info("%s: Firmware upload complete\n", __func__);

        /* ensure transfer is complete */
        buf[0] = 0x01;
        nxt200x_writebytes(state, 0x19, buf, 1);

        nxt2004_microcontroller_init(state);
        nxt200x_microcontroller_stop(state);
        nxt200x_microcontroller_stop(state);
        nxt2004_microcontroller_init(state);
        nxt200x_microcontroller_stop(state);

        /* soft reset everything (agc,frontend,eq,fec)*/
        buf[0] = 0xFF;
        nxt200x_writereg_multibyte(state, 0x08, buf, 1);
        buf[0] = 0x00;
        nxt200x_writereg_multibyte(state, 0x08, buf, 1);

        /* write agc sdm configure */
        buf[0] = 0xD7;
        nxt200x_writebytes(state, 0x57, buf, 1);

        /* ???*/
        buf[0] = 0x07;
        buf[1] = 0xfe;
        nxt200x_writebytes(state, 0x35, buf, 2);
        buf[0] = 0x12;
        nxt200x_writebytes(state, 0x34, buf, 1);
        buf[0] = 0x80;
        nxt200x_writebytes(state, 0x21, buf, 1);

        /* ???*/
        buf[0] = 0x21;
        nxt200x_writebytes(state, 0x0A, buf, 1);

        /* ???*/
        buf[0] = 0x01;
        nxt200x_writereg_multibyte(state, 0x80, buf, 1);

        /* write fec mpeg mode */
        buf[0] = 0x7E;
        buf[1] = 0x00;
        nxt200x_writebytes(state, 0xE9, buf, 2);

        /* write mux selection */
        buf[0] = 0x00;
        nxt200x_writebytes(state, 0xCC, buf, 1);

        /* ???*/
        nxt200x_readreg_multibyte(state, 0x80, buf, 1);
        buf[0] = 0x00;
        nxt200x_writereg_multibyte(state, 0x80, buf, 1);

        /* soft reset? */
        nxt200x_readreg_multibyte(state, 0x08, buf, 1);
        buf[0] = 0x10;
        nxt200x_writereg_multibyte(state, 0x08, buf, 1);
        nxt200x_readreg_multibyte(state, 0x08, buf, 1);
        buf[0] = 0x00;
        nxt200x_writereg_multibyte(state, 0x08, buf, 1);

        /* ???*/
        nxt200x_readreg_multibyte(state, 0x80, buf, 1);
        buf[0] = 0x01;
        nxt200x_writereg_multibyte(state, 0x80, buf, 1);
        buf[0] = 0x70;
        nxt200x_writereg_multibyte(state, 0x81, buf, 1);
        buf[0] = 0x31; buf[1] = 0x5E; buf[2] = 0x66;
        nxt200x_writereg_multibyte(state, 0x82, buf, 3);

        nxt200x_readreg_multibyte(state, 0x88, buf, 1);
        buf[0] = 0x11;
        nxt200x_writereg_multibyte(state, 0x88, buf, 1);
        nxt200x_readreg_multibyte(state, 0x80, buf, 1);
        buf[0] = 0x40;
        nxt200x_writereg_multibyte(state, 0x80, buf, 1);

        nxt200x_readbytes(state, 0x10, buf, 1);
        buf[0] = 0x10;
        nxt200x_writebytes(state, 0x10, buf, 1);
        nxt200x_readbytes(state, 0x0A, buf, 1);
        buf[0] = 0x21;
        nxt200x_writebytes(state, 0x0A, buf, 1);

        nxt2004_microcontroller_init(state);

        buf[0] = 0x21;
        nxt200x_writebytes(state, 0x0A, buf, 1);
        buf[0] = 0x7E;
        nxt200x_writebytes(state, 0xE9, buf, 1);
        buf[0] = 0x00;
        nxt200x_writebytes(state, 0xEA, buf, 1);

        nxt200x_readreg_multibyte(state, 0x80, buf, 1);
        buf[0] = 0x00;
        nxt200x_writereg_multibyte(state, 0x80, buf, 1);
        nxt200x_readreg_multibyte(state, 0x80, buf, 1);
        buf[0] = 0x00;
        nxt200x_writereg_multibyte(state, 0x80, buf, 1);

        /* soft reset? */
        nxt200x_readreg_multibyte(state, 0x08, buf, 1);
        buf[0] = 0x10;
        nxt200x_writereg_multibyte(state, 0x08, buf, 1);
        nxt200x_readreg_multibyte(state, 0x08, buf, 1);
        buf[0] = 0x00;
        nxt200x_writereg_multibyte(state, 0x08, buf, 1);

        nxt200x_readreg_multibyte(state, 0x80, buf, 1);
        buf[0] = 0x04;
        nxt200x_writereg_multibyte(state, 0x80, buf, 1);
        buf[0] = 0x00;
        nxt200x_writereg_multibyte(state, 0x81, buf, 1);
        buf[0] = 0x80; buf[1] = 0x00; buf[2] = 0x00;
        nxt200x_writereg_multibyte(state, 0x82, buf, 3);

        nxt200x_readreg_multibyte(state, 0x88, buf, 1);
        buf[0] = 0x11;
        nxt200x_writereg_multibyte(state, 0x88, buf, 1);

        nxt200x_readreg_multibyte(state, 0x80, buf, 1);
        buf[0] = 0x44;
        nxt200x_writereg_multibyte(state, 0x80, buf, 1);

        /* initialize tuner */
        nxt200x_readbytes(state, 0x10, buf, 1);
        buf[0] = 0x12;
        nxt200x_writebytes(state, 0x10, buf, 1);
        buf[0] = 0x04;
        nxt200x_writebytes(state, 0x13, buf, 1);
        buf[0] = 0x00;
        nxt200x_writebytes(state, 0x16, buf, 1);
        buf[0] = 0x04;
        nxt200x_writebytes(state, 0x14, buf, 1);
        buf[0] = 0x00;
        nxt200x_writebytes(state, 0x14, buf, 1);
        nxt200x_writebytes(state, 0x17, buf, 1);
        nxt200x_writebytes(state, 0x14, buf, 1);
        nxt200x_writebytes(state, 0x17, buf, 1);

        return 0;
}

static int nxt200x_init(struct dvb_frontend* fe)
{
        struct nxt200x_state* state = fe->demodulator_priv;
        int ret = 0;

        if (!state->initialised) {
                switch (state->demod_chip) {
                        case NXT2002:
                                ret = nxt2002_init(fe);
                                break;
                        case NXT2004:
                                ret = nxt2004_init(fe);
                                break;
                        default:
                                return -EINVAL;
                }
                state->initialised = 1;
        }
        return ret;
}

static int nxt200x_get_tune_settings(struct dvb_frontend* fe, struct dvb_frontend_tune_settings* fesettings)
{
        fesettings->min_delay_ms = 500;
        fesettings->step_size = 0;
        fesettings->max_drift = 0;
        return 0;
}

static void nxt200x_release(struct dvb_frontend* fe)
{
        struct nxt200x_state* state = fe->demodulator_priv;
        kfree(state);
}

static const struct dvb_frontend_ops nxt200x_ops;

struct dvb_frontend* nxt200x_attach(const struct nxt200x_config* config,
                                   struct i2c_adapter* i2c)
{
        struct nxt200x_state* state = NULL;
        u8 buf [] = {0,0,0,0,0};

        /* allocate memory for the internal state */
        state = kzalloc_obj(struct nxt200x_state);
        if (state == NULL)
                goto error;

        /* setup the state */
        state->config = config;
        state->i2c = i2c;
        state->initialised = 0;

        /* read card id */
        nxt200x_readbytes(state, 0x00, buf, 5);
        dprintk("NXT info: %*ph\n", 5, buf);

        /* set demod chip */
        switch (buf[0]) {
                case 0x04:
                        state->demod_chip = NXT2002;
                        pr_info("NXT2002 Detected\n");
                        break;
                case 0x05:
                        state->demod_chip = NXT2004;
                        pr_info("NXT2004 Detected\n");
                        break;
                default:
                        goto error;
        }

        /* make sure demod chip is supported */
        switch (state->demod_chip) {
                case NXT2002:
                        if (buf[0] != 0x04) goto error;         /* device id */
                        if (buf[1] != 0x02) goto error;         /* fab id */
                        if (buf[2] != 0x11) goto error;         /* month */
                        if (buf[3] != 0x20) goto error;         /* year msb */
                        if (buf[4] != 0x00) goto error;         /* year lsb */
                        break;
                case NXT2004:
                        if (buf[0] != 0x05) goto error;         /* device id */
                        break;
                default:
                        goto error;
        }

        /* create dvb_frontend */
        memcpy(&state->frontend.ops, &nxt200x_ops, sizeof(struct dvb_frontend_ops));
        state->frontend.demodulator_priv = state;
        return &state->frontend;

error:
        kfree(state);
        pr_err("Unknown/Unsupported NXT chip: %*ph\n", 5, buf);
        return NULL;
}

static const struct dvb_frontend_ops nxt200x_ops = {
        .delsys = { SYS_ATSC, SYS_DVBC_ANNEX_B },
        .info = {
                .name = "Nextwave NXT200X VSB/QAM frontend",
                .frequency_min_hz =  54 * MHz,
                .frequency_max_hz = 860 * MHz,
                .frequency_stepsize_hz = 166666,        /* stepsize is just a guess */
                .caps = FE_CAN_FEC_1_2 | FE_CAN_FEC_2_3 | FE_CAN_FEC_3_4 |
                        FE_CAN_FEC_5_6 | FE_CAN_FEC_7_8 | FE_CAN_FEC_AUTO |
                        FE_CAN_8VSB | FE_CAN_QAM_64 | FE_CAN_QAM_256
        },

        .release = nxt200x_release,

        .init = nxt200x_init,
        .sleep = nxt200x_sleep,

        .set_frontend = nxt200x_setup_frontend_parameters,
        .get_tune_settings = nxt200x_get_tune_settings,

        .read_status = nxt200x_read_status,
        .read_ber = nxt200x_read_ber,
        .read_signal_strength = nxt200x_read_signal_strength,
        .read_snr = nxt200x_read_snr,
        .read_ucblocks = nxt200x_read_ucblocks,
};

module_param(debug, int, 0644);
MODULE_PARM_DESC(debug, "Turn on/off frontend debugging (default:off).");

MODULE_DESCRIPTION("NXT200X (ATSC 8VSB & ITU-T J.83 AnnexB 64/256 QAM) Demodulator Driver");
MODULE_AUTHOR("Kirk Lapray, Michael Krufky, Jean-Francois Thibert, and Taylor Jacob");
MODULE_LICENSE("GPL");

EXPORT_SYMBOL_GPL(nxt200x_attach);