// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * parport-to-butterfly adapter
 *
 * Copyright (C) 2005 David Brownell
 */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/parport.h>

#include <linux/sched.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi_bitbang.h>
#include <linux/spi/flash.h>

#include <linux/mtd/partitions.h>

/*
 * This uses SPI to talk with an "AVR Butterfly", which is a $US20 card
 * with a battery powered AVR microcontroller and lots of goodies.  You
 * can use GCC to develop firmware for this.
 *
 * See Documentation/spi/butterfly.rst for information about how to build
 * and use this custom parallel port cable.
 */

/* DATA output bits (pins 2..9 == D0..D7) */
#define butterfly_nreset (1 << 1)               /* pin 3 */

#define spi_sck_bit     (1 << 0)                /* pin 2 */
#define spi_mosi_bit    (1 << 7)                /* pin 9 */

#define vcc_bits        ((1 << 6) | (1 << 5))   /* pins 7, 8 */

/* STATUS input bits */
#define spi_miso_bit    PARPORT_STATUS_BUSY     /* pin 11 */

/* CONTROL output bits */
#define spi_cs_bit      PARPORT_CONTROL_SELECT  /* pin 17 */

static inline struct butterfly *spidev_to_pp(struct spi_device *spi)
{
        return spi->controller_data;
}

struct butterfly {
        /* REVISIT ... for now, this must be first */
        struct spi_bitbang      bitbang;

        struct parport          *port;
        struct pardevice        *pd;

        u8                      lastbyte;

        struct spi_device       *dataflash;
        struct spi_device       *butterfly;
        struct spi_board_info   info[2];

};

/*----------------------------------------------------------------------*/

static inline void
setsck(struct spi_device *spi, int is_on)
{
        struct butterfly        *pp = spidev_to_pp(spi);
        u8                      bit, byte = pp->lastbyte;

        bit = spi_sck_bit;

        if (is_on)
                byte |= bit;
        else
                byte &= ~bit;
        parport_write_data(pp->port, byte);
        pp->lastbyte = byte;
}

static inline void
setmosi(struct spi_device *spi, int is_on)
{
        struct butterfly        *pp = spidev_to_pp(spi);
        u8                      bit, byte = pp->lastbyte;

        bit = spi_mosi_bit;

        if (is_on)
                byte |= bit;
        else
                byte &= ~bit;
        parport_write_data(pp->port, byte);
        pp->lastbyte = byte;
}

static inline int getmiso(struct spi_device *spi)
{
        struct butterfly        *pp = spidev_to_pp(spi);
        int                     value;
        u8                      bit;

        bit = spi_miso_bit;

        /* only STATUS_BUSY is NOT negated */
        value = !(parport_read_status(pp->port) & bit);
        return (bit == PARPORT_STATUS_BUSY) ? value : !value;
}

static void butterfly_chipselect(struct spi_device *spi, int value)
{
        struct butterfly        *pp = spidev_to_pp(spi);

        /* set default clock polarity */
        if (value != BITBANG_CS_INACTIVE)
                setsck(spi, spi->mode & SPI_CPOL);

        /* here, value == "activate or not";
         * most PARPORT_CONTROL_* bits are negated, so we must
         * morph it to value == "bit value to write in control register"
         */
        if (spi_cs_bit == PARPORT_CONTROL_INIT)
                value = !value;

        parport_frob_control(pp->port, spi_cs_bit, value ? spi_cs_bit : 0);
}

/* we only needed to implement one mode here, and choose SPI_MODE_0 */

#define spidelay(X)     do { } while (0)
/* #define spidelay     ndelay */

#include "spi-bitbang-txrx.h"

static u32
butterfly_txrx_word_mode0(struct spi_device *spi, unsigned nsecs, u32 word,
                          u8 bits, unsigned flags)
{
        return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits);
}

/*----------------------------------------------------------------------*/

/* override default partitioning with cmdlinepart */
static struct mtd_partition partitions[] = { {
        /* JFFS2 wants partitions of 4*N blocks for this device,
         * so sectors 0 and 1 can't be partitions by themselves.
         */

        /* sector 0 = 8 pages * 264 bytes/page (1 block)
         * sector 1 = 248 pages * 264 bytes/page
         */
        .name           = "bookkeeping",        /* 66 KB */
        .offset         = 0,
        .size           = (8 + 248) * 264,
        /* .mask_flags  = MTD_WRITEABLE, */
}, {
        /* sector 2 = 256 pages * 264 bytes/page
         * sectors 3-5 = 512 pages * 264 bytes/page
         */
        .name           = "filesystem",         /* 462 KB */
        .offset         = MTDPART_OFS_APPEND,
        .size           = MTDPART_SIZ_FULL,
} };

static struct flash_platform_data flash = {
        .name           = "butterflash",
        .parts          = partitions,
        .nr_parts       = ARRAY_SIZE(partitions),
};

/* REVISIT remove this ugly global and its "only one" limitation */
static struct butterfly *butterfly;

static void butterfly_attach(struct parport *p)
{
        struct pardevice        *pd;
        int                     status;
        struct butterfly        *pp;
        struct spi_master       *master;
        struct device           *dev = p->physport->dev;
        struct pardev_cb        butterfly_cb;

        if (butterfly || !dev)
                return;

        /* REVISIT:  this just _assumes_ a butterfly is there ... no probe,
         * and no way to be selective about what it binds to.
         */

        master = spi_alloc_master(dev, sizeof(*pp));
        if (!master) {
                status = -ENOMEM;
                goto done;
        }
        pp = spi_master_get_devdata(master);

        /*
         * SPI and bitbang hookup
         *
         * use default setup(), cleanup(), and transfer() methods; and
         * only bother implementing mode 0.  Start it later.
         */
        master->bus_num = 42;
        master->num_chipselect = 2;

        pp->bitbang.master = master;
        pp->bitbang.chipselect = butterfly_chipselect;
        pp->bitbang.txrx_word[SPI_MODE_0] = butterfly_txrx_word_mode0;

        /*
         * parport hookup
         */
        pp->port = p;
        memset(&butterfly_cb, 0, sizeof(butterfly_cb));
        butterfly_cb.private = pp;
        pd = parport_register_dev_model(p, "spi_butterfly", &butterfly_cb, 0);
        if (!pd) {
                status = -ENOMEM;
                goto clean0;
        }
        pp->pd = pd;

        status = parport_claim(pd);
        if (status < 0)
                goto clean1;

        /*
         * Butterfly reset, powerup, run firmware
         */
        pr_debug("%s: powerup/reset Butterfly\n", p->name);

        /* nCS for dataflash (this bit is inverted on output) */
        parport_frob_control(pp->port, spi_cs_bit, 0);

        /* stabilize power with chip in reset (nRESET), and
         * spi_sck_bit clear (CPOL=0)
         */
        pp->lastbyte |= vcc_bits;
        parport_write_data(pp->port, pp->lastbyte);
        msleep(5);

        /* take it out of reset; assume long reset delay */
        pp->lastbyte |= butterfly_nreset;
        parport_write_data(pp->port, pp->lastbyte);
        msleep(100);

        /*
         * Start SPI ... for now, hide that we're two physical busses.
         */
        status = spi_bitbang_start(&pp->bitbang);
        if (status < 0)
                goto clean2;

        /* Bus 1 lets us talk to at45db041b (firmware disables AVR SPI), AVR
         * (firmware resets at45, acts as spi slave) or neither (we ignore
         * both, AVR uses AT45).  Here we expect firmware for the first option.
         */

        pp->info[0].max_speed_hz = 15 * 1000 * 1000;
        strcpy(pp->info[0].modalias, "mtd_dataflash");
        pp->info[0].platform_data = &flash;
        pp->info[0].chip_select = 1;
        pp->info[0].controller_data = pp;
        pp->dataflash = spi_new_device(pp->bitbang.master, &pp->info[0]);
        if (pp->dataflash)
                pr_debug("%s: dataflash at %s\n", p->name,
                         dev_name(&pp->dataflash->dev));

        pr_info("%s: AVR Butterfly\n", p->name);
        butterfly = pp;
        return;

clean2:
        /* turn off VCC */
        parport_write_data(pp->port, 0);

        parport_release(pp->pd);
clean1:
        parport_unregister_device(pd);
clean0:
        spi_master_put(pp->bitbang.master);
done:
        pr_debug("%s: butterfly probe, fail %d\n", p->name, status);
}

static void butterfly_detach(struct parport *p)
{
        struct butterfly        *pp;

        /* FIXME this global is ugly ... but, how to quickly get from
         * the parport to the "struct butterfly" associated with it?
         * "old school" driver-internal device lists?
         */
        if (!butterfly || butterfly->port != p)
                return;
        pp = butterfly;
        butterfly = NULL;

        /* stop() unregisters child devices too */
        spi_bitbang_stop(&pp->bitbang);

        /* turn off VCC */
        parport_write_data(pp->port, 0);
        msleep(10);

        parport_release(pp->pd);
        parport_unregister_device(pp->pd);

        spi_master_put(pp->bitbang.master);
}

static struct parport_driver butterfly_driver = {
        .name =         "spi_butterfly",
        .match_port =   butterfly_attach,
        .detach =       butterfly_detach,
        .devmodel = true,
};
module_parport_driver(butterfly_driver);

MODULE_DESCRIPTION("Parport Adapter driver for AVR Butterfly");
MODULE_LICENSE("GPL");