// SPDX-License-Identifier: GPL-2.0+
/*
 * comedi/drivers/mite.c
 * Hardware driver for NI Mite PCI interface chip
 *
 * COMEDI - Linux Control and Measurement Device Interface
 * Copyright (C) 1997-2002 David A. Schleef <ds@schleef.org>
 */

/*
 * The PCI-MIO E series driver was originally written by
 * Tomasz Motylewski <...>, and ported to comedi by ds.
 *
 * References for specifications:
 *
 *    321747b.pdf  Register Level Programmer Manual (obsolete)
 *    321747c.pdf  Register Level Programmer Manual (new)
 *    DAQ-STC reference manual
 *
 * Other possibly relevant info:
 *
 *    320517c.pdf  User manual (obsolete)
 *    320517f.pdf  User manual (new)
 *    320889a.pdf  delete
 *    320906c.pdf  maximum signal ratings
 *    321066a.pdf  about 16x
 *    321791a.pdf  discontinuation of at-mio-16e-10 rev. c
 *    321808a.pdf  about at-mio-16e-10 rev P
 *    321837a.pdf  discontinuation of at-mio-16de-10 rev d
 *    321838a.pdf  about at-mio-16de-10 rev N
 *
 * ISSUES:
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/log2.h>

#include "../comedi_pci.h"

#include "mite.h"

/*
 * Mite registers
 */
#define MITE_UNKNOWN_DMA_BURST_REG      0x28
#define UNKNOWN_DMA_BURST_ENABLE_BITS   0x600

#define MITE_PCI_CONFIG_OFFSET  0x300
#define MITE_CSIGR              0x460                   /* chip signature */
#define CSIGR_TO_IOWINS(x)      (((x) >> 29) & 0x7)
#define CSIGR_TO_WINS(x)        (((x) >> 24) & 0x1f)
#define CSIGR_TO_WPDEP(x)       (((x) >> 20) & 0x7)
#define CSIGR_TO_DMAC(x)        (((x) >> 16) & 0xf)
#define CSIGR_TO_IMODE(x)       (((x) >> 12) & 0x3)     /* pci=0x3 */
#define CSIGR_TO_MMODE(x)       (((x) >> 8) & 0x3)      /* minimite=1 */
#define CSIGR_TO_TYPE(x)        (((x) >> 4) & 0xf)      /* mite=0, minimite=1 */
#define CSIGR_TO_VER(x)         (((x) >> 0) & 0xf)

#define MITE_CHAN(x)            (0x500 + 0x100 * (x))
#define MITE_CHOR(x)            (0x00 + MITE_CHAN(x))   /* channel operation */
#define CHOR_DMARESET           BIT(31)
#define CHOR_SET_SEND_TC        BIT(11)
#define CHOR_CLR_SEND_TC        BIT(10)
#define CHOR_SET_LPAUSE         BIT(9)
#define CHOR_CLR_LPAUSE         BIT(8)
#define CHOR_CLRDONE            BIT(7)
#define CHOR_CLRRB              BIT(6)
#define CHOR_CLRLC              BIT(5)
#define CHOR_FRESET             BIT(4)
#define CHOR_ABORT              BIT(3)  /* stop without emptying fifo */
#define CHOR_STOP               BIT(2)  /* stop after emptying fifo */
#define CHOR_CONT               BIT(1)
#define CHOR_START              BIT(0)
#define MITE_CHCR(x)            (0x04 + MITE_CHAN(x))   /* channel control */
#define CHCR_SET_DMA_IE         BIT(31)
#define CHCR_CLR_DMA_IE         BIT(30)
#define CHCR_SET_LINKP_IE       BIT(29)
#define CHCR_CLR_LINKP_IE       BIT(28)
#define CHCR_SET_SAR_IE         BIT(27)
#define CHCR_CLR_SAR_IE         BIT(26)
#define CHCR_SET_DONE_IE        BIT(25)
#define CHCR_CLR_DONE_IE        BIT(24)
#define CHCR_SET_MRDY_IE        BIT(23)
#define CHCR_CLR_MRDY_IE        BIT(22)
#define CHCR_SET_DRDY_IE        BIT(21)
#define CHCR_CLR_DRDY_IE        BIT(20)
#define CHCR_SET_LC_IE          BIT(19)
#define CHCR_CLR_LC_IE          BIT(18)
#define CHCR_SET_CONT_RB_IE     BIT(17)
#define CHCR_CLR_CONT_RB_IE     BIT(16)
#define CHCR_FIFO(x)            (((x) & 0x1) << 15)
#define CHCR_FIFODIS            CHCR_FIFO(1)
#define CHCR_FIFO_ON            CHCR_FIFO(0)
#define CHCR_BURST(x)           (((x) & 0x1) << 14)
#define CHCR_BURSTEN            CHCR_BURST(1)
#define CHCR_NO_BURSTEN         CHCR_BURST(0)
#define CHCR_BYTE_SWAP_DEVICE   BIT(6)
#define CHCR_BYTE_SWAP_MEMORY   BIT(4)
#define CHCR_DIR(x)             (((x) & 0x1) << 3)
#define CHCR_DEV_TO_MEM         CHCR_DIR(1)
#define CHCR_MEM_TO_DEV         CHCR_DIR(0)
#define CHCR_MODE(x)            (((x) & 0x7) << 0)
#define CHCR_NORMAL             CHCR_MODE(0)
#define CHCR_CONTINUE           CHCR_MODE(1)
#define CHCR_RINGBUFF           CHCR_MODE(2)
#define CHCR_LINKSHORT          CHCR_MODE(4)
#define CHCR_LINKLONG           CHCR_MODE(5)
#define MITE_TCR(x)             (0x08 + MITE_CHAN(x))   /* transfer count */
#define MITE_MCR(x)             (0x0c + MITE_CHAN(x))   /* memory config */
#define MITE_MAR(x)             (0x10 + MITE_CHAN(x))   /* memory address */
#define MITE_DCR(x)             (0x14 + MITE_CHAN(x))   /* device config */
#define DCR_NORMAL              BIT(29)
#define MITE_DAR(x)             (0x18 + MITE_CHAN(x))   /* device address */
#define MITE_LKCR(x)            (0x1c + MITE_CHAN(x))   /* link config */
#define MITE_LKAR(x)            (0x20 + MITE_CHAN(x))   /* link address */
#define MITE_LLKAR(x)           (0x24 + MITE_CHAN(x))   /* see tnt5002 manual */
#define MITE_BAR(x)             (0x28 + MITE_CHAN(x))   /* base address */
#define MITE_BCR(x)             (0x2c + MITE_CHAN(x))   /* base count */
#define MITE_SAR(x)             (0x30 + MITE_CHAN(x))   /* ? address */
#define MITE_WSCR(x)            (0x34 + MITE_CHAN(x))   /* ? */
#define MITE_WSER(x)            (0x38 + MITE_CHAN(x))   /* ? */
#define MITE_CHSR(x)            (0x3c + MITE_CHAN(x))   /* channel status */
#define CHSR_INT                BIT(31)
#define CHSR_LPAUSES            BIT(29)
#define CHSR_SARS               BIT(27)
#define CHSR_DONE               BIT(25)
#define CHSR_MRDY               BIT(23)
#define CHSR_DRDY               BIT(21)
#define CHSR_LINKC              BIT(19)
#define CHSR_CONTS_RB           BIT(17)
#define CHSR_ERROR              BIT(15)
#define CHSR_SABORT             BIT(14)
#define CHSR_HABORT             BIT(13)
#define CHSR_STOPS              BIT(12)
#define CHSR_OPERR(x)           (((x) & 0x3) << 10)
#define CHSR_OPERR_MASK         CHSR_OPERR(3)
#define CHSR_OPERR_NOERROR      CHSR_OPERR(0)
#define CHSR_OPERR_FIFOERROR    CHSR_OPERR(1)
#define CHSR_OPERR_LINKERROR    CHSR_OPERR(1)   /* ??? */
#define CHSR_XFERR              BIT(9)
#define CHSR_END                BIT(8)
#define CHSR_DRQ1               BIT(7)
#define CHSR_DRQ0               BIT(6)
#define CHSR_LERR(x)            (((x) & 0x3) << 4)
#define CHSR_LERR_MASK          CHSR_LERR(3)
#define CHSR_LBERR              CHSR_LERR(1)
#define CHSR_LRERR              CHSR_LERR(2)
#define CHSR_LOERR              CHSR_LERR(3)
#define CHSR_MERR(x)            (((x) & 0x3) << 2)
#define CHSR_MERR_MASK          CHSR_MERR(3)
#define CHSR_MBERR              CHSR_MERR(1)
#define CHSR_MRERR              CHSR_MERR(2)
#define CHSR_MOERR              CHSR_MERR(3)
#define CHSR_DERR(x)            (((x) & 0x3) << 0)
#define CHSR_DERR_MASK          CHSR_DERR(3)
#define CHSR_DBERR              CHSR_DERR(1)
#define CHSR_DRERR              CHSR_DERR(2)
#define CHSR_DOERR              CHSR_DERR(3)
#define MITE_FCR(x)             (0x40 + MITE_CHAN(x))   /* fifo count */

/* common bits for the memory/device/link config registers */
#define CR_RL(x)                (((x) & 0x7) << 21)
#define CR_REQS(x)              (((x) & 0x7) << 16)
#define CR_REQS_MASK            CR_REQS(7)
#define CR_ASEQ(x)              (((x) & 0x3) << 10)
#define CR_ASEQDONT             CR_ASEQ(0)
#define CR_ASEQUP               CR_ASEQ(1)
#define CR_ASEQDOWN             CR_ASEQ(2)
#define CR_ASEQ_MASK            CR_ASEQ(3)
#define CR_PSIZE(x)             (((x) & 0x3) << 8)
#define CR_PSIZE8               CR_PSIZE(1)
#define CR_PSIZE16              CR_PSIZE(2)
#define CR_PSIZE32              CR_PSIZE(3)
#define CR_PORT(x)              (((x) & 0x3) << 6)
#define CR_PORTCPU              CR_PORT(0)
#define CR_PORTIO               CR_PORT(1)
#define CR_PORTVXI              CR_PORT(2)
#define CR_PORTMXI              CR_PORT(3)
#define CR_AMDEVICE             BIT(0)

static unsigned int MITE_IODWBSR_1_WSIZE_bits(unsigned int size)
{
        return (ilog2(size) - 1) & 0x1f;
}

static unsigned int mite_retry_limit(unsigned int retry_limit)
{
        unsigned int value = 0;

        if (retry_limit)
                value = 1 + ilog2(retry_limit);
        if (value > 0x7)
                value = 0x7;
        return CR_RL(value);
}

static unsigned int mite_drq_reqs(unsigned int drq_line)
{
        /* This also works on m-series when using channels (drq_line) 4 or 5. */
        return CR_REQS((drq_line & 0x3) | 0x4);
}

static unsigned int mite_fifo_size(struct mite *mite, unsigned int channel)
{
        unsigned int fcr_bits = readl(mite->mmio + MITE_FCR(channel));
        unsigned int empty_count = (fcr_bits >> 16) & 0xff;
        unsigned int full_count = fcr_bits & 0xff;

        return empty_count + full_count;
}

static u32 mite_device_bytes_transferred(struct mite_channel *mite_chan)
{
        struct mite *mite = mite_chan->mite;

        return readl(mite->mmio + MITE_DAR(mite_chan->channel));
}

/**
 * mite_bytes_in_transit() - Returns the number of unread bytes in the fifo.
 * @mite_chan: MITE dma channel.
 */
u32 mite_bytes_in_transit(struct mite_channel *mite_chan)
{
        struct mite *mite = mite_chan->mite;

        return readl(mite->mmio + MITE_FCR(mite_chan->channel)) & 0xff;
}
EXPORT_SYMBOL_GPL(mite_bytes_in_transit);

/* returns lower bound for number of bytes transferred from device to memory */
static u32 mite_bytes_written_to_memory_lb(struct mite_channel *mite_chan)
{
        u32 device_byte_count;

        device_byte_count = mite_device_bytes_transferred(mite_chan);
        return device_byte_count - mite_bytes_in_transit(mite_chan);
}

/* returns upper bound for number of bytes transferred from device to memory */
static u32 mite_bytes_written_to_memory_ub(struct mite_channel *mite_chan)
{
        u32 in_transit_count;

        in_transit_count = mite_bytes_in_transit(mite_chan);
        return mite_device_bytes_transferred(mite_chan) - in_transit_count;
}

/* returns lower bound for number of bytes read from memory to device */
static u32 mite_bytes_read_from_memory_lb(struct mite_channel *mite_chan)
{
        u32 device_byte_count;

        device_byte_count = mite_device_bytes_transferred(mite_chan);
        return device_byte_count + mite_bytes_in_transit(mite_chan);
}

/* returns upper bound for number of bytes read from memory to device */
static u32 mite_bytes_read_from_memory_ub(struct mite_channel *mite_chan)
{
        u32 in_transit_count;

        in_transit_count = mite_bytes_in_transit(mite_chan);
        return mite_device_bytes_transferred(mite_chan) + in_transit_count;
}

static void mite_sync_input_dma(struct mite_channel *mite_chan,
                                struct comedi_subdevice *s)
{
        struct comedi_async *async = s->async;
        int count;
        unsigned int nbytes, old_alloc_count;

        old_alloc_count = async->buf_write_alloc_count;
        /* write alloc as much as we can */
        comedi_buf_write_alloc(s, async->prealloc_bufsz);

        nbytes = mite_bytes_written_to_memory_lb(mite_chan);
        if ((int)(mite_bytes_written_to_memory_ub(mite_chan) -
                  old_alloc_count) > 0) {
                dev_warn(s->device->class_dev,
                         "mite: DMA overwrite of free area\n");
                async->events |= COMEDI_CB_OVERFLOW;
                return;
        }

        count = nbytes - async->buf_write_count;
        /*
         * it's possible count will be negative due to conservative value
         * returned by mite_bytes_written_to_memory_lb
         */
        if (count > 0) {
                comedi_buf_write_free(s, count);
                comedi_inc_scan_progress(s, count);
                async->events |= COMEDI_CB_BLOCK;
        }
}

static void mite_sync_output_dma(struct mite_channel *mite_chan,
                                 struct comedi_subdevice *s)
{
        struct comedi_async *async = s->async;
        struct comedi_cmd *cmd = &async->cmd;
        u32 stop_count = cmd->stop_arg * comedi_bytes_per_scan(s);
        unsigned int old_alloc_count = async->buf_read_alloc_count;
        u32 nbytes_ub, nbytes_lb;
        int count;
        bool finite_regen = (cmd->stop_src == TRIG_NONE && stop_count != 0);

        /* read alloc as much as we can */
        comedi_buf_read_alloc(s, async->prealloc_bufsz);
        nbytes_lb = mite_bytes_read_from_memory_lb(mite_chan);
        if (cmd->stop_src == TRIG_COUNT && (int)(nbytes_lb - stop_count) > 0)
                nbytes_lb = stop_count;
        nbytes_ub = mite_bytes_read_from_memory_ub(mite_chan);
        if (cmd->stop_src == TRIG_COUNT && (int)(nbytes_ub - stop_count) > 0)
                nbytes_ub = stop_count;

        if ((!finite_regen || stop_count > old_alloc_count) &&
            ((int)(nbytes_ub - old_alloc_count) > 0)) {
                dev_warn(s->device->class_dev, "mite: DMA underrun\n");
                async->events |= COMEDI_CB_OVERFLOW;
                return;
        }

        if (finite_regen) {
                /*
                 * This is a special case where we continuously output a finite
                 * buffer.  In this case, we do not free any of the memory,
                 * hence we expect that old_alloc_count will reach a maximum of
                 * stop_count bytes.
                 */
                return;
        }

        count = nbytes_lb - async->buf_read_count;
        if (count > 0) {
                comedi_buf_read_free(s, count);
                async->events |= COMEDI_CB_BLOCK;
        }
}

/**
 * mite_sync_dma() - Sync the MITE dma with the COMEDI async buffer.
 * @mite_chan: MITE dma channel.
 * @s: COMEDI subdevice.
 */
void mite_sync_dma(struct mite_channel *mite_chan, struct comedi_subdevice *s)
{
        if (mite_chan->dir == COMEDI_INPUT)
                mite_sync_input_dma(mite_chan, s);
        else
                mite_sync_output_dma(mite_chan, s);
}
EXPORT_SYMBOL_GPL(mite_sync_dma);

static unsigned int mite_get_status(struct mite_channel *mite_chan)
{
        struct mite *mite = mite_chan->mite;
        unsigned int status;
        unsigned long flags;

        spin_lock_irqsave(&mite->lock, flags);
        status = readl(mite->mmio + MITE_CHSR(mite_chan->channel));
        if (status & CHSR_DONE) {
                mite_chan->done = 1;
                writel(CHOR_CLRDONE,
                       mite->mmio + MITE_CHOR(mite_chan->channel));
        }
        spin_unlock_irqrestore(&mite->lock, flags);
        return status;
}

/**
 * mite_ack_linkc() - Check and ack the LINKC interrupt,
 * @mite_chan: MITE dma channel.
 * @s: COMEDI subdevice.
 * @sync: flag to force a mite_sync_dma().
 *
 * This will also ack the DONE interrupt if active.
 */
void mite_ack_linkc(struct mite_channel *mite_chan,
                    struct comedi_subdevice *s,
                    bool sync)
{
        struct mite *mite = mite_chan->mite;
        unsigned int status;

        status = mite_get_status(mite_chan);
        if (status & CHSR_LINKC) {
                writel(CHOR_CLRLC, mite->mmio + MITE_CHOR(mite_chan->channel));
                sync = true;
        }
        if (sync)
                mite_sync_dma(mite_chan, s);

        if (status & CHSR_XFERR) {
                dev_err(s->device->class_dev,
                        "mite: transfer error %08x\n", status);
                s->async->events |= COMEDI_CB_ERROR;
        }
}
EXPORT_SYMBOL_GPL(mite_ack_linkc);

/**
 * mite_done() - Check is a MITE dma transfer is complete.
 * @mite_chan: MITE dma channel.
 *
 * This will also ack the DONE interrupt if active.
 */
int mite_done(struct mite_channel *mite_chan)
{
        struct mite *mite = mite_chan->mite;
        unsigned long flags;
        int done;

        mite_get_status(mite_chan);
        spin_lock_irqsave(&mite->lock, flags);
        done = mite_chan->done;
        spin_unlock_irqrestore(&mite->lock, flags);
        return done;
}
EXPORT_SYMBOL_GPL(mite_done);

static void mite_dma_reset(struct mite_channel *mite_chan)
{
        writel(CHOR_DMARESET | CHOR_FRESET,
               mite_chan->mite->mmio + MITE_CHOR(mite_chan->channel));
}

/**
 * mite_dma_arm() - Start a MITE dma transfer.
 * @mite_chan: MITE dma channel.
 */
void mite_dma_arm(struct mite_channel *mite_chan)
{
        struct mite *mite = mite_chan->mite;
        unsigned long flags;

        /*
         * memory barrier is intended to insure any twiddling with the buffer
         * is done before writing to the mite to arm dma transfer
         */
        smp_mb();
        spin_lock_irqsave(&mite->lock, flags);
        mite_chan->done = 0;
        /* arm */
        writel(CHOR_START, mite->mmio + MITE_CHOR(mite_chan->channel));
        spin_unlock_irqrestore(&mite->lock, flags);
}
EXPORT_SYMBOL_GPL(mite_dma_arm);

/**
 * mite_dma_disarm() - Stop a MITE dma transfer.
 * @mite_chan: MITE dma channel.
 */
void mite_dma_disarm(struct mite_channel *mite_chan)
{
        struct mite *mite = mite_chan->mite;

        /* disarm */
        writel(CHOR_ABORT, mite->mmio + MITE_CHOR(mite_chan->channel));
}
EXPORT_SYMBOL_GPL(mite_dma_disarm);

/**
 * mite_prep_dma() - Prepare a MITE dma channel for transfers.
 * @mite_chan: MITE dma channel.
 * @num_device_bits: device transfer size (8, 16, or 32-bits).
 * @num_memory_bits: memory transfer size (8, 16, or 32-bits).
 */
void mite_prep_dma(struct mite_channel *mite_chan,
                   unsigned int num_device_bits, unsigned int num_memory_bits)
{
        struct mite *mite = mite_chan->mite;
        unsigned int chcr, mcr, dcr, lkcr;

        mite_dma_reset(mite_chan);

        /* short link chaining mode */
        chcr = CHCR_SET_DMA_IE | CHCR_LINKSHORT | CHCR_SET_DONE_IE |
            CHCR_BURSTEN;
        /*
         * Link Complete Interrupt: interrupt every time a link
         * in MITE_RING is completed. This can generate a lot of
         * extra interrupts, but right now we update the values
         * of buf_int_ptr and buf_int_count at each interrupt. A
         * better method is to poll the MITE before each user
         * "read()" to calculate the number of bytes available.
         */
        chcr |= CHCR_SET_LC_IE;
        if (num_memory_bits == 32 && num_device_bits == 16) {
                /*
                 * Doing a combined 32 and 16 bit byteswap gets the 16 bit
                 * samples into the fifo in the right order. Tested doing 32 bit
                 * memory to 16 bit device transfers to the analog out of a
                 * pxi-6281, which has mite version = 1, type = 4. This also
                 * works for dma reads from the counters on e-series boards.
                 */
                chcr |= CHCR_BYTE_SWAP_DEVICE | CHCR_BYTE_SWAP_MEMORY;
        }
        if (mite_chan->dir == COMEDI_INPUT)
                chcr |= CHCR_DEV_TO_MEM;

        writel(chcr, mite->mmio + MITE_CHCR(mite_chan->channel));

        /* to/from memory */
        mcr = mite_retry_limit(64) | CR_ASEQUP;
        switch (num_memory_bits) {
        case 8:
                mcr |= CR_PSIZE8;
                break;
        case 16:
                mcr |= CR_PSIZE16;
                break;
        case 32:
                mcr |= CR_PSIZE32;
                break;
        default:
                pr_warn("bug! invalid mem bit width for dma transfer\n");
                break;
        }
        writel(mcr, mite->mmio + MITE_MCR(mite_chan->channel));

        /* from/to device */
        dcr = mite_retry_limit(64) | CR_ASEQUP;
        dcr |= CR_PORTIO | CR_AMDEVICE | mite_drq_reqs(mite_chan->channel);
        switch (num_device_bits) {
        case 8:
                dcr |= CR_PSIZE8;
                break;
        case 16:
                dcr |= CR_PSIZE16;
                break;
        case 32:
                dcr |= CR_PSIZE32;
                break;
        default:
                pr_warn("bug! invalid dev bit width for dma transfer\n");
                break;
        }
        writel(dcr, mite->mmio + MITE_DCR(mite_chan->channel));

        /* reset the DAR */
        writel(0, mite->mmio + MITE_DAR(mite_chan->channel));

        /* the link is 32bits */
        lkcr = mite_retry_limit(64) | CR_ASEQUP | CR_PSIZE32;
        writel(lkcr, mite->mmio + MITE_LKCR(mite_chan->channel));

        /* starting address for link chaining */
        writel(mite_chan->ring->dma_addr,
               mite->mmio + MITE_LKAR(mite_chan->channel));
}
EXPORT_SYMBOL_GPL(mite_prep_dma);

/**
 * mite_request_channel_in_range() - Request a MITE dma channel.
 * @mite: MITE device.
 * @ring: MITE dma ring.
 * @min_channel: minimum channel index to use.
 * @max_channel: maximum channel index to use.
 */
struct mite_channel *mite_request_channel_in_range(struct mite *mite,
                                                   struct mite_ring *ring,
                                                   unsigned int min_channel,
                                                   unsigned int max_channel)
{
        struct mite_channel *mite_chan = NULL;
        unsigned long flags;
        int i;

        /*
         * spin lock so mite_release_channel can be called safely
         * from interrupts
         */
        spin_lock_irqsave(&mite->lock, flags);
        for (i = min_channel; i <= max_channel; ++i) {
                mite_chan = &mite->channels[i];
                if (!mite_chan->ring) {
                        mite_chan->ring = ring;
                        break;
                }
                mite_chan = NULL;
        }
        spin_unlock_irqrestore(&mite->lock, flags);
        return mite_chan;
}
EXPORT_SYMBOL_GPL(mite_request_channel_in_range);

/**
 * mite_request_channel() - Request a MITE dma channel.
 * @mite: MITE device.
 * @ring: MITE dma ring.
 */
struct mite_channel *mite_request_channel(struct mite *mite,
                                          struct mite_ring *ring)
{
        return mite_request_channel_in_range(mite, ring, 0,
                                             mite->num_channels - 1);
}
EXPORT_SYMBOL_GPL(mite_request_channel);

/**
 * mite_release_channel() - Release a MITE dma channel.
 * @mite_chan: MITE dma channel.
 */
void mite_release_channel(struct mite_channel *mite_chan)
{
        struct mite *mite = mite_chan->mite;
        unsigned long flags;

        /* spin lock to prevent races with mite_request_channel */
        spin_lock_irqsave(&mite->lock, flags);
        if (mite_chan->ring) {
                mite_dma_disarm(mite_chan);
                mite_dma_reset(mite_chan);
                /*
                 * disable all channel's interrupts (do it after disarm/reset so
                 * MITE_CHCR reg isn't changed while dma is still active!)
                 */
                writel(CHCR_CLR_DMA_IE | CHCR_CLR_LINKP_IE |
                       CHCR_CLR_SAR_IE | CHCR_CLR_DONE_IE |
                       CHCR_CLR_MRDY_IE | CHCR_CLR_DRDY_IE |
                       CHCR_CLR_LC_IE | CHCR_CLR_CONT_RB_IE,
                       mite->mmio + MITE_CHCR(mite_chan->channel));
                mite_chan->ring = NULL;
        }
        spin_unlock_irqrestore(&mite->lock, flags);
}
EXPORT_SYMBOL_GPL(mite_release_channel);

/**
 * mite_init_ring_descriptors() - Initialize a MITE dma ring descriptors.
 * @ring: MITE dma ring.
 * @s: COMEDI subdevice.
 * @nbytes: the size of the dma ring (in bytes).
 *
 * Initializes the ring buffer descriptors to provide correct DMA transfer
 * links to the exact amount of memory required. When the ring buffer is
 * allocated by mite_buf_change(), the default is to initialize the ring
 * to refer to the entire DMA data buffer. A command may call this function
 * later to re-initialize and shorten the amount of memory that will be
 * transferred.
 */
int mite_init_ring_descriptors(struct mite_ring *ring,
                               struct comedi_subdevice *s,
                               unsigned int nbytes)
{
        struct comedi_async *async = s->async;
        struct mite_dma_desc *desc = NULL;
        unsigned int n_full_links = nbytes >> PAGE_SHIFT;
        unsigned int remainder = nbytes % PAGE_SIZE;
        int i;

        dev_dbg(s->device->class_dev,
                "mite: init ring buffer to %u bytes\n", nbytes);

        if ((n_full_links + (remainder > 0 ? 1 : 0)) > ring->n_links) {
                dev_err(s->device->class_dev,
                        "mite: ring buffer too small for requested init\n");
                return -ENOMEM;
        }

        /* We set the descriptors for all full links. */
        for (i = 0; i < n_full_links; ++i) {
                desc = &ring->descs[i];
                desc->count = cpu_to_le32(PAGE_SIZE);
                desc->addr = cpu_to_le32(async->buf_map->page_list[i].dma_addr);
                desc->next = cpu_to_le32(ring->dma_addr +
                                         (i + 1) * sizeof(*desc));
        }

        /* the last link is either a remainder or was a full link. */
        if (remainder > 0) {
                desc = &ring->descs[i];
                /* set the lesser count for the remainder link */
                desc->count = cpu_to_le32(remainder);
                desc->addr = cpu_to_le32(async->buf_map->page_list[i].dma_addr);
        }

        /* Assign the last link->next to point back to the head of the list. */
        desc->next = cpu_to_le32(ring->dma_addr);

        /*
         * barrier is meant to insure that all the writes to the dma descriptors
         * have completed before the dma controller is commanded to read them
         */
        smp_wmb();
        return 0;
}
EXPORT_SYMBOL_GPL(mite_init_ring_descriptors);

static void mite_free_dma_descs(struct mite_ring *ring)
{
        struct mite_dma_desc *descs = ring->descs;

        if (descs) {
                dma_free_coherent(ring->hw_dev,
                                  ring->n_links * sizeof(*descs),
                                  descs, ring->dma_addr);
                ring->descs = NULL;
                ring->dma_addr = 0;
                ring->n_links = 0;
        }
}

/**
 * mite_buf_change() - COMEDI subdevice (*buf_change) for a MITE dma ring.
 * @ring: MITE dma ring.
 * @s: COMEDI subdevice.
 */
int mite_buf_change(struct mite_ring *ring, struct comedi_subdevice *s)
{
        struct comedi_async *async = s->async;
        struct mite_dma_desc *descs;
        unsigned int n_links;

        mite_free_dma_descs(ring);

        if (async->prealloc_bufsz == 0)
                return 0;

        n_links = async->prealloc_bufsz >> PAGE_SHIFT;

        descs = dma_alloc_coherent(ring->hw_dev,
                                   n_links * sizeof(*descs),
                                   &ring->dma_addr, GFP_KERNEL);
        if (!descs) {
                dev_err(s->device->class_dev,
                        "mite: ring buffer allocation failed\n");
                return -ENOMEM;
        }
        ring->descs = descs;
        ring->n_links = n_links;

        return mite_init_ring_descriptors(ring, s, n_links << PAGE_SHIFT);
}
EXPORT_SYMBOL_GPL(mite_buf_change);

/**
 * mite_alloc_ring() - Allocate a MITE dma ring.
 * @mite: MITE device.
 */
struct mite_ring *mite_alloc_ring(struct mite *mite)
{
        struct mite_ring *ring;

        ring = kmalloc(sizeof(*ring), GFP_KERNEL);
        if (!ring)
                return NULL;
        ring->hw_dev = get_device(&mite->pcidev->dev);
        if (!ring->hw_dev) {
                kfree(ring);
                return NULL;
        }
        ring->n_links = 0;
        ring->descs = NULL;
        ring->dma_addr = 0;
        return ring;
}
EXPORT_SYMBOL_GPL(mite_alloc_ring);

/**
 * mite_free_ring() - Free a MITE dma ring and its descriptors.
 * @ring: MITE dma ring.
 */
void mite_free_ring(struct mite_ring *ring)
{
        if (ring) {
                mite_free_dma_descs(ring);
                put_device(ring->hw_dev);
                kfree(ring);
        }
}
EXPORT_SYMBOL_GPL(mite_free_ring);

static int mite_setup(struct comedi_device *dev, struct mite *mite,
                      bool use_win1)
{
        resource_size_t daq_phys_addr;
        unsigned long length;
        int i;
        u32 csigr_bits;
        unsigned int unknown_dma_burst_bits;
        unsigned int wpdep;

        pci_set_master(mite->pcidev);

        mite->mmio = pci_ioremap_bar(mite->pcidev, 0);
        if (!mite->mmio)
                return -ENOMEM;

        dev->mmio = pci_ioremap_bar(mite->pcidev, 1);
        if (!dev->mmio)
                return -ENOMEM;
        daq_phys_addr = pci_resource_start(mite->pcidev, 1);
        length = pci_resource_len(mite->pcidev, 1);

        if (use_win1) {
                writel(0, mite->mmio + MITE_IODWBSR);
                dev_dbg(dev->class_dev,
                        "mite: using I/O Window Base Size register 1\n");
                writel(daq_phys_addr | WENAB |
                       MITE_IODWBSR_1_WSIZE_bits(length),
                       mite->mmio + MITE_IODWBSR_1);
                writel(0, mite->mmio + MITE_IODWCR_1);
        } else {
                writel(daq_phys_addr | WENAB, mite->mmio + MITE_IODWBSR);
        }
        /*
         * Make sure dma bursts work. I got this from running a bus analyzer
         * on a pxi-6281 and a pxi-6713. 6713 powered up with register value
         * of 0x61f and bursts worked. 6281 powered up with register value of
         * 0x1f and bursts didn't work. The NI windows driver reads the
         * register, then does a bitwise-or of 0x600 with it and writes it back.
         *
         * The bits 0x90180700 in MITE_UNKNOWN_DMA_BURST_REG can be
         * written and read back.  The bits 0x1f always read as 1.
         * The rest always read as zero.
         */
        unknown_dma_burst_bits = readl(mite->mmio + MITE_UNKNOWN_DMA_BURST_REG);
        unknown_dma_burst_bits |= UNKNOWN_DMA_BURST_ENABLE_BITS;
        writel(unknown_dma_burst_bits, mite->mmio + MITE_UNKNOWN_DMA_BURST_REG);

        csigr_bits = readl(mite->mmio + MITE_CSIGR);
        mite->num_channels = CSIGR_TO_DMAC(csigr_bits);
        if (mite->num_channels > MAX_MITE_DMA_CHANNELS) {
                dev_warn(dev->class_dev,
                         "mite: bug? chip claims to have %i dma channels. Setting to %i.\n",
                         mite->num_channels, MAX_MITE_DMA_CHANNELS);
                mite->num_channels = MAX_MITE_DMA_CHANNELS;
        }

        /* get the wpdep bits and convert it to the write port fifo depth */
        wpdep = CSIGR_TO_WPDEP(csigr_bits);
        if (wpdep)
                wpdep = BIT(wpdep);

        dev_dbg(dev->class_dev,
                "mite: version = %i, type = %i, mite mode = %i, interface mode = %i\n",
                CSIGR_TO_VER(csigr_bits), CSIGR_TO_TYPE(csigr_bits),
                CSIGR_TO_MMODE(csigr_bits), CSIGR_TO_IMODE(csigr_bits));
        dev_dbg(dev->class_dev,
                "mite: num channels = %i, write post fifo depth = %i, wins = %i, iowins = %i\n",
                CSIGR_TO_DMAC(csigr_bits), wpdep,
                CSIGR_TO_WINS(csigr_bits), CSIGR_TO_IOWINS(csigr_bits));

        for (i = 0; i < mite->num_channels; i++) {
                writel(CHOR_DMARESET, mite->mmio + MITE_CHOR(i));
                /* disable interrupts */
                writel(CHCR_CLR_DMA_IE | CHCR_CLR_LINKP_IE | CHCR_CLR_SAR_IE |
                       CHCR_CLR_DONE_IE | CHCR_CLR_MRDY_IE | CHCR_CLR_DRDY_IE |
                       CHCR_CLR_LC_IE | CHCR_CLR_CONT_RB_IE,
                       mite->mmio + MITE_CHCR(i));
        }
        mite->fifo_size = mite_fifo_size(mite, 0);
        dev_dbg(dev->class_dev, "mite: fifo size is %i.\n", mite->fifo_size);
        return 0;
}

/**
 * mite_attach() - Allocate and initialize a MITE device for a comedi driver.
 * @dev: COMEDI device.
 * @use_win1: flag to use I/O Window 1 instead of I/O Window 0.
 *
 * Called by a COMEDI drivers (*auto_attach).
 *
 * Returns a pointer to the MITE device on success, or NULL if the MITE cannot
 * be allocated or remapped.
 */
struct mite *mite_attach(struct comedi_device *dev, bool use_win1)
{
        struct pci_dev *pcidev = comedi_to_pci_dev(dev);
        struct mite *mite;
        unsigned int i;
        int ret;

        mite = kzalloc(sizeof(*mite), GFP_KERNEL);
        if (!mite)
                return NULL;

        spin_lock_init(&mite->lock);
        mite->pcidev = pcidev;
        for (i = 0; i < MAX_MITE_DMA_CHANNELS; ++i) {
                mite->channels[i].mite = mite;
                mite->channels[i].channel = i;
                mite->channels[i].done = 1;
        }

        ret = mite_setup(dev, mite, use_win1);
        if (ret) {
                if (mite->mmio)
                        iounmap(mite->mmio);
                kfree(mite);
                return NULL;
        }

        return mite;
}
EXPORT_SYMBOL_GPL(mite_attach);

/**
 * mite_detach() - Unmap and free a MITE device for a comedi driver.
 * @mite: MITE device.
 *
 * Called by a COMEDI drivers (*detach).
 */
void mite_detach(struct mite *mite)
{
        if (!mite)
                return;

        if (mite->mmio)
                iounmap(mite->mmio);

        kfree(mite);
}
EXPORT_SYMBOL_GPL(mite_detach);

static int __init mite_module_init(void)
{
        return 0;
}
module_init(mite_module_init);

static void __exit mite_module_exit(void)
{
}
module_exit(mite_module_exit);

MODULE_AUTHOR("Comedi https://www.comedi.org");
MODULE_DESCRIPTION("Comedi helper for NI Mite PCI interface chip");
MODULE_LICENSE("GPL");