// SPDX-License-Identifier: GPL-2.0+
/*
 * comedi/drivers/ni_labpc_isadma.c
 * ISA DMA support for National Instruments Lab-PC series boards and
 * compatibles.
 *
 * Extracted from ni_labpc.c:
 * Copyright (C) 2001-2003 Frank Mori Hess <fmhess@users.sourceforge.net>
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/comedi/comedidev.h>
#include <linux/comedi/comedi_isadma.h>

#include "ni_labpc.h"
#include "ni_labpc_regs.h"
#include "ni_labpc_isadma.h"

/* size in bytes of dma buffer */
#define LABPC_ISADMA_BUFFER_SIZE        0xff00

/* utility function that suggests a dma transfer size in bytes */
static unsigned int labpc_suggest_transfer_size(struct comedi_device *dev,
                                                struct comedi_subdevice *s,
                                                unsigned int maxbytes)
{
        struct comedi_cmd *cmd = &s->async->cmd;
        unsigned int sample_size = comedi_bytes_per_sample(s);
        unsigned int size;
        unsigned int freq;

        if (cmd->convert_src == TRIG_TIMER)
                freq = 1000000000 / cmd->convert_arg;
        else
                /* return some default value */
                freq = 0xffffffff;

        /* make buffer fill in no more than 1/3 second */
        size = (freq / 3) * sample_size;

        /* set a minimum and maximum size allowed */
        if (size > maxbytes)
                size = maxbytes;
        else if (size < sample_size)
                size = sample_size;

        return size;
}

void labpc_setup_dma(struct comedi_device *dev, struct comedi_subdevice *s)
{
        struct labpc_private *devpriv = dev->private;
        struct comedi_isadma_desc *desc = &devpriv->dma->desc[0];
        struct comedi_cmd *cmd = &s->async->cmd;
        unsigned int sample_size = comedi_bytes_per_sample(s);

        /* set appropriate size of transfer */
        desc->size = labpc_suggest_transfer_size(dev, s, desc->maxsize);
        if (cmd->stop_src == TRIG_COUNT &&
            devpriv->count * sample_size < desc->size)
                desc->size = devpriv->count * sample_size;

        comedi_isadma_program(desc);

        /* set CMD3 bits for caller to enable DMA and interrupt */
        devpriv->cmd3 |= (CMD3_DMAEN | CMD3_DMATCINTEN);
}
EXPORT_SYMBOL_GPL(labpc_setup_dma);

void labpc_drain_dma(struct comedi_device *dev)
{
        struct labpc_private *devpriv = dev->private;
        struct comedi_isadma_desc *desc = &devpriv->dma->desc[0];
        struct comedi_subdevice *s = dev->read_subdev;
        struct comedi_async *async = s->async;
        struct comedi_cmd *cmd = &async->cmd;
        unsigned int max_samples = comedi_bytes_to_samples(s, desc->size);
        unsigned int residue;
        unsigned int nsamples;
        unsigned int leftover;

        /*
         * residue is the number of bytes left to be done on the dma
         * transfer.  It should always be zero at this point unless
         * the stop_src is set to external triggering.
         */
        residue = comedi_isadma_disable(desc->chan);

        /*
         * Figure out how many samples to read for this transfer and
         * how many will be stored for next time.
         */
        nsamples = max_samples - comedi_bytes_to_samples(s, residue);
        if (cmd->stop_src == TRIG_COUNT) {
                if (devpriv->count <= nsamples) {
                        nsamples = devpriv->count;
                        leftover = 0;
                } else {
                        leftover = devpriv->count - nsamples;
                        if (leftover > max_samples)
                                leftover = max_samples;
                }
                devpriv->count -= nsamples;
        } else {
                leftover = max_samples;
        }
        desc->size = comedi_samples_to_bytes(s, leftover);

        comedi_buf_write_samples(s, desc->virt_addr, nsamples);
}
EXPORT_SYMBOL_GPL(labpc_drain_dma);

static void handle_isa_dma(struct comedi_device *dev)
{
        struct labpc_private *devpriv = dev->private;
        struct comedi_isadma_desc *desc = &devpriv->dma->desc[0];

        labpc_drain_dma(dev);

        if (desc->size)
                comedi_isadma_program(desc);

        /* clear dma tc interrupt */
        devpriv->write_byte(dev, 0x1, DMATC_CLEAR_REG);
}

void labpc_handle_dma_status(struct comedi_device *dev)
{
        const struct labpc_boardinfo *board = dev->board_ptr;
        struct labpc_private *devpriv = dev->private;

        /*
         * if a dma terminal count of external stop trigger
         * has occurred
         */
        if (devpriv->stat1 & STAT1_GATA0 ||
            (board->is_labpc1200 && devpriv->stat2 & STAT2_OUTA1))
                handle_isa_dma(dev);
}
EXPORT_SYMBOL_GPL(labpc_handle_dma_status);

void labpc_init_dma_chan(struct comedi_device *dev, unsigned int dma_chan)
{
        struct labpc_private *devpriv = dev->private;

        /* only DMA channels 3 and 1 are valid */
        if (dma_chan != 1 && dma_chan != 3)
                return;

        /* DMA uses 1 buffer */
        devpriv->dma = comedi_isadma_alloc(dev, 1, dma_chan, dma_chan,
                                           LABPC_ISADMA_BUFFER_SIZE,
                                           COMEDI_ISADMA_READ);
}
EXPORT_SYMBOL_GPL(labpc_init_dma_chan);

void labpc_free_dma_chan(struct comedi_device *dev)
{
        struct labpc_private *devpriv = dev->private;

        if (devpriv)
                comedi_isadma_free(devpriv->dma);
}
EXPORT_SYMBOL_GPL(labpc_free_dma_chan);

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

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

MODULE_AUTHOR("Comedi https://www.comedi.org");
MODULE_DESCRIPTION("Comedi NI Lab-PC ISA DMA support");
MODULE_LICENSE("GPL");