/*
 * arch/arm/mach-sa1100/dma.c
 *
 * Support functions for the SA11x0 internal DMA channels.
 *
 * Copyright (C) 2000, 2001 by Nicolas Pitre
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/errno.h>

#include <asm/system.h>
#include <asm/irq.h>
#include <mach/hardware.h>
#include <mach/dma.h>


#undef DEBUG
#ifdef DEBUG
#define DPRINTK( s, arg... )  printk( "dma<%p>: " s, regs , ##arg )
#else
#define DPRINTK( x... )
#endif


typedef struct {
        const char *device_id;          /* device name */
        u_long device;                  /* this channel device, 0  if unused*/
        dma_callback_t callback;        /* to call when DMA completes */
        void *data;                     /* ... with private data ptr */
} sa1100_dma_t;

static sa1100_dma_t dma_chan[SA1100_DMA_CHANNELS];

static DEFINE_SPINLOCK(dma_list_lock);


static irqreturn_t dma_irq_handler(int irq, void *dev_id)
{
        dma_regs_t *dma_regs = dev_id;
        sa1100_dma_t *dma = dma_chan + (((u_int)dma_regs >> 5) & 7);
        int status = dma_regs->RdDCSR;

        if (status & (DCSR_ERROR)) {
                printk(KERN_CRIT "DMA on \"%s\" caused an error\n", dma->device_id);
                dma_regs->ClrDCSR = DCSR_ERROR;
        }

        dma_regs->ClrDCSR = status & (DCSR_DONEA | DCSR_DONEB);
        if (dma->callback) {
                if (status & DCSR_DONEA)
                        dma->callback(dma->data);
                if (status & DCSR_DONEB)
                        dma->callback(dma->data);
        }
        return IRQ_HANDLED;
}


/**
 *      sa1100_request_dma - allocate one of the SA11x0's DMA chanels
 *      @device: The SA11x0 peripheral targeted by this request
 *      @device_id: An ascii name for the claiming device
 *      @callback: Function to be called when the DMA completes
 *      @data: A cookie passed back to the callback function
 *      @dma_regs: Pointer to the location of the allocated channel's identifier
 *
 *      This function will search for a free DMA channel and returns the
 *      address of the hardware registers for that channel as the channel
 *      identifier. This identifier is written to the location pointed by
 *      @dma_regs. The list of possible values for @device are listed into
 *      arch/arm/mach-sa1100/include/mach/dma.h as a dma_device_t enum.
 *
 *      Note that reading from a port and writing to the same port are
 *      actually considered as two different streams requiring separate
 *      DMA registrations.
 *
 *      The @callback function is called from interrupt context when one
 *      of the two possible DMA buffers in flight has terminated. That
 *      function has to be small and efficient while posponing more complex
 *      processing to a lower priority execution context.
 *
 *      If no channels are available, or if the desired @device is already in
 *      use by another DMA channel, then an error code is returned.  This
 *      function must be called before any other DMA calls.
 **/

int sa1100_request_dma (dma_device_t device, const char *device_id,
                        dma_callback_t callback, void *data,
                        dma_regs_t **dma_regs)
{
        sa1100_dma_t *dma = NULL;
        dma_regs_t *regs;
        int i, err;

        *dma_regs = NULL;

        err = 0;
        spin_lock(&dma_list_lock);
        for (i = 0; i < SA1100_DMA_CHANNELS; i++) {
                if (dma_chan[i].device == device) {
                        err = -EBUSY;
                        break;
                } else if (!dma_chan[i].device && !dma) {
                        dma = &dma_chan[i];
                }
        }
        if (!err) {
                if (dma)
                        dma->device = device;
                else
                        err = -ENOSR;
        }
        spin_unlock(&dma_list_lock);
        if (err)
                return err;

        i = dma - dma_chan;
        regs = (dma_regs_t *)&DDAR(i);
        err = request_irq(IRQ_DMA0 + i, dma_irq_handler, IRQF_DISABLED,
                          device_id, regs);
        if (err) {
                printk(KERN_ERR
                       "%s: unable to request IRQ %d for %s\n",
                       __func__, IRQ_DMA0 + i, device_id);
                dma->device = 0;
                return err;
        }

        *dma_regs = regs;
        dma->device_id = device_id;
        dma->callback = callback;
        dma->data = data;

        regs->ClrDCSR =
                (DCSR_DONEA | DCSR_DONEB | DCSR_STRTA | DCSR_STRTB |
                 DCSR_IE | DCSR_ERROR | DCSR_RUN);
        regs->DDAR = device;

        return 0;
}


/**
 *      sa1100_free_dma - free a SA11x0 DMA channel
 *      @regs: identifier for the channel to free
 *
 *      This clears all activities on a given DMA channel and releases it
 *      for future requests.  The @regs identifier is provided by a
 *      successful call to sa1100_request_dma().
 **/

void sa1100_free_dma(dma_regs_t *regs)
{
        int i;

        for (i = 0; i < SA1100_DMA_CHANNELS; i++)
                if (regs == (dma_regs_t *)&DDAR(i))
                        break;
        if (i >= SA1100_DMA_CHANNELS) {
                printk(KERN_ERR "%s: bad DMA identifier\n", __func__);
                return;
        }

        if (!dma_chan[i].device) {
                printk(KERN_ERR "%s: Trying to free free DMA\n", __func__);
                return;
        }

        regs->ClrDCSR =
                (DCSR_DONEA | DCSR_DONEB | DCSR_STRTA | DCSR_STRTB |
                 DCSR_IE | DCSR_ERROR | DCSR_RUN);
        free_irq(IRQ_DMA0 + i, regs);
        dma_chan[i].device = 0;
}


/**
 *      sa1100_start_dma - submit a data buffer for DMA
 *      @regs: identifier for the channel to use
 *      @dma_ptr: buffer physical (or bus) start address
 *      @size: buffer size
 *
 *      This function hands the given data buffer to the hardware for DMA
 *      access. If another buffer is already in flight then this buffer
 *      will be queued so the DMA engine will switch to it automatically
 *      when the previous one is done.  The DMA engine is actually toggling
 *      between two buffers so at most 2 successful calls can be made before
 *      one of them terminates and the callback function is called.
 *
 *      The @regs identifier is provided by a successful call to
 *      sa1100_request_dma().
 *
 *      The @size must not be larger than %MAX_DMA_SIZE.  If a given buffer
 *      is larger than that then it's the caller's responsibility to split
 *      it into smaller chunks and submit them separately. If this is the
 *      case then a @size of %CUT_DMA_SIZE is recommended to avoid ending
 *      up with too small chunks. The callback function can be used to chain
 *      submissions of buffer chunks.
 *
 *      Error return values:
 *      %-EOVERFLOW:    Given buffer size is too big.
 *      %-EBUSY:        Both DMA buffers are already in use.
 *      %-EAGAIN:       Both buffers were busy but one of them just completed
 *                      but the interrupt handler has to execute first.
 *
 *      This function returs 0 on success.
 **/

int sa1100_start_dma(dma_regs_t *regs, dma_addr_t dma_ptr, u_int size)
{
        unsigned long flags;
        u_long status;
        int ret;

        if (dma_ptr & 3)
                printk(KERN_WARNING "DMA: unaligned start address (0x%08lx)\n",
                       (unsigned long)dma_ptr);

        if (size > MAX_DMA_SIZE)
                return -EOVERFLOW;

        local_irq_save(flags);
        status = regs->RdDCSR;

        /* If both DMA buffers are started, there's nothing else we can do. */
        if ((status & (DCSR_STRTA | DCSR_STRTB)) == (DCSR_STRTA | DCSR_STRTB)) {
                DPRINTK("start: st %#x busy\n", status);
                ret = -EBUSY;
                goto out;
        }

        if (((status & DCSR_BIU) && (status & DCSR_STRTB)) ||
            (!(status & DCSR_BIU) && !(status & DCSR_STRTA))) {
                if (status & DCSR_DONEA) {
                        /* give a chance for the interrupt to be processed */
                        ret = -EAGAIN;
                        goto out;
                }
                regs->DBSA = dma_ptr;
                regs->DBTA = size;
                regs->SetDCSR = DCSR_STRTA | DCSR_IE | DCSR_RUN;
                DPRINTK("start a=%#x s=%d on A\n", dma_ptr, size);
        } else {
                if (status & DCSR_DONEB) {
                        /* give a chance for the interrupt to be processed */
                        ret = -EAGAIN;
                        goto out;
                }
                regs->DBSB = dma_ptr;
                regs->DBTB = size;
                regs->SetDCSR = DCSR_STRTB | DCSR_IE | DCSR_RUN;
                DPRINTK("start a=%#x s=%d on B\n", dma_ptr, size);
        }
        ret = 0;

out:
        local_irq_restore(flags);
        return ret;
}


/**
 *      sa1100_get_dma_pos - return current DMA position
 *      @regs: identifier for the channel to use
 *
 *      This function returns the current physical (or bus) address for the
 *      given DMA channel.  If the channel is running i.e. not in a stopped
 *      state then the caller must disable interrupts prior calling this
 *      function and process the returned value before re-enabling them to
 *      prevent races with the completion interrupt handler and the callback
 *      function. The validation of the returned value is the caller's
 *      responsibility as well -- the hardware seems to return out of range
 *      values when the DMA engine completes a buffer.
 *
 *      The @regs identifier is provided by a successful call to
 *      sa1100_request_dma().
 **/

dma_addr_t sa1100_get_dma_pos(dma_regs_t *regs)
{
        int status;

        /*
         * We must determine whether buffer A or B is active.
         * Two possibilities: either we are in the middle of
         * a buffer, or the DMA controller just switched to the
         * next toggle but the interrupt hasn't been serviced yet.
         * The former case is straight forward.  In the later case,
         * we'll do like if DMA is just at the end of the previous
         * toggle since all registers haven't been reset yet.
         * This goes around the edge case and since we're always
         * a little behind anyways it shouldn't make a big difference.
         * If DMA has been stopped prior calling this then the
         * position is exact.
         */
        status = regs->RdDCSR;
        if ((!(status & DCSR_BIU) &&  (status & DCSR_STRTA)) ||
            ( (status & DCSR_BIU) && !(status & DCSR_STRTB)))
                return regs->DBSA;
        else
                return regs->DBSB;
}


/**
 *      sa1100_reset_dma - reset a DMA channel
 *      @regs: identifier for the channel to use
 *
 *      This function resets and reconfigure the given DMA channel. This is
 *      particularly useful after a sleep/wakeup event.
 *
 *      The @regs identifier is provided by a successful call to
 *      sa1100_request_dma().
 **/

void sa1100_reset_dma(dma_regs_t *regs)
{
        int i;

        for (i = 0; i < SA1100_DMA_CHANNELS; i++)
                if (regs == (dma_regs_t *)&DDAR(i))
                        break;
        if (i >= SA1100_DMA_CHANNELS) {
                printk(KERN_ERR "%s: bad DMA identifier\n", __func__);
                return;
        }

        regs->ClrDCSR =
                (DCSR_DONEA | DCSR_DONEB | DCSR_STRTA | DCSR_STRTB |
                 DCSR_IE | DCSR_ERROR | DCSR_RUN);
        regs->DDAR = dma_chan[i].device;
}


EXPORT_SYMBOL(sa1100_request_dma);
EXPORT_SYMBOL(sa1100_free_dma);
EXPORT_SYMBOL(sa1100_start_dma);
EXPORT_SYMBOL(sa1100_get_dma_pos);
EXPORT_SYMBOL(sa1100_reset_dma);