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dma.c

/*
 *  linux/arch/arm/mach-pxa/dma.c
 *
 *  PXA DMA registration and IRQ dispatching
 *
 *  Author: Nicolas Pitre
 *  Created:      Nov 15, 2001
 *  Copyright:    MontaVista Software Inc.
 *
 *  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/init.h>
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/errno.h>

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

#include <asm/arch/pxa-regs.h>

struct dma_channel {
      char *name;
      pxa_dma_prio prio;
      void (*irq_handler)(int, void *);
      void *data;
};

static struct dma_channel *dma_channels;
static int num_dma_channels;

int pxa_request_dma (char *name, pxa_dma_prio prio,
                   void (*irq_handler)(int, void *),
                   void *data)
{
      unsigned long flags;
      int i, found = 0;

      /* basic sanity checks */
      if (!name || !irq_handler)
            return -EINVAL;

      local_irq_save(flags);

      do {
            /* try grabbing a DMA channel with the requested priority */
            for (i = 0; i < num_dma_channels; i++) {
                  if ((dma_channels[i].prio == prio) &&
                      !dma_channels[i].name) {
                        found = 1;
                        break;
                  }
            }
            /* if requested prio group is full, try a hier priority */
      } while (!found && prio--);

      if (found) {
            DCSR(i) = DCSR_STARTINTR|DCSR_ENDINTR|DCSR_BUSERR;
            dma_channels[i].name = name;
            dma_channels[i].irq_handler = irq_handler;
            dma_channels[i].data = data;
      } else {
            printk (KERN_WARNING "No more available DMA channels for %s\n", name);
            i = -ENODEV;
      }

      local_irq_restore(flags);
      return i;
}

void pxa_free_dma (int dma_ch)
{
      unsigned long flags;

      if (!dma_channels[dma_ch].name) {
            printk (KERN_CRIT
                  "%s: trying to free channel %d which is already freed\n",
                  __func__, dma_ch);
            return;
      }

      local_irq_save(flags);
      DCSR(dma_ch) = DCSR_STARTINTR|DCSR_ENDINTR|DCSR_BUSERR;
      dma_channels[dma_ch].name = NULL;
      local_irq_restore(flags);
}

static irqreturn_t dma_irq_handler(int irq, void *dev_id)
{
      int i, dint = DINT;

      for (i = 0; i < num_dma_channels; i++) {
            if (dint & (1 << i)) {
                  struct dma_channel *channel = &dma_channels[i];
                  if (channel->name && channel->irq_handler) {
                        channel->irq_handler(i, channel->data);
                  } else {
                        /*
                         * IRQ for an unregistered DMA channel:
                         * let's clear the interrupts and disable it.
                         */
                        printk (KERN_WARNING "spurious IRQ for DMA channel %d\n", i);
                        DCSR(i) = DCSR_STARTINTR|DCSR_ENDINTR|DCSR_BUSERR;
                  }
            }
      }
      return IRQ_HANDLED;
}

int __init pxa_init_dma(int num_ch)
{
      int i, ret;

      dma_channels = kzalloc(sizeof(struct dma_channel) * num_ch, GFP_KERNEL);
      if (dma_channels == NULL)
            return -ENOMEM;

      ret = request_irq(IRQ_DMA, dma_irq_handler, IRQF_DISABLED, "DMA", NULL);
      if (ret) {
            printk (KERN_CRIT "Wow!  Can't register IRQ for DMA\n");
            kfree(dma_channels);
            return ret;
      }

      /* dma channel priorities on pxa2xx processors:
       * ch 0 - 3,  16 - 19  <--> (0) DMA_PRIO_HIGH
       * ch 4 - 7,  20 - 23  <--> (1) DMA_PRIO_MEDIUM
       * ch 8 - 15, 24 - 31  <--> (2) DMA_PRIO_LOW
       */
      for (i = 0; i < num_ch; i++)
            dma_channels[i].prio = min((i & 0xf) >> 2, DMA_PRIO_LOW);

      num_dma_channels = num_ch;
      return 0;
}

EXPORT_SYMBOL(pxa_request_dma);
EXPORT_SYMBOL(pxa_free_dma);

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