kernel/linux/arch/arm/mach-pxa/dma.c

   1 /*
   2  *  linux/arch/arm/mach-pxa/dma.c
   3  *
   4  *  PXA DMA registration and IRQ dispatching
   5  *
   6  *  Author:     Nicolas Pitre
   7  *  Created:    Nov 15, 2001
   8  *  Copyright:  MontaVista Software Inc.
   9  *
  10  *  This program is free software; you can redistribute it and/or modify
  11  *  it under the terms of the GNU General Public License version 2 as
  12  *  published by the Free Software Foundation.
  13  */
  14
  15 #include <linux/module.h>
  16 #include <linux/init.h>
  17 #include <linux/kernel.h>
  18 #include <linux/interrupt.h>
  19 #include <linux/errno.h>
  20
  21 #include <asm/system.h>
  22 #include <asm/irq.h>
  23 #include <asm/hardware.h>
  24 #include <asm/dma.h>
  25
  26
  27 static struct dma_channel {
  28         char *name;
  29         void (*irq_handler)(int, void *, struct pt_regs *);
  30         void *data;
  31 } dma_channels[PXA_DMA_CHANNELS];
  32
  33
  34 int pxa_request_dma (char *name, pxa_dma_prio prio,
  35                          void (*irq_handler)(int, void *, struct pt_regs *),
  36                          void *data)
  37 {
  38         unsigned long flags;
  39         int i, found = 0;
  40
  41         /* basic sanity checks */
  42         if (!name || !irq_handler)
  43                 return -EINVAL;
  44
  45         local_irq_save(flags);
  46
  47         /* try grabbing a DMA channel with the requested priority */
  48         for (i = prio; i < prio + PXA_DMA_NBCH(prio); i++) {
  49                 if (!dma_channels[i].name) {
  50                         found = 1;
  51                         break;
  52                 }
  53         }
  54
  55         if (!found) {
  56                 /* requested prio group is full, try hier priorities */
  57                 for (i = prio-1; i >= 0; i--) {
  58                         if (!dma_channels[i].name) {
  59                                 found = 1;
  60                                 break;
  61                         }
  62                 }
  63         }
  64
  65         if (found) {
  66                 DCSR(i) = DCSR_STARTINTR|DCSR_ENDINTR|DCSR_BUSERR;
  67                 dma_channels[i].name = name;
  68                 dma_channels[i].irq_handler = irq_handler;
  69                 dma_channels[i].data = data;
  70         } else {
  71                 printk (KERN_WARNING "No more available DMA channels for %s\n", name);
  72                 i = -ENODEV;
  73         }
  74
  75         local_irq_restore(flags);
  76         return i;
  77 }
  78
  79 void pxa_free_dma (int dma_ch)
  80 {
  81         unsigned long flags;
  82
  83         if (!dma_channels[dma_ch].name) {
  84                 printk (KERN_CRIT
  85                         "%s: trying to free channel %d which is already freed\n",
  86                         __FUNCTION__, dma_ch);
  87                 return;
  88         }
  89
  90         local_irq_save(flags);
  91         DCSR(dma_ch) = DCSR_STARTINTR|DCSR_ENDINTR|DCSR_BUSERR;
  92         dma_channels[dma_ch].name = NULL;
  93         local_irq_restore(flags);
  94 }
  95
  96 static irqreturn_t dma_irq_handler(int irq, void *dev_id, struct pt_regs *regs)
  97 {
  98         int i, dint = DINT;
  99
 100         for (i = 0; i < PXA_DMA_CHANNELS; i++) {
 101                 if (dint & (1 << i)) {
 102                         struct dma_channel *channel = &dma_channels[i];
 103                         if (channel->name && channel->irq_handler) {
 104                                 channel->irq_handler(i, channel->data, regs);
 105                         } else {
 106                                 /*
 107                                  * IRQ for an unregistered DMA channel:
 108                                  * let's clear the interrupts and disable it.
 109                                  */
 110                                 printk (KERN_WARNING "spurious IRQ for DMA channel %d\n", i);
 111                                 DCSR(i) = DCSR_STARTINTR|DCSR_ENDINTR|DCSR_BUSERR;
 112                         }
 113                 }
 114         }
 115         return IRQ_HANDLED;
 116 }
 117
 118 static int __init pxa_dma_init (void)
 119 {
 120         int ret;
 121
 122         ret = request_irq (IRQ_DMA, dma_irq_handler, 0, "DMA", NULL);
 123         if (ret)
 124                 printk (KERN_CRIT "Wow!  Can't register IRQ for DMA\n");
 125         return ret;
 126 }
 127
 128 arch_initcall(pxa_dma_init);
 129
 130 EXPORT_SYMBOL(pxa_request_dma);
 131 EXPORT_SYMBOL(pxa_free_dma);
 132