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 #include <asm/arch/pxa-regs.h>
  27
  28 static struct dma_channel {
  29         char *name;
  30         void (*irq_handler)(int, void *, struct pt_regs *);
  31         void *data;
  32 } dma_channels[PXA_DMA_CHANNELS];
  33
  34
  35 int pxa_request_dma (char *name, pxa_dma_prio prio,
  36                          void (*irq_handler)(int, void *, struct pt_regs *),
  37                          void *data)
  38 {
  39         unsigned long flags;
  40         int i, found = 0;
  41
  42         /* basic sanity checks */
  43         if (!name || !irq_handler)
  44                 return -EINVAL;
  45
  46         local_irq_save(flags);
  47
  48         /* try grabbing a DMA channel with the requested priority */
  49         for (i = prio; i < prio + PXA_DMA_NBCH(prio); i++) {
  50                 if (!dma_channels[i].name) {
  51                         found = 1;
  52                         break;
  53                 }
  54         }
  55
  56         if (!found) {
  57                 /* requested prio group is full, try hier priorities */
  58                 for (i = prio-1; i >= 0; i--) {
  59                         if (!dma_channels[i].name) {
  60                                 found = 1;
  61                                 break;
  62                         }
  63                 }
  64         }
  65
  66         if (found) {
  67                 DCSR(i) = DCSR_STARTINTR|DCSR_ENDINTR|DCSR_BUSERR;
  68                 dma_channels[i].name = name;
  69                 dma_channels[i].irq_handler = irq_handler;
  70                 dma_channels[i].data = data;
  71         } else {
  72                 printk (KERN_WARNING "No more available DMA channels for %s\n", name);
  73                 i = -ENODEV;
  74         }
  75
  76         local_irq_restore(flags);
  77         return i;
  78 }
  79
  80 void pxa_free_dma (int dma_ch)
  81 {
  82         unsigned long flags;
  83
  84         if (!dma_channels[dma_ch].name) {
  85                 printk (KERN_CRIT
  86                         "%s: trying to free channel %d which is already freed\n",
  87                         __FUNCTION__, dma_ch);
  88                 return;
  89         }
  90
  91         local_irq_save(flags);
  92         DCSR(dma_ch) = DCSR_STARTINTR|DCSR_ENDINTR|DCSR_BUSERR;
  93         dma_channels[dma_ch].name = NULL;
  94         local_irq_restore(flags);
  95 }
  96
  97 static irqreturn_t dma_irq_handler(int irq, void *dev_id, struct pt_regs *regs)
  98 {
  99         int i, dint = DINT;
 100
 101         for (i = 0; i < PXA_DMA_CHANNELS; i++) {
 102                 if (dint & (1 << i)) {
 103                         struct dma_channel *channel = &dma_channels[i];
 104                         if (channel->name && channel->irq_handler) {
 105                                 channel->irq_handler(i, channel->data, regs);
 106                         } else {
 107                                 /*
 108                                  * IRQ for an unregistered DMA channel:
 109                                  * let's clear the interrupts and disable it.
 110                                  */
 111                                 printk (KERN_WARNING "spurious IRQ for DMA channel %d\n", i);
 112                                 DCSR(i) = DCSR_STARTINTR|DCSR_ENDINTR|DCSR_BUSERR;
 113                         }
 114                 }
 115         }
 116         return IRQ_HANDLED;
 117 }
 118
 119 static int __init pxa_dma_init (void)
 120 {
 121         int ret;
 122
 123         ret = request_irq (IRQ_DMA, dma_irq_handler, 0, "DMA", NULL);
 124         if (ret)
 125                 printk (KERN_CRIT "Wow!  Can't register IRQ for DMA\n");
 126         return ret;
 127 }
 128
 129 arch_initcall(pxa_dma_init);
 130
 131 EXPORT_SYMBOL(pxa_request_dma);
 132 EXPORT_SYMBOL(pxa_free_dma);
 133