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/arch/hardware.h>
  24 #include <asm/dma.h>
  25
  26 #include <asm/arch/pxa-regs.h>
  27
  28 struct dma_channel {
  29         char *name;
  30         pxa_dma_prio prio;
  31         void (*irq_handler)(int, void *);
  32         void *data;
  33 };
  34
  35 static struct dma_channel *dma_channels;
  36 static int num_dma_channels;
  37
  38 int pxa_request_dma (char *name, pxa_dma_prio prio,
  39                          void (*irq_handler)(int, void *),
  40                          void *data)
  41 {
  42         unsigned long flags;
  43         int i, found = 0;
  44
  45         /* basic sanity checks */
  46         if (!name || !irq_handler)
  47                 return -EINVAL;
  48
  49         local_irq_save(flags);
  50
  51         do {
  52                 /* try grabbing a DMA channel with the requested priority */
  53                 for (i = 0; i < num_dma_channels; i++) {
  54                         if ((dma_channels[i].prio == prio) &&
  55                             !dma_channels[i].name) {
  56                                 found = 1;
  57                                 break;
  58                         }
  59                 }
  60                 /* if requested prio group is full, try a hier priority */
  61         } while (!found && prio--);
  62
  63         if (found) {
  64                 DCSR(i) = DCSR_STARTINTR|DCSR_ENDINTR|DCSR_BUSERR;
  65                 dma_channels[i].name = name;
  66                 dma_channels[i].irq_handler = irq_handler;
  67                 dma_channels[i].data = data;
  68         } else {
  69                 printk (KERN_WARNING "No more available DMA channels for %s\n", name);
  70                 i = -ENODEV;
  71         }
  72
  73         local_irq_restore(flags);
  74         return i;
  75 }
  76
  77 void pxa_free_dma (int dma_ch)
  78 {
  79         unsigned long flags;
  80
  81         if (!dma_channels[dma_ch].name) {
  82                 printk (KERN_CRIT
  83                         "%s: trying to free channel %d which is already freed\n",
  84                         __func__, dma_ch);
  85                 return;
  86         }
  87
  88         local_irq_save(flags);
  89         DCSR(dma_ch) = DCSR_STARTINTR|DCSR_ENDINTR|DCSR_BUSERR;
  90         dma_channels[dma_ch].name = NULL;
  91         local_irq_restore(flags);
  92 }
  93
  94 static irqreturn_t dma_irq_handler(int irq, void *dev_id)
  95 {
  96         int i, dint = DINT;
  97
  98         for (i = 0; i < num_dma_channels; i++) {
  99                 if (dint & (1 << i)) {
 100                         struct dma_channel *channel = &dma_channels[i];
 101                         if (channel->name && channel->irq_handler) {
 102                                 channel->irq_handler(i, channel->data);
 103                         } else {
 104                                 /*
 105                                  * IRQ for an unregistered DMA channel:
 106                                  * let's clear the interrupts and disable it.
 107                                  */
 108                                 printk (KERN_WARNING "spurious IRQ for DMA channel %d\n", i);
 109                                 DCSR(i) = DCSR_STARTINTR|DCSR_ENDINTR|DCSR_BUSERR;
 110                         }
 111                 }
 112         }
 113         return IRQ_HANDLED;
 114 }
 115
 116 int __init pxa_init_dma(int num_ch)
 117 {
 118         int i, ret;
 119
 120         dma_channels = kzalloc(sizeof(struct dma_channel) * num_ch, GFP_KERNEL);
 121         if (dma_channels == NULL)
 122                 return -ENOMEM;
 123
 124         ret = request_irq(IRQ_DMA, dma_irq_handler, IRQF_DISABLED, "DMA", NULL);
 125         if (ret) {
 126                 printk (KERN_CRIT "Wow!  Can't register IRQ for DMA\n");
 127                 kfree(dma_channels);
 128                 return ret;
 129         }
 130
 131         /* dma channel priorities on pxa2xx processors:
 132          * ch 0 - 3,  16 - 19  <--> (0) DMA_PRIO_HIGH
 133          * ch 4 - 7,  20 - 23  <--> (1) DMA_PRIO_MEDIUM
 134          * ch 8 - 15, 24 - 31  <--> (2) DMA_PRIO_LOW
 135          */
 136         for (i = 0; i < num_ch; i++)
 137                 dma_channels[i].prio = min((i & 0xf) >> 2, DMA_PRIO_LOW);
 138
 139         num_dma_channels = num_ch;
 140         return 0;
 141 }
 142
 143 EXPORT_SYMBOL(pxa_request_dma);
 144 EXPORT_SYMBOL(pxa_free_dma);