arch/arm/plat-pxa/dma.c

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