arch/m68k/atari/stdma.c

   1 /*
   2  *  linux/arch/m68k/atari/stmda.c
   3  *
   4  *  Copyright (C) 1994 Roman Hodek
   5  *
   6  *
   7  * This file is subject to the terms and conditions of the GNU General Public
   8  * License.  See the file COPYING in the main directory of this archive
   9  * for more details.
  10  */
  11
  12
  13 /* This file contains some function for controlling the access to the  */
  14 /* ST-DMA chip that may be shared between devices. Currently we have:  */
  15 /*   TT:     Floppy and ACSI bus                                       */
  16 /*   Falcon: Floppy and SCSI                                           */
  17 /*                                                                     */
  18 /* The controlling functions set up a wait queue for access to the     */
  19 /* ST-DMA chip. Callers to stdma_lock() that cannot granted access are */
  20 /* put onto a queue and waked up later if the owner calls              */
  21 /* stdma_release(). Additionally, the caller gives his interrupt       */
  22 /* service routine to stdma_lock().                                    */
  23 /*                                                                     */
  24 /* On the Falcon, the IDE bus uses just the ACSI/Floppy interrupt, but */
  25 /* not the ST-DMA chip itself. So falhd.c needs not to lock the        */
  26 /* chip. The interrupt is routed to falhd.c if IDE is configured, the  */
  27 /* model is a Falcon and the interrupt was caused by the HD controller */
  28 /* (can be determined by looking at its status register).              */
  29
  30
  31 #include <linux/types.h>
  32 #include <linux/kdev_t.h>
  33 #include <linux/genhd.h>
  34 #include <linux/sched.h>
  35 #include <linux/init.h>
  36 #include <linux/interrupt.h>
  37 #include <linux/wait.h>
  38 #include <linux/module.h>
  39
  40 #include <asm/atari_stdma.h>
  41 #include <asm/atariints.h>
  42 #include <asm/atarihw.h>
  43 #include <asm/io.h>
  44 #include <asm/irq.h>
  45
  46 static int stdma_locked;                        /* the semaphore */
  47                                                 /* int func to be called */
  48 static irq_handler_t stdma_isr;
  49 static void *stdma_isr_data;                    /* data passed to isr */
  50 static DECLARE_WAIT_QUEUE_HEAD(stdma_wait);     /* wait queue for ST-DMA */
  51
  52
  53
  54
  55 /***************************** Prototypes *****************************/
  56
  57 static irqreturn_t stdma_int (int irq, void *dummy);
  58
  59 /************************* End of Prototypes **************************/
  60
  61
  62
  63 /*
  64  * Function: void stdma_lock( isrfunc isr, void *data )
  65  *
  66  * Purpose: Tries to get a lock on the ST-DMA chip that is used by more
  67  *   then one device driver. Waits on stdma_wait until lock is free.
  68  *   stdma_lock() may not be called from an interrupt! You have to
  69  *   get the lock in your main routine and release it when your
  70  *   request is finished.
  71  *
  72  * Inputs: A interrupt function that is called until the lock is
  73  *   released.
  74  *
  75  * Returns: nothing
  76  *
  77  */
  78
  79 void stdma_lock(irq_handler_t handler, void *data)
  80 {
  81         unsigned long flags;
  82
  83         local_irq_save(flags);          /* protect lock */
  84
  85         /* Since the DMA is used for file system purposes, we
  86          have to sleep uninterruptible (there may be locked
  87          buffers) */
  88         wait_event(stdma_wait, !stdma_locked);
  89
  90         stdma_locked   = 1;
  91         stdma_isr      = handler;
  92         stdma_isr_data = data;
  93         local_irq_restore(flags);
  94 }
  95 EXPORT_SYMBOL(stdma_lock);
  96
  97
  98 /*
  99  * Function: void stdma_release( void )
 100  *
 101  * Purpose: Releases the lock on the ST-DMA chip.
 102  *
 103  * Inputs: none
 104  *
 105  * Returns: nothing
 106  *
 107  */
 108
 109 void stdma_release(void)
 110 {
 111         unsigned long flags;
 112
 113         local_irq_save(flags);
 114
 115         stdma_locked   = 0;
 116         stdma_isr      = NULL;
 117         stdma_isr_data = NULL;
 118         wake_up(&stdma_wait);
 119
 120         local_irq_restore(flags);
 121 }
 122 EXPORT_SYMBOL(stdma_release);
 123
 124
 125 /*
 126  * Function: int stdma_others_waiting( void )
 127  *
 128  * Purpose: Check if someone waits for the ST-DMA lock.
 129  *
 130  * Inputs: none
 131  *
 132  * Returns: 0 if no one is waiting, != 0 otherwise
 133  *
 134  */
 135
 136 int stdma_others_waiting(void)
 137 {
 138         return waitqueue_active(&stdma_wait);
 139 }
 140 EXPORT_SYMBOL(stdma_others_waiting);
 141
 142
 143 /*
 144  * Function: int stdma_islocked( void )
 145  *
 146  * Purpose: Check if the ST-DMA is currently locked.
 147  * Note: Returned status is only valid if ints are disabled while calling and
 148  *       as long as they remain disabled.
 149  *       If called with ints enabled, status can change only from locked to
 150  *       unlocked, because ints may not lock the ST-DMA.
 151  *
 152  * Inputs: none
 153  *
 154  * Returns: != 0 if locked, 0 otherwise
 155  *
 156  */
 157
 158 int stdma_islocked(void)
 159 {
 160         return stdma_locked;
 161 }
 162 EXPORT_SYMBOL(stdma_islocked);
 163
 164
 165 /*
 166  * Function: void stdma_init( void )
 167  *
 168  * Purpose: Initialize the ST-DMA chip access controlling.
 169  *   It sets up the interrupt and its service routine. The int is registered
 170  *   as slow int, client devices have to live with that (no problem
 171  *   currently).
 172  *
 173  * Inputs: none
 174  *
 175  * Return: nothing
 176  *
 177  */
 178
 179 void __init stdma_init(void)
 180 {
 181         stdma_isr = NULL;
 182         request_irq(IRQ_MFP_FDC, stdma_int, IRQ_TYPE_SLOW | IRQF_SHARED,
 183                     "ST-DMA: floppy/ACSI/IDE/Falcon-SCSI", stdma_int);
 184 }
 185
 186
 187 /*
 188  * Function: void stdma_int()
 189  *
 190  * Purpose: The interrupt routine for the ST-DMA. It calls the isr
 191  *   registered by stdma_lock().
 192  *
 193  */
 194
 195 static irqreturn_t stdma_int(int irq, void *dummy)
 196 {
 197   if (stdma_isr)
 198       (*stdma_isr)(irq, stdma_isr_data);
 199   return IRQ_HANDLED;
 200 }