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
  39 #include <asm/atari_stdma.h>
  40 #include <asm/atariints.h>
  41 #include <asm/atarihw.h>
  42 #include <asm/io.h>
  43 #include <asm/irq.h>
  44
  45 static int stdma_locked;                        /* the semaphore */
  46                                                 /* int func to be called */
  47 static irq_handler_t stdma_isr;
  48 static void *stdma_isr_data;                    /* data passed to isr */
  49 static DECLARE_WAIT_QUEUE_HEAD(stdma_wait);     /* wait queue for ST-DMA */
  50
  51
  52
  53
  54 /***************************** Prototypes *****************************/
  55
  56 static irqreturn_t stdma_int (int irq, void *dummy);
  57
  58 /************************* End of Prototypes **************************/
  59
  60
  61
  62 /*
  63  * Function: void stdma_lock( isrfunc isr, void *data )
  64  *
  65  * Purpose: Tries to get a lock on the ST-DMA chip that is used by more
  66  *   then one device driver. Waits on stdma_wait until lock is free.
  67  *   stdma_lock() may not be called from an interrupt! You have to
  68  *   get the lock in your main routine and release it when your
  69  *   request is finished.
  70  *
  71  * Inputs: A interrupt function that is called until the lock is
  72  *   released.
  73  *
  74  * Returns: nothing
  75  *
  76  */
  77
  78 void stdma_lock(irq_handler_t handler, void *data)
  79 {
  80         unsigned long flags;
  81
  82         local_irq_save(flags);          /* protect lock */
  83
  84         /* Since the DMA is used for file system purposes, we
  85          have to sleep uninterruptible (there may be locked
  86          buffers) */
  87         wait_event(stdma_wait, !stdma_locked);
  88
  89         stdma_locked   = 1;
  90         stdma_isr      = handler;
  91         stdma_isr_data = data;
  92         local_irq_restore(flags);
  93 }
  94
  95
  96 /*
  97  * Function: void stdma_release( void )
  98  *
  99  * Purpose: Releases the lock on the ST-DMA chip.
 100  *
 101  * Inputs: none
 102  *
 103  * Returns: nothing
 104  *
 105  */
 106
 107 void stdma_release(void)
 108 {
 109         unsigned long flags;
 110
 111         local_irq_save(flags);
 112
 113         stdma_locked   = 0;
 114         stdma_isr      = NULL;
 115         stdma_isr_data = NULL;
 116         wake_up(&stdma_wait);
 117
 118         local_irq_restore(flags);
 119 }
 120
 121
 122 /*
 123  * Function: int stdma_others_waiting( void )
 124  *
 125  * Purpose: Check if someone waits for the ST-DMA lock.
 126  *
 127  * Inputs: none
 128  *
 129  * Returns: 0 if no one is waiting, != 0 otherwise
 130  *
 131  */
 132
 133 int stdma_others_waiting(void)
 134 {
 135         return waitqueue_active(&stdma_wait);
 136 }
 137
 138
 139 /*
 140  * Function: int stdma_islocked( void )
 141  *
 142  * Purpose: Check if the ST-DMA is currently locked.
 143  * Note: Returned status is only valid if ints are disabled while calling and
 144  *       as long as they remain disabled.
 145  *       If called with ints enabled, status can change only from locked to
 146  *       unlocked, because ints may not lock the ST-DMA.
 147  *
 148  * Inputs: none
 149  *
 150  * Returns: != 0 if locked, 0 otherwise
 151  *
 152  */
 153
 154 int stdma_islocked(void)
 155 {
 156         return stdma_locked;
 157 }
 158
 159
 160 /*
 161  * Function: void stdma_init( void )
 162  *
 163  * Purpose: Initialize the ST-DMA chip access controlling.
 164  *   It sets up the interrupt and its service routine. The int is registered
 165  *   as slow int, client devices have to live with that (no problem
 166  *   currently).
 167  *
 168  * Inputs: none
 169  *
 170  * Return: nothing
 171  *
 172  */
 173
 174 void __init stdma_init(void)
 175 {
 176         stdma_isr = NULL;
 177         request_irq(IRQ_MFP_FDC, stdma_int, IRQ_TYPE_SLOW | SA_SHIRQ,
 178                     "ST-DMA: floppy/ACSI/IDE/Falcon-SCSI", stdma_int);
 179 }
 180
 181
 182 /*
 183  * Function: void stdma_int()
 184  *
 185  * Purpose: The interrupt routine for the ST-DMA. It calls the isr
 186  *   registered by stdma_lock().
 187  *
 188  */
 189
 190 static irqreturn_t stdma_int(int irq, void *dummy)
 191 {
 192   if (stdma_isr)
 193       (*stdma_isr)(irq, stdma_isr_data);
 194   return IRQ_HANDLED;
 195 }