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