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 * stdma_try_lock - attempt to acquire ST DMA interrupt "lock"
64 * @handler: interrupt handler to use after acquisition
65 *
66 * Returns !0 if lock was acquired; otherwise 0.
67 */
68
69 int stdma_try_lock(irq_handler_t handler, void *data)
70 {
71 unsigned long flags;
72
73 local_irq_save(flags);
74 if (stdma_locked) {
75 local_irq_restore(flags);
76 return 0;
77 }
78
79 stdma_locked = 1;
80 stdma_isr = handler;
81 stdma_isr_data = data;
82 local_irq_restore(flags);
83 return 1;
84 }
85 EXPORT_SYMBOL(stdma_try_lock);
86
87
88 /*
89 * Function: void stdma_lock( isrfunc isr, void *data )
90 *
91 * Purpose: Tries to get a lock on the ST-DMA chip that is used by more
92 * then one device driver. Waits on stdma_wait until lock is free.
93 * stdma_lock() may not be called from an interrupt! You have to
94 * get the lock in your main routine and release it when your
95 * request is finished.
96 *
97 * Inputs: A interrupt function that is called until the lock is
98 * released.
99 *
100 * Returns: nothing
101 *
102 */
103
104 void stdma_lock(irq_handler_t handler, void *data)
105 {
106 /* Since the DMA is used for file system purposes, we
107 have to sleep uninterruptible (there may be locked
108 buffers) */
109 wait_event(stdma_wait, stdma_try_lock(handler, data));
110 }
111 EXPORT_SYMBOL(stdma_lock);
112
113
114 /*
115 * Function: void stdma_release( void )
116 *
117 * Purpose: Releases the lock on the ST-DMA chip.
118 *
119 * Inputs: none
120 *
121 * Returns: nothing
122 *
123 */
124
125 void stdma_release(void)
126 {
127 unsigned long flags;
128
129 local_irq_save(flags);
130
131 stdma_locked = 0;
132 stdma_isr = NULL;
133 stdma_isr_data = NULL;
134 wake_up(&stdma_wait);
135
136 local_irq_restore(flags);
137 }
138 EXPORT_SYMBOL(stdma_release);
139
140
141 /**
142 * stdma_is_locked_by - allow lock holder to check whether it needs to release.
143 * @handler: interrupt handler previously used to acquire lock.
144 *
145 * Returns !0 if locked for the given handler; 0 otherwise.
146 */
147
148 int stdma_is_locked_by(irq_handler_t handler)
149 {
150 unsigned long flags;
151 int result;
152
153 local_irq_save(flags);
154 result = stdma_locked && (stdma_isr == handler);
155 local_irq_restore(flags);
156
157 return result;
158 }
159 EXPORT_SYMBOL(stdma_is_locked_by);
160
161
162 /*
163 * Function: int stdma_islocked( void )
164 *
165 * Purpose: Check if the ST-DMA is currently locked.
166 * Note: Returned status is only valid if ints are disabled while calling and
167 * as long as they remain disabled.
168 * If called with ints enabled, status can change only from locked to
169 * unlocked, because ints may not lock the ST-DMA.
170 *
171 * Inputs: none
172 *
173 * Returns: != 0 if locked, 0 otherwise
174 *
175 */
176
177 int stdma_islocked(void)
178 {
179 return stdma_locked;
180 }
181 EXPORT_SYMBOL(stdma_islocked);
182
183
184 /*
185 * Function: void stdma_init( void )
186 *
187 * Purpose: Initialize the ST-DMA chip access controlling.
188 * It sets up the interrupt and its service routine. The int is registered
189 * as slow int, client devices have to live with that (no problem
190 * currently).
191 *
192 * Inputs: none
193 *
194 * Return: nothing
195 *
196 */
197
198 void __init stdma_init(void)
199 {
200 stdma_isr = NULL;
201 if (request_irq(IRQ_MFP_FDC, stdma_int, IRQF_SHARED,
202 "ST-DMA floppy,ACSI,IDE,Falcon-SCSI", stdma_int))
203 pr_err("Couldn't register ST-DMA interrupt\n");
204 }
205
206
207 /*
208 * Function: void stdma_int()
209 *
210 * Purpose: The interrupt routine for the ST-DMA. It calls the isr
211 * registered by stdma_lock().
212 *
213 */
214
215 static irqreturn_t stdma_int(int irq, void *dummy)
216 {
217 if (stdma_isr)
218 (*stdma_isr)(irq, stdma_isr_data);
219 return IRQ_HANDLED;
220 }