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