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linux
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stdma.c
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/* * linux/arch/m68k/atari/stmda.c * * Copyright (C) 1994 Roman Hodek * * * This file is subject to the terms and conditions of the GNU General Public * License. See the file COPYING in the main directory of this archive * for more details. */ /* This file contains some function for controlling the access to the */ /* ST-DMA chip that may be shared between devices. Currently we have: */ /* TT: Floppy and ACSI bus */ /* Falcon: Floppy and SCSI */ /* */ /* The controlling functions set up a wait queue for access to the */ /* ST-DMA chip. Callers to stdma_lock() that cannot granted access are */ /* put onto a queue and waked up later if the owner calls */ /* stdma_release(). Additionally, the caller gives his interrupt */ /* service routine to stdma_lock(). */ /* */ /* On the Falcon, the IDE bus uses just the ACSI/Floppy interrupt, but */ /* not the ST-DMA chip itself. So falhd.c needs not to lock the */ /* chip. The interrupt is routed to falhd.c if IDE is configured, the */ /* model is a Falcon and the interrupt was caused by the HD controller */ /* (can be determined by looking at its status register). */ #include <linux/types.h> #include <linux/kdev_t.h> #include <linux/genhd.h> #include <linux/sched.h> #include <linux/init.h> #include <linux/interrupt.h> #include <linux/wait.h> #include <linux/module.h> #include <asm/atari_stdma.h> #include <asm/atariints.h> #include <asm/atarihw.h> #include <asm/io.h> #include <asm/irq.h> static int stdma_locked; /* the semaphore */ /* int func to be called */ static irq_handler_t stdma_isr; static void *stdma_isr_data; /* data passed to isr */ static DECLARE_WAIT_QUEUE_HEAD(stdma_wait); /* wait queue for ST-DMA */ /***************************** Prototypes *****************************/ static irqreturn_t stdma_int (int irq, void *dummy); /************************* End of Prototypes **************************/ /** * stdma_try_lock - attempt to acquire ST DMA interrupt "lock" * @handler: interrupt handler to use after acquisition * * Returns !0 if lock was acquired; otherwise 0. */ int stdma_try_lock(irq_handler_t handler, void *data) { unsigned long flags; local_irq_save(flags); if (stdma_locked) { local_irq_restore(flags); return 0; } stdma_locked = 1; stdma_isr = handler; stdma_isr_data = data; local_irq_restore(flags); return 1; } EXPORT_SYMBOL(stdma_try_lock); /* * Function: void stdma_lock( isrfunc isr, void *data ) * * Purpose: Tries to get a lock on the ST-DMA chip that is used by more * then one device driver. Waits on stdma_wait until lock is free. * stdma_lock() may not be called from an interrupt! You have to * get the lock in your main routine and release it when your * request is finished. * * Inputs: A interrupt function that is called until the lock is * released. * * Returns: nothing * */ void stdma_lock(irq_handler_t handler, void *data) { /* Since the DMA is used for file system purposes, we have to sleep uninterruptible (there may be locked buffers) */ wait_event(stdma_wait, stdma_try_lock(handler, data)); } EXPORT_SYMBOL(stdma_lock); /* * Function: void stdma_release( void ) * * Purpose: Releases the lock on the ST-DMA chip. * * Inputs: none * * Returns: nothing * */ void stdma_release(void) { unsigned long flags; local_irq_save(flags); stdma_locked = 0; stdma_isr = NULL; stdma_isr_data = NULL; wake_up(&stdma_wait); local_irq_restore(flags); } EXPORT_SYMBOL(stdma_release); /** * stdma_is_locked_by - allow lock holder to check whether it needs to release. * @handler: interrupt handler previously used to acquire lock. * * Returns !0 if locked for the given handler; 0 otherwise. */ int stdma_is_locked_by(irq_handler_t handler) { unsigned long flags; int result; local_irq_save(flags); result = stdma_locked && (stdma_isr == handler); local_irq_restore(flags); return result; } EXPORT_SYMBOL(stdma_is_locked_by); /* * Function: int stdma_islocked( void ) * * Purpose: Check if the ST-DMA is currently locked. * Note: Returned status is only valid if ints are disabled while calling and * as long as they remain disabled. * If called with ints enabled, status can change only from locked to * unlocked, because ints may not lock the ST-DMA. * * Inputs: none * * Returns: != 0 if locked, 0 otherwise * */ int stdma_islocked(void) { return stdma_locked; } EXPORT_SYMBOL(stdma_islocked); /* * Function: void stdma_init( void ) * * Purpose: Initialize the ST-DMA chip access controlling. * It sets up the interrupt and its service routine. The int is registered * as slow int, client devices have to live with that (no problem * currently). * * Inputs: none * * Return: nothing * */ void __init stdma_init(void) { stdma_isr = NULL; if (request_irq(IRQ_MFP_FDC, stdma_int, IRQ_TYPE_SLOW | IRQF_SHARED, "ST-DMA floppy,ACSI,IDE,Falcon-SCSI", stdma_int)) pr_err("Couldn't register ST-DMA interrupt\n"); } /* * Function: void stdma_int() * * Purpose: The interrupt routine for the ST-DMA. It calls the isr * registered by stdma_lock(). * */ static irqreturn_t stdma_int(int irq, void *dummy) { if (stdma_isr) (*stdma_isr)(irq, stdma_isr_data); return IRQ_HANDLED; }
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