stdma.c

/*
 *  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/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
 * @data: cookie passed to the interrupt handler function
 *
 * 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, 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;
}