/*
 * allocator.c -- allocate after high_memory, if available
 *
 * NOTE: this is different from my previous allocator, the one that
 *       assembles pages, which revealed itself both slow and unreliable.
 *
 * Copyright (C) 1998   rubini@linux.it (Alessandro Rubini)
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *

-- Changes --

  Date	      Programmer  Description of changes made
  -------------------------------------------------------------------
  02-Aug-2002 NJC         allocator now steps in 1MB increments, rather
			  than doubling its size each time.
			  Also, allocator_init(u32 *) now returns
			  (in the first arg) the size of the free
			  space.  This is no longer consistent with
			  using the allocator as a module, and some changes
			  may be necessary for that purpose.  This was
			  designed to work with the DT3155 driver, in
			  stand alone mode only!!!
  26-Oct-2009 SS	  Port to 2.6.30 kernel.
 */


#ifndef __KERNEL__
#  define __KERNEL__
#endif
#ifndef MODULE
#  define MODULE
#endif


#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/proc_fs.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/mm.h>	/* PAGE_ALIGN() */
#include <linux/io.h>
#include <linux/slab.h>

#include <asm/page.h>

#include "allocator.h"

/*#define ALL_DEBUG*/
#define ALL_MSG "allocator: "

#undef PDEBUG             /* undef it, just in case */
#ifdef ALL_DEBUG
#  define __static
#  define DUMP_LIST() dump_list()
#  ifdef __KERNEL__
     /* This one if debugging is on, and kernel space */
#    define PDEBUG(fmt, args...) printk(KERN_DEBUG ALL_MSG fmt, ## args)
#  else
     /* This one for user space */
#    define PDEBUG(fmt, args...) fprintf(stderr, fmt, ## args)
#  endif
#else
#  define PDEBUG(fmt, args...) /* not debugging: nothing */
#  define DUMP_LIST()
#  define __static static
#endif

#undef PDEBUGG
#define PDEBUGG(fmt, args...)
/*#define PDEBUGG(fmt, args...) printk( KERN_DEBUG ALL_MSG fmt, ## args)*/


static int allocator_himem = 1; /* 0 = probe, pos. = megs, neg. = disable   */
static int allocator_step = 1;  /* This is the step size in MB              */
static int allocator_probe = 1; /* This is a flag -- 1=probe, 0=don't probe */

static unsigned long allocator_buffer;		/* physical address */
static unsigned long allocator_buffer_size;	/* kilobytes */

/*
 * The allocator keeps a list of DMA areas, so multiple devices
 * can coexist. The list is kept sorted by address
 */

struct allocator_struct {
	unsigned long address;
	unsigned long size;
	struct allocator_struct *next;
};

static struct allocator_struct *allocator_list;

#ifdef ALL_DEBUG
static int dump_list(void)
{
	struct allocator_struct *ptr;

	PDEBUG("Current list:\n");
	for (ptr = allocator_list; ptr; ptr = ptr->next)
		PDEBUG("0x%08lx (size %likB)\n", ptr->address, ptr->size>>10);
	return 0;
}
#endif

/* ========================================================================
 * This function is the actual allocator.
 *
 * If space is available in high memory (as detected at load time), that
 * one is returned. The return value is a physical address (i.e., it can
 * be used straight ahead for DMA, but needs remapping for program use).
 */

unsigned long allocator_allocate_dma(unsigned long kilobytes, gfp_t flags)
{
	struct allocator_struct *ptr = allocator_list, *newptr;
	unsigned long bytes = kilobytes << 10;

	/* check if high memory is available */
	if (!allocator_buffer)
		return 0;

	/* Round it to a multiple of the pagesize */
	bytes = PAGE_ALIGN(bytes);
	PDEBUG("request for %li bytes\n", bytes);

	while (ptr && ptr->next) {
		if (ptr->next->address - (ptr->address + ptr->size) >= bytes)
			break; /* enough space */
		ptr = ptr->next;
	}
	if (!ptr->next) {
		DUMP_LIST();
		PDEBUG("alloc failed\n");
		return 0; /* end of list */
	}
	newptr = kmalloc(sizeof(struct allocator_struct), flags);
	if (!newptr)
		return 0;

	/* ok, now stick it after ptr */
	newptr->address = ptr->address + ptr->size;
	newptr->size = bytes;
	newptr->next = ptr->next;
	ptr->next = newptr;

	DUMP_LIST();
	PDEBUG("returning 0x%08lx\n", newptr->address);
	return newptr->address;
}

int allocator_free_dma(unsigned long address)
{
	struct allocator_struct *ptr = allocator_list, *prev;

	while (ptr && ptr->next) {
		if (ptr->next->address == address)
			break;
		ptr = ptr->next;
	}
	/* the one being freed is ptr->next */
	prev = ptr; ptr = ptr->next;

	if (!ptr) {
		pr_err(ALL_MSG "free_dma but add. not allocated\n");
		return -EINVAL;
	}
	PDEBUGG("freeing: %08lx (%li) next %08lx\n", ptr->address, ptr->size,
		ptr->next->address);
	prev->next = ptr->next;
	kfree(ptr);

	/* dump_list(); */
	return 0;
}

/* ========================================================================
 * Init and cleanup
 *
 * On cleanup everything is released. If the list is not empty, that a
 * problem of our clients
 */
int allocator_init(u32 *allocator_max)
{
	/* check how much free memory is there */
	void *remapped;
	unsigned long max;
	unsigned long trial_size = allocator_himem<<20;
	unsigned long last_trial = 0;
	unsigned long step = allocator_step<<20;
	unsigned long i = 0;
	struct allocator_struct *head, *tail;
	char test_string[] = "0123456789abcde"; /* 16 bytes */

	PDEBUGG("himem = %i\n", allocator_himem);
	if (allocator_himem < 0) /* don't even try */
		return -EINVAL;

	if (!trial_size)
		trial_size = 1<<20; /* not specified: try one meg */

	while (1) {
		remapped = ioremap(__pa(high_memory), trial_size);
		if (!remapped) {
			PDEBUGG("%li megs failed!\n", trial_size>>20);
			break;
		}
		PDEBUGG("Trying %li megs (at %p, %p)\n", trial_size>>20,
			(void *)__pa(high_memory), remapped);
		for (i = last_trial; i < trial_size; i += 16) {
			strcpy((char *)(remapped)+i, test_string);
			if (strcmp((char *)(remapped)+i, test_string))
				break;
			}
		iounmap((void *)remapped);
		schedule();
		last_trial = trial_size;
		if (i == trial_size)
			trial_size += step; /* increment, if all went well */
		else {
			PDEBUGG("%li megs copy test failed!\n", trial_size>>20);
			break;
		}
		if (!allocator_probe)
			break;
	}
	PDEBUG("%li megs (%li k, %li b)\n", i>>20, i>>10, i);
	allocator_buffer_size = i>>10; /* kilobytes */
	allocator_buffer = __pa(high_memory);
	if (!allocator_buffer_size) {
		printk(KERN_WARNING ALL_MSG "no free high memory to use\n");
		return -ENOMEM;
	}

	/*
	* to simplify things, always have two cells in the list:
	* the first and the last. This avoids some conditionals and
	* extra code when allocating and deallocating: we only play
	* in the middle of the list
	*/
	head = kmalloc(sizeof(struct allocator_struct), GFP_KERNEL);
	if (!head)
		return -ENOMEM;
	tail = kmalloc(sizeof(struct allocator_struct), GFP_KERNEL);
	if (!tail) {
		kfree(head);
		return -ENOMEM;
	}

	max = allocator_buffer_size<<10;

	head->size = tail->size = 0;
	head->address = allocator_buffer;
	tail->address = allocator_buffer + max;
	head->next = tail;
	tail->next = NULL;
	allocator_list = head;

	/* Back to the user code, in KB */
	*allocator_max = allocator_buffer_size;

	return 0; /* ok, ready */
}

void allocator_cleanup(void)
{
	struct allocator_struct *ptr, *next;

	for (ptr = allocator_list; ptr; ptr = next) {
		next = ptr->next;
		PDEBUG("freeing list: 0x%08lx\n", ptr->address);
		kfree(ptr);
	}

	allocator_buffer      = 0;
	allocator_buffer_size = 0;
	allocator_list = NULL;
}