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/*
* Basic general purpose allocator for managing special purpose
* memory, for example, memory that is not managed by the regular
* kmalloc/kfree interface. Uses for this includes on-device special
* memory, uncached memory etc.
*
* It is safe to use the allocator in NMI handlers and other special
* unblockable contexts that could otherwise deadlock on locks. This
* is implemented by using atomic operations and retries on any
* conflicts. The disadvantage is that there may be livelocks in
* extreme cases. For better scalability, one allocator can be used
* for each CPU.
*
* The lockless operation only works if there is enough memory
* available. If new memory is added to the pool a lock has to be
* still taken. So any user relying on locklessness has to ensure
* that sufficient memory is preallocated.
*
* The basic atomic operation of this allocator is cmpxchg on long.
* On architectures that don't have NMI-safe cmpxchg implementation,
* the allocator can NOT be used in NMI handler. So code uses the
* allocator in NMI handler should depend on
* CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
*
* Copyright 2005 (C) Jes Sorensen <jes@trained-monkey.org>
*
* This source code is licensed under the GNU General Public License,
* Version 2. See the file COPYING for more details.
*/

#include <linux/slab.h>
#include <linux/export.h>
#include <linux/bitmap.h>
#include <linux/rculist.h>
#include <linux/interrupt.h>
#include <linux/genalloc.h>
#include <linux/of_address.h>
#include <linux/of_device.h>

static inline size_t chunk_size(const struct gen_pool_chunk *chunk)
{
return chunk->end_addr - chunk->start_addr + 1;
}

static int set_bits_ll(unsigned long *addr, unsigned long mask_to_set)
{
unsigned long val, nval;

nval = *addr;
do {
val = nval;
if (val & mask_to_set)
return -EBUSY;
cpu_relax();
} while ((nval = cmpxchg(addr, val, val | mask_to_set)) != val);

return 0;
}

static int clear_bits_ll(unsigned long *addr, unsigned long mask_to_clear)
{
unsigned long val, nval;

nval = *addr;
do {
val = nval;
if ((val & mask_to_clear) != mask_to_clear)
return -EBUSY;
cpu_relax();
} while ((nval = cmpxchg(addr, val, val & ~mask_to_clear)) != val);

return 0;
}

/*
* bitmap_set_ll - set the specified number of bits at the specified position
* @map: pointer to a bitmap
* @start: a bit position in @map
* @nr: number of bits to set
*
* Set @nr bits start from @start in @map lock-lessly. Several users
* can set/clear the same bitmap simultaneously without lock. If two
* users set the same bit, one user will return remain bits, otherwise
* return 0.
*/
static int bitmap_set_ll(unsigned long *map, int start, int nr)
{
unsigned long *p = map + BIT_WORD(start);
const int size = start + nr;
int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);

while (nr - bits_to_set >= 0) {
if (set_bits_ll(p, mask_to_set))
return nr;
nr -= bits_to_set;
bits_to_set = BITS_PER_LONG;
mask_to_set = ~0UL;
p++;
}
if (nr) {
mask_to_set &= BITMAP_LAST_WORD_MASK(size);
if (set_bits_ll(p, mask_to_set))
return nr;
}

return 0;
}

/*
* bitmap_clear_ll - clear the specified number of bits at the specified position
* @map: pointer to a bitmap
* @start: a bit position in @map
* @nr: number of bits to set
*
* Clear @nr bits start from @start in @map lock-lessly. Several users
* can set/clear the same bitmap simultaneously without lock. If two
* users clear the same bit, one user will return remain bits,
* otherwise return 0.
*/
static int bitmap_clear_ll(unsigned long *map, int start, int nr)
{
unsigned long *p = map + BIT_WORD(start);
const int size = start + nr;
int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);

while (nr - bits_to_clear >= 0) {
if (clear_bits_ll(p, mask_to_clear))
return nr;
nr -= bits_to_clear;
bits_to_clear = BITS_PER_LONG;
mask_to_clear = ~0UL;
p++;
}
if (nr) {
mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
if (clear_bits_ll(p, mask_to_clear))
return nr;
}

return 0;
}

/**
* gen_pool_create - create a new special memory pool
* @min_alloc_order: log base 2 of number of bytes each bitmap bit represents
* @nid: node id of the node the pool structure should be allocated on, or -1
*
* Create a new special memory pool that can be used to manage special purpose
* memory not managed by the regular kmalloc/kfree interface.
*/
struct gen_pool *gen_pool_create(int min_alloc_order, int nid)
{
struct gen_pool *pool;

pool = kmalloc_node(sizeof(struct gen_pool), GFP_KERNEL, nid);
if (pool != NULL) {
spin_lock_init(&pool->lock);
INIT_LIST_HEAD(&pool->chunks);
pool->min_alloc_order = min_alloc_order;
pool->algo = gen_pool_first_fit;
pool->data = NULL;
}
return pool;
}
EXPORT_SYMBOL(gen_pool_create);

/**
* gen_pool_add_virt - add a new chunk of special memory to the pool
* @pool: pool to add new memory chunk to
* @virt: virtual starting address of memory chunk to add to pool
* @phys: physical starting address of memory chunk to add to pool
* @size: size in bytes of the memory chunk to add to pool
* @nid: node id of the node the chunk structure and bitmap should be
* allocated on, or -1
*
* Add a new chunk of special memory to the specified pool.
*
* Returns 0 on success or a -ve errno on failure.
*/
int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phys,
size_t size, int nid)
{
struct gen_pool_chunk *chunk;
int nbits = size >> pool->min_alloc_order;
int nbytes = sizeof(struct gen_pool_chunk) +
BITS_TO_LONGS(nbits) * sizeof(long);

chunk = kzalloc_node(nbytes, GFP_KERNEL, nid);
if (unlikely(chunk == NULL))
return -ENOMEM;

chunk->phys_addr = phys;
chunk->start_addr = virt;
chunk->end_addr = virt + size - 1;
atomic_set(&chunk->avail, size);

spin_lock(&pool->lock);
list_add_rcu(&chunk->next_chunk, &pool->chunks);
spin_unlock(&pool->lock);

return 0;
}
EXPORT_SYMBOL(gen_pool_add_virt);

/**
* gen_pool_virt_to_phys - return the physical address of memory
* @pool: pool to allocate from
* @addr: starting address of memory
*
* Returns the physical address on success, or -1 on error.
*/
phys_addr_t gen_pool_virt_to_phys(struct gen_pool *pool, unsigned long addr)
{
struct gen_pool_chunk *chunk;
phys_addr_t paddr = -1;

rcu_read_lock();
list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
if (addr >= chunk->start_addr && addr <= chunk->end_addr) {
paddr = chunk->phys_addr + (addr - chunk->start_addr);
break;
}
}
rcu_read_unlock();

return paddr;
}
EXPORT_SYMBOL(gen_pool_virt_to_phys);

/**
* gen_pool_destroy - destroy a special memory pool
* @pool: pool to destroy
*
* Destroy the specified special memory pool. Verifies that there are no
* outstanding allocations.
*/
void gen_pool_destroy(struct gen_pool *pool)
{
struct list_head *_chunk, *_next_chunk;
struct gen_pool_chunk *chunk;
int order = pool->min_alloc_order;
int bit, end_bit;

list_for_each_safe(_chunk, _next_chunk, &pool->chunks) {
chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
list_del(&chunk->next_chunk);

end_bit = chunk_size(chunk) >> order;
bit = find_next_bit(chunk->bits, end_bit, 0);
BUG_ON(bit < end_bit);

kfree(chunk);
}
kfree(pool);
return;
}
EXPORT_SYMBOL(gen_pool_destroy);

/**
* gen_pool_alloc - allocate special memory from the pool
* @pool: pool to allocate from
* @size: number of bytes to allocate from the pool
*
* Allocate the requested number of bytes from the specified pool.
* Uses the pool allocation function (with first-fit algorithm by default).
* Can not be used in NMI handler on architectures without
* NMI-safe cmpxchg implementation.
*/
unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
{
struct gen_pool_chunk *chunk;
unsigned long addr = 0;
int order = pool->min_alloc_order;
int nbits, start_bit = 0, end_bit, remain;

#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
BUG_ON(in_nmi());
#endif

if (size == 0)
return 0;

nbits = (size + (1UL << order) - 1) >> order;
rcu_read_lock();
list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
if (size > atomic_read(&chunk->avail))
continue;

end_bit = chunk_size(chunk) >> order;
retry:
start_bit = pool->algo(chunk->bits, end_bit, start_bit, nbits,
pool->data);
if (start_bit >= end_bit)
continue;
remain = bitmap_set_ll(chunk->bits, start_bit, nbits);
if (remain) {
remain = bitmap_clear_ll(chunk->bits, start_bit,
nbits - remain);
BUG_ON(remain);
goto retry;
}

addr = chunk->start_addr + ((unsigned long)start_bit << order);
size = nbits << order;
atomic_sub(size, &chunk->avail);
break;
}
rcu_read_unlock();
return addr;
}
EXPORT_SYMBOL(gen_pool_alloc);

/**
* gen_pool_dma_alloc - allocate special memory from the pool for DMA usage
* @pool: pool to allocate from
* @size: number of bytes to allocate from the pool
* @dma: dma-view physical address return value. Use NULL if unneeded.
*
* Allocate the requested number of bytes from the specified pool.
* Uses the pool allocation function (with first-fit algorithm by default).
* Can not be used in NMI handler on architectures without
* NMI-safe cmpxchg implementation.
*/
void *gen_pool_dma_alloc(struct gen_pool *pool, size_t size, dma_addr_t *dma)
{
unsigned long vaddr;

if (!pool)
return NULL;

vaddr = gen_pool_alloc(pool, size);
if (!vaddr)
return NULL;

if (dma)
*dma = gen_pool_virt_to_phys(pool, vaddr);

return (void *)vaddr;
}
EXPORT_SYMBOL(gen_pool_dma_alloc);

/**
* gen_pool_free - free allocated special memory back to the pool
* @pool: pool to free to
* @addr: starting address of memory to free back to pool
* @size: size in bytes of memory to free
*
* Free previously allocated special memory back to the specified
* pool. Can not be used in NMI handler on architectures without
* NMI-safe cmpxchg implementation.
*/
void gen_pool_free(struct gen_pool *pool, unsigned long addr, size_t size)
{
struct gen_pool_chunk *chunk;
int order = pool->min_alloc_order;
int start_bit, nbits, remain;

#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
BUG_ON(in_nmi());
#endif

nbits = (size + (1UL << order) - 1) >> order;
rcu_read_lock();
list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk) {
if (addr >= chunk->start_addr && addr <= chunk->end_addr) {
BUG_ON(addr + size - 1 > chunk->end_addr);
start_bit = (addr - chunk->start_addr) >> order;
remain = bitmap_clear_ll(chunk->bits, start_bit, nbits);
BUG_ON(remain);
size = nbits << order;
atomic_add(size, &chunk->avail);
rcu_read_unlock();
return;
}
}
rcu_read_unlock();
BUG();
}
EXPORT_SYMBOL(gen_pool_free);

/**
* gen_pool_for_each_chunk - call func for every chunk of generic memory pool
* @pool: the generic memory pool
* @func: func to call
* @data: additional data used by @func
*
* Call @func for every chunk of generic memory pool. The @func is
* called with rcu_read_lock held.
*/
void gen_pool_for_each_chunk(struct gen_pool *pool,
void (*func)(struct gen_pool *pool, struct gen_pool_chunk *chunk, void *data),
void *data)
{
struct gen_pool_chunk *chunk;

rcu_read_lock();
list_for_each_entry_rcu(chunk, &(pool)->chunks, next_chunk)
func(pool, chunk, data);
rcu_read_unlock();
}
EXPORT_SYMBOL(gen_pool_for_each_chunk);

/**
* gen_pool_avail - get available free space of the pool
* @pool: pool to get available free space
*
* Return available free space of the specified pool.
*/
size_t gen_pool_avail(struct gen_pool *pool)
{
struct gen_pool_chunk *chunk;
size_t avail = 0;

rcu_read_lock();
list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
avail += atomic_read(&chunk->avail);
rcu_read_unlock();
return avail;
}
EXPORT_SYMBOL_GPL(gen_pool_avail);

/**
* gen_pool_size - get size in bytes of memory managed by the pool
* @pool: pool to get size
*
* Return size in bytes of memory managed by the pool.
*/
size_t gen_pool_size(struct gen_pool *pool)
{
struct gen_pool_chunk *chunk;
size_t size = 0;

rcu_read_lock();
list_for_each_entry_rcu(chunk, &pool->chunks, next_chunk)
size += chunk_size(chunk);
rcu_read_unlock();
return size;
}
EXPORT_SYMBOL_GPL(gen_pool_size);

/**
* gen_pool_set_algo - set the allocation algorithm
* @pool: pool to change allocation algorithm
* @algo: custom algorithm function
* @data: additional data used by @algo
*
* Call @algo for each memory allocation in the pool.
* If @algo is NULL use gen_pool_first_fit as default
* memory allocation function.
*/
void gen_pool_set_algo(struct gen_pool *pool, genpool_algo_t algo, void *data)
{
rcu_read_lock();

pool->algo = algo;
if (!pool->algo)
pool->algo = gen_pool_first_fit;

pool->data = data;

rcu_read_unlock();
}
EXPORT_SYMBOL(gen_pool_set_algo);

/**
* gen_pool_first_fit - find the first available region
* of memory matching the size requirement (no alignment constraint)
* @map: The address to base the search on
* @size: The bitmap size in bits
* @start: The bitnumber to start searching at
* @nr: The number of zeroed bits we're looking for
* @data: additional data - unused
*/
unsigned long gen_pool_first_fit(unsigned long *map, unsigned long size,
unsigned long start, unsigned int nr, void *data)
{
return bitmap_find_next_zero_area(map, size, start, nr, 0);
}
EXPORT_SYMBOL(gen_pool_first_fit);

/**
* gen_pool_best_fit - find the best fitting region of memory
* macthing the size requirement (no alignment constraint)
* @map: The address to base the search on
* @size: The bitmap size in bits
* @start: The bitnumber to start searching at
* @nr: The number of zeroed bits we're looking for
* @data: additional data - unused
*
* Iterate over the bitmap to find the smallest free region
* which we can allocate the memory.
*/
unsigned long gen_pool_best_fit(unsigned long *map, unsigned long size,
unsigned long start, unsigned int nr, void *data)
{
unsigned long start_bit = size;
unsigned long len = size + 1;
unsigned long index;

index = bitmap_find_next_zero_area(map, size, start, nr, 0);

while (index < size) {
int next_bit = find_next_bit(map, size, index + nr);
if ((next_bit - index) < len) {
len = next_bit - index;
start_bit = index;
if (len == nr)
return start_bit;
}
index = bitmap_find_next_zero_area(map, size,
next_bit + 1, nr, 0);
}

return start_bit;
}
EXPORT_SYMBOL(gen_pool_best_fit);

static void devm_gen_pool_release(struct device *dev, void *res)
{
gen_pool_destroy(*(struct gen_pool **)res);
}

/**
* devm_gen_pool_create - managed gen_pool_create
* @dev: device that provides the gen_pool
* @min_alloc_order: log base 2 of number of bytes each bitmap bit represents
* @nid: node id of the node the pool structure should be allocated on, or -1
*
* Create a new special memory pool that can be used to manage special purpose
* memory not managed by the regular kmalloc/kfree interface. The pool will be
* automatically destroyed by the device management code.
*/
struct gen_pool *devm_gen_pool_create(struct device *dev, int min_alloc_order,
int nid)
{
struct gen_pool **ptr, *pool;

ptr = devres_alloc(devm_gen_pool_release, sizeof(*ptr), GFP_KERNEL);

pool = gen_pool_create(min_alloc_order, nid);
if (pool) {
*ptr = pool;
devres_add(dev, ptr);
} else {
devres_free(ptr);
}

return pool;
}

/**
* dev_get_gen_pool - Obtain the gen_pool (if any) for a device
* @dev: device to retrieve the gen_pool from
*
* Returns the gen_pool for the device if one is present, or NULL.
*/
struct gen_pool *dev_get_gen_pool(struct device *dev)
{
struct gen_pool **p = devres_find(dev, devm_gen_pool_release, NULL,
NULL);

if (!p)
return NULL;
return *p;
}
EXPORT_SYMBOL_GPL(dev_get_gen_pool);

#ifdef CONFIG_OF
/**
* of_get_named_gen_pool - find a pool by phandle property
* @np: device node
* @propname: property name containing phandle(s)
* @index: index into the phandle array
*
* Returns the pool that contains the chunk starting at the physical
* address of the device tree node pointed at by the phandle property,
* or NULL if not found.
*/
struct gen_pool *of_get_named_gen_pool(struct device_node *np,
const char *propname, int index)
{
struct platform_device *pdev;
struct device_node *np_pool;

np_pool = of_parse_phandle(np, propname, index);
if (!np_pool)
return NULL;
pdev = of_find_device_by_node(np_pool);
if (!pdev)
return NULL;
return dev_get_gen_pool(&pdev->dev);
}
EXPORT_SYMBOL_GPL(of_get_named_gen_pool);
#endif /* CONFIG_OF */
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