Commit f0d1b0b3 authored by David Howells's avatar David Howells Committed by Linus Torvalds

[PATCH] LOG2: Implement a general integer log2 facility in the kernel

This facility provides three entry points:

	ilog2()		Log base 2 of unsigned long
	ilog2_u32()	Log base 2 of u32
	ilog2_u64()	Log base 2 of u64

These facilities can either be used inside functions on dynamic data:

	int do_something(long q)
	{
		...;
		y = ilog2(x)
		...;
	}

Or can be used to statically initialise global variables with constant values:

	unsigned n = ilog2(27);

When performing static initialisation, the compiler will report "error:
initializer element is not constant" if asked to take a log of zero or of
something not reducible to a constant.  They treat negative numbers as
unsigned.

When not dealing with a constant, they fall back to using fls() which permits
them to use arch-specific log calculation instructions - such as BSR on
x86/x86_64 or SCAN on FRV - if available.

[akpm@osdl.org: MMC fix]
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David Howells <dhowells@redhat.com>
Cc: Wojtek Kaniewski <wojtekka@toxygen.net>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent b3d7ae5f
......@@ -25,6 +25,14 @@ config RWSEM_XCHGADD_ALGORITHM
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_FIND_NEXT_BIT
bool
default y
......
......@@ -74,6 +74,14 @@ config RWSEM_GENERIC_SPINLOCK
config RWSEM_XCHGADD_ALGORITHM
bool
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_HWEIGHT
bool
default y
......
......@@ -41,6 +41,14 @@ config RWSEM_GENERIC_SPINLOCK
config RWSEM_XCHGADD_ALGORITHM
bool
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_HWEIGHT
bool
default y
......
......@@ -45,6 +45,14 @@ config GENERIC_TIME
config RWSEM_XCHGADD_ALGORITHM
bool
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_BUST_SPINLOCK
bool
......
......@@ -16,6 +16,14 @@ config RWSEM_GENERIC_SPINLOCK
config RWSEM_XCHGADD_ALGORITHM
bool
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_FIND_NEXT_BIT
bool
default y
......
......@@ -41,6 +41,14 @@ config TIME_LOW_RES
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default y
config ARCH_HAS_ILOG2_U64
bool
default y
mainmenu "Fujitsu FR-V Kernel Configuration"
source "init/Kconfig"
......
......@@ -29,6 +29,14 @@ config RWSEM_XCHGADD_ALGORITHM
bool
default n
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_FIND_NEXT_BIT
bool
default y
......
......@@ -248,6 +248,14 @@ config RWSEM_XCHGADD_ALGORITHM
depends on !M386
default y
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_CALIBRATE_DELAY
bool
default y
......
......@@ -34,6 +34,14 @@ config RWSEM_XCHGADD_ALGORITHM
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_FIND_NEXT_BIT
bool
default y
......
......@@ -214,6 +214,14 @@ config RWSEM_XCHGADD_ALGORITHM
bool
default n
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_FIND_NEXT_BIT
bool
default y
......
......@@ -17,6 +17,14 @@ config RWSEM_GENERIC_SPINLOCK
config RWSEM_XCHGADD_ALGORITHM
bool
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_HWEIGHT
bool
default y
......
......@@ -25,6 +25,14 @@ config RWSEM_XCHGADD_ALGORITHM
bool
default n
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_FIND_NEXT_BIT
bool
default y
......
......@@ -819,6 +819,14 @@ config RWSEM_GENERIC_SPINLOCK
config RWSEM_XCHGADD_ALGORITHM
bool
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_FIND_NEXT_BIT
bool
default y
......
......@@ -25,6 +25,14 @@ config RWSEM_GENERIC_SPINLOCK
config RWSEM_XCHGADD_ALGORITHM
bool
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_FIND_NEXT_BIT
bool
default y
......
......@@ -41,6 +41,14 @@ config RWSEM_XCHGADD_ALGORITHM
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_HWEIGHT
bool
default y
......
......@@ -19,6 +19,14 @@ config RWSEM_XCHGADD_ALGORITHM
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default y
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_HWEIGHT
bool
default y
......
......@@ -22,6 +22,14 @@ config RWSEM_XCHGADD_ALGORITHM
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config GENERIC_HWEIGHT
bool
default y
......
......@@ -59,6 +59,14 @@ config LOCKDEP_SUPPORT
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
source "init/Kconfig"
menu "System type"
......
......@@ -39,6 +39,14 @@ config RWSEM_XCHGADD_ALGORITHM
config GENERIC_ISA_DMA
bool
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
source init/Kconfig
menu "System type"
......
......@@ -166,6 +166,14 @@ config ARCH_MAY_HAVE_PC_FDC
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config SUN_PM
bool
default y
......
......@@ -34,6 +34,14 @@ config ARCH_MAY_HAVE_PC_FDC
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
config AUDIT_ARCH
bool
default y
......
......@@ -38,6 +38,14 @@ config TIME_LOW_RES
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
# Turn off some random 386 crap that can affect device config
config ISA
bool
......
......@@ -101,6 +101,14 @@ config GENERIC_BUG
default y
depends on BUG
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
source "init/Kconfig"
......
......@@ -34,6 +34,14 @@ config GENERIC_HARDIRQS
bool
default y
config ARCH_HAS_ILOG2_U32
bool
default n
config ARCH_HAS_ILOG2_U64
bool
default n
source "init/Kconfig"
menu "Processor type and features"
......
......@@ -124,7 +124,7 @@ static int mthca_query_device(struct ib_device *ibdev,
props->max_map_per_fmr = 255;
else
props->max_map_per_fmr =
(1 << (32 - long_log2(mdev->limits.num_mpts))) - 1;
(1 << (32 - ilog2(mdev->limits.num_mpts))) - 1;
err = 0;
out:
......@@ -816,7 +816,7 @@ static int mthca_resize_cq(struct ib_cq *ibcq, int entries, struct ib_udata *uda
lkey = ucmd.lkey;
}
ret = mthca_RESIZE_CQ(dev, cq->cqn, lkey, long_log2(entries), &status);
ret = mthca_RESIZE_CQ(dev, cq->cqn, lkey, ilog2(entries), &status);
if (status)
ret = -EINVAL;
......
......@@ -636,11 +636,11 @@ int mthca_modify_qp(struct ib_qp *ibqp, struct ib_qp_attr *attr, int attr_mask,
if (mthca_is_memfree(dev)) {
if (qp->rq.max)
qp_context->rq_size_stride = long_log2(qp->rq.max) << 3;
qp_context->rq_size_stride = ilog2(qp->rq.max) << 3;
qp_context->rq_size_stride |= qp->rq.wqe_shift - 4;
if (qp->sq.max)
qp_context->sq_size_stride = long_log2(qp->sq.max) << 3;
qp_context->sq_size_stride = ilog2(qp->sq.max) << 3;
qp_context->sq_size_stride |= qp->sq.wqe_shift - 4;
}
......
......@@ -120,7 +120,7 @@ static void mthca_arbel_init_srq_context(struct mthca_dev *dev,
memset(context, 0, sizeof *context);
logsize = long_log2(srq->max);
logsize = ilog2(srq->max);
context->state_logsize_srqn = cpu_to_be32(logsize << 24 | srq->srqn);
context->lkey = cpu_to_be32(srq->mr.ibmr.lkey);
context->db_index = cpu_to_be32(srq->db_index);
......@@ -213,7 +213,7 @@ int mthca_alloc_srq(struct mthca_dev *dev, struct mthca_pd *pd,
if (!mthca_is_memfree(dev) && (ds > dev->limits.max_desc_sz))
return -EINVAL;
srq->wqe_shift = long_log2(ds);
srq->wqe_shift = ilog2(ds);
srq->srqn = mthca_alloc(&dev->srq_table.alloc);
if (srq->srqn == -1)
......
......@@ -114,7 +114,7 @@ int iser_start_rdma_unaligned_sg(struct iscsi_iser_cmd_task *iser_ctask,
if (cmd_data_len > ISER_KMALLOC_THRESHOLD)
mem = (void *)__get_free_pages(GFP_NOIO,
long_log2(roundup_pow_of_two(cmd_data_len)) - PAGE_SHIFT);
ilog2(roundup_pow_of_two(cmd_data_len)) - PAGE_SHIFT);
else
mem = kmalloc(cmd_data_len, GFP_NOIO);
......@@ -211,7 +211,7 @@ void iser_finalize_rdma_unaligned_sg(struct iscsi_iser_cmd_task *iser_ctask,
if (cmd_data_len > ISER_KMALLOC_THRESHOLD)
free_pages((unsigned long)mem_copy->copy_buf,
long_log2(roundup_pow_of_two(cmd_data_len)) - PAGE_SHIFT);
ilog2(roundup_pow_of_two(cmd_data_len)) - PAGE_SHIFT);
else
kfree(mem_copy->copy_buf);
......
......@@ -220,7 +220,7 @@ static int crypt_iv_benbi_ctr(struct crypt_config *cc, struct dm_target *ti,
const char *opts)
{
unsigned int bs = crypto_blkcipher_blocksize(cc->tfm);
int log = long_log2(bs);
int log = ilog2(bs);
/* we need to calculate how far we must shift the sector count
* to get the cipher block count, we use this shift in _gen */
......
......@@ -387,7 +387,7 @@ static void tifm_sd_prepare_data(struct tifm_sd *card, struct mmc_command *cmd)
writel(TIFM_FIFO_INT_SETALL,
sock->addr + SOCK_DMA_FIFO_INT_ENABLE_CLEAR);
writel(long_log2(cmd->data->blksz) - 2,
writel(ilog2(cmd->data->blksz) - 2,
sock->addr + SOCK_FIFO_PAGE_SIZE);
writel(TIFM_FIFO_ENABLE, sock->addr + SOCK_FIFO_CONTROL);
writel(TIFM_FIFO_INTMASK, sock->addr + SOCK_DMA_FIFO_INT_ENABLE_SET);
......
......@@ -597,8 +597,6 @@ static int ext2_check_descriptors (struct super_block * sb)
return 1;
}
#define log2(n) ffz(~(n))
/*
* Maximal file size. There is a direct, and {,double-,triple-}indirect
* block limit, and also a limit of (2^32 - 1) 512-byte sectors in i_blocks.
......@@ -834,9 +832,9 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
sbi->s_sbh = bh;
sbi->s_mount_state = le16_to_cpu(es->s_state);
sbi->s_addr_per_block_bits =
log2 (EXT2_ADDR_PER_BLOCK(sb));
ilog2 (EXT2_ADDR_PER_BLOCK(sb));
sbi->s_desc_per_block_bits =
log2 (EXT2_DESC_PER_BLOCK(sb));
ilog2 (EXT2_DESC_PER_BLOCK(sb));
if (sb->s_magic != EXT2_SUPER_MAGIC)
goto cantfind_ext2;
......
......@@ -1347,8 +1347,6 @@ static void ext3_orphan_cleanup (struct super_block * sb,
sb->s_flags = s_flags; /* Restore MS_RDONLY status */
}
#define log2(n) ffz(~(n))
/*
* Maximal file size. There is a direct, and {,double-,triple-}indirect
* block limit, and also a limit of (2^32 - 1) 512-byte sectors in i_blocks.
......@@ -1597,8 +1595,8 @@ static int ext3_fill_super (struct super_block *sb, void *data, int silent)
sbi->s_desc_per_block = blocksize / sizeof(struct ext3_group_desc);
sbi->s_sbh = bh;
sbi->s_mount_state = le16_to_cpu(es->s_state);
sbi->s_addr_per_block_bits = log2(EXT3_ADDR_PER_BLOCK(sb));
sbi->s_desc_per_block_bits = log2(EXT3_DESC_PER_BLOCK(sb));
sbi->s_addr_per_block_bits = ilog2(EXT3_ADDR_PER_BLOCK(sb));
sbi->s_desc_per_block_bits = ilog2(EXT3_DESC_PER_BLOCK(sb));
for (i=0; i < 4; i++)
sbi->s_hash_seed[i] = le32_to_cpu(es->s_hash_seed[i]);
sbi->s_def_hash_version = es->s_def_hash_version;
......
......@@ -256,6 +256,50 @@ int __ffs(unsigned long x)
return 31 - bit;
}
/*
* special slimline version of fls() for calculating ilog2_u32()
* - note: no protection against n == 0
*/
#define ARCH_HAS_ILOG2_U32
static inline __attribute__((const))
int __ilog2_u32(u32 n)
{
int bit;
asm("scan %1,gr0,%0" : "=r"(bit) : "r"(n));
return 31 - bit;
}
/*
* special slimline version of fls64() for calculating ilog2_u64()
* - note: no protection against n == 0
*/
#define ARCH_HAS_ILOG2_U64
static inline __attribute__((const))
int __ilog2_u64(u64 n)
{
union {
u64 ll;
struct { u32 h, l; };
} _;
int bit, x, y;
_.ll = n;
asm(" subcc %3,gr0,gr0,icc0 \n"
" ckeq icc0,cc4 \n"
" cscan.p %3,gr0,%0 ,cc4,0 \n"
" setlos #63,%1 \n"
" cscan.p %4,gr0,%0 ,cc4,1 \n"
" setlos #31,%2 \n"
" csub.p %1,%0,%0 ,cc4,0 \n"
" csub %2,%0,%0 ,cc4,1 \n"
: "=&r"(bit), "=r"(x), "=r"(y)
: "0r"(_.h), "r"(_.l)
: "icc0", "cc4"
);
return bit;
}
#include <asm-generic/bitops/sched.h>
#include <asm-generic/bitops/hweight.h>
......
......@@ -13,6 +13,7 @@
#include <linux/types.h>
#include <linux/compiler.h>
#include <linux/bitops.h>
#include <linux/log2.h>
#include <asm/byteorder.h>
#include <asm/bug.h>
......@@ -157,14 +158,6 @@ static inline int printk(const char *s, ...) { return 0; }
unsigned long int_sqrt(unsigned long);
static inline int __attribute_pure__ long_log2(unsigned long x)
{
int r = 0;
for (x >>= 1; x > 0; x >>= 1)
r++;
return r;
}
static inline unsigned long
__attribute_const__ roundup_pow_of_two(unsigned long x)
{
......
/* Integer base 2 logarithm calculation
*
* Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* 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.
*/
#ifndef _LINUX_LOG2_H
#define _LINUX_LOG2_H
#include <linux/types.h>
#include <linux/bitops.h>
/*
* deal with unrepresentable constant logarithms
*/
extern __attribute__((const, noreturn))
int ____ilog2_NaN(void);
/*
* non-constant log of base 2 calculators
* - the arch may override these in asm/bitops.h if they can be implemented
* more efficiently than using fls() and fls64()
* - the arch is not required to handle n==0 if implementing the fallback
*/
#ifndef CONFIG_ARCH_HAS_ILOG2_U32
static inline __attribute__((const))
int __ilog2_u32(u32 n)
{
return fls(n) - 1;
}
#endif
#ifndef CONFIG_ARCH_HAS_ILOG2_U64
static inline __attribute__((const))
int __ilog2_u64(u64 n)
{
return fls64(n) - 1;
}
#endif