diff options
author | Maarten Lankhorst <maarten.lankhorst@linux.intel.com> | 2019-06-26 12:22:54 +0200 |
---|---|---|
committer | Maarten Lankhorst <maarten.lankhorst@linux.intel.com> | 2019-06-26 12:22:54 +0200 |
commit | 355a47ae7ebcf9d605aa809b259d380422e81b8d (patch) | |
tree | f42b3196986c7de89a335b4f57384d249f5663e9 /lib/math/int_sqrt.c | |
parent | b1622cb3be4557fd086831ca7426eafe5f1acc2e (diff) | |
parent | 80d42db02b3a5beb8cffba08207adf5f4c525ee3 (diff) |
Merge remote-tracking branch 'drm/drm-next' into drm-misc-next-fixes
Some fixes have been accidentally pushed to this, so I cannot fost-forward.
Required to pull in the remove-fbcon-notifiers fixes.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Diffstat (limited to 'lib/math/int_sqrt.c')
-rw-r--r-- | lib/math/int_sqrt.c | 70 |
1 files changed, 70 insertions, 0 deletions
diff --git a/lib/math/int_sqrt.c b/lib/math/int_sqrt.c new file mode 100644 index 000000000000..30e0f9770f88 --- /dev/null +++ b/lib/math/int_sqrt.c @@ -0,0 +1,70 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2013 Davidlohr Bueso <davidlohr.bueso@hp.com> + * + * Based on the shift-and-subtract algorithm for computing integer + * square root from Guy L. Steele. + */ + +#include <linux/kernel.h> +#include <linux/export.h> +#include <linux/bitops.h> + +/** + * int_sqrt - computes the integer square root + * @x: integer of which to calculate the sqrt + * + * Computes: floor(sqrt(x)) + */ +unsigned long int_sqrt(unsigned long x) +{ + unsigned long b, m, y = 0; + + if (x <= 1) + return x; + + m = 1UL << (__fls(x) & ~1UL); + while (m != 0) { + b = y + m; + y >>= 1; + + if (x >= b) { + x -= b; + y += m; + } + m >>= 2; + } + + return y; +} +EXPORT_SYMBOL(int_sqrt); + +#if BITS_PER_LONG < 64 +/** + * int_sqrt64 - strongly typed int_sqrt function when minimum 64 bit input + * is expected. + * @x: 64bit integer of which to calculate the sqrt + */ +u32 int_sqrt64(u64 x) +{ + u64 b, m, y = 0; + + if (x <= ULONG_MAX) + return int_sqrt((unsigned long) x); + + m = 1ULL << ((fls64(x) - 1) & ~1ULL); + while (m != 0) { + b = y + m; + y >>= 1; + + if (x >= b) { + x -= b; + y += m; + } + m >>= 2; + } + + return y; +} +EXPORT_SYMBOL(int_sqrt64); +#endif |