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#!/usr/bin/perl
# -----------------------------------------------------------------------
#
# Copyright 2007-2008 rPath, Inc. - All Rights Reserved
#
# This file is part of the Linux kernel, and is made available under
# the terms of the GNU General Public License version 2 or (at your
# option) any later version; incorporated herein by reference.
#
# -----------------------------------------------------------------------
#

#
# Usage: timeconst.pl HZ > timeconst.h
#

# Precomputed values for systems without Math::BigInt
# Generated by:
# timeconst.pl --can 24 32 48 64 100 122 128 200 250 256 300 512 1000 1024 1200
%canned_values = (
24 => [
'0xa6aaaaab','0x2aaaaaa',26,
125,3,
'0xc49ba5e4','0x1fbe76c8b4',37,
3,125,
'0xa2c2aaab','0xaaaa',16,
125000,3,
'0xc9539b89','0x7fffbce4217d',47,
3,125000,
], 32 => [
'0xfa000000','0x6000000',27,
125,4,
'0x83126e98','0xfdf3b645a',36,
4,125,
'0xf4240000','0x0',17,
31250,1,
'0x8637bd06','0x3fff79c842fa',46,
1,31250,
], 48 => [
'0xa6aaaaab','0x6aaaaaa',27,
125,6,
'0xc49ba5e4','0xfdf3b645a',36,
6,125,
'0xa2c2aaab','0x15555',17,
62500,3,
'0xc9539b89','0x3fffbce4217d',46,
3,62500,
], 64 => [
'0xfa000000','0xe000000',28,
125,8,
'0x83126e98','0x7ef9db22d',35,
8,125,
'0xf4240000','0x0',18,
15625,1,
'0x8637bd06','0x1fff79c842fa',45,
1,15625,
], 100 => [
'0xa0000000','0x0',28,
10,1,
'0xcccccccd','0x733333333',35,
1,10,
'0x9c400000','0x0',18,
10000,1,
'0xd1b71759','0x1fff2e48e8a7',45,
1,10000,
], 122 => [
'0x8325c53f','0xfbcda3a',28,
500,61,
'0xf9db22d1','0x7fbe76c8b',35,
61,500,
'0x8012e2a0','0x3ef36',18,
500000,61,
'0xffda4053','0x1ffffbce4217',45,
61,500000,
], 128 => [
'0xfa000000','0x1e000000',29,
125,16,
'0x83126e98','0x3f7ced916',34,
16,125,
'0xf4240000','0x40000',19,
15625,2,
'0x8637bd06','0xfffbce4217d',44,
2,15625,
], 200 => [
'0xa0000000','0x0',29,
5,1,
'0xcccccccd','0x333333333',34,
1,5,
'0x9c400000','0x0',19,
5000,1,
'0xd1b71759','0xfff2e48e8a7',44,
1,5000,
], 250 => [
'0x80000000','0x0',29,
4,1,
'0x80000000','0x180000000',33,
1,4,
'0xfa000000','0x0',20,
4000,1,
'0x83126e98','0x7ff7ced9168',43,
1,4000,
], 256 => [
'0xfa000000','0x3e000000',30,
125,32,
'0x83126e98','0x1fbe76c8b',33,
32,125,
'0xf4240000','0xc0000',20,
15625,4,
'0x8637bd06','0x7ffde7210be',43,
4,15625,
], 300 => [
'0xd5555556','0x2aaaaaaa',30,
10,3,
'0x9999999a','0x1cccccccc',33,
3,10,
'0xd0555556','0xaaaaa',20,
10000,3,
'0x9d495183','0x7ffcb923a29',43,
3,10000,
], 512 => [
'0xfa000000','0x7e000000',31,
125,64,
'0x83126e98','0xfdf3b645',32,
64,125,
'0xf4240000','0x1c0000',21,
15625,8,
'0x8637bd06','0x3ffef39085f',42,
8,15625,
], 1000 => [
'0x80000000','0x0',31,
1,1,
'0x80000000','0x0',31,
1,1,
'0xfa000000','0x0',22,
1000,1,
'0x83126e98','0x1ff7ced9168',41,
1,1000,
], 1024 => [
'0xfa000000','0xfe000000',32,
125,128,
'0x83126e98','0x7ef9db22',31,
128,125,
'0xf4240000','0x3c0000',22,
15625,16,
'0x8637bd06','0x1fff79c842f',41,
16,15625,
], 1200 => [
'0xd5555556','0xd5555555',32,
5,6,
'0x9999999a','0x66666666',31,
6,5,
'0xd0555556','0x2aaaaa',22,
2500,3,
'0x9d495183','0x1ffcb923a29',41,
3,2500,
]
);

$has_bigint = eval 'use Math::BigInt qw(bgcd); 1;';

sub bint($)
{
my($x) = @_;
return Math::BigInt->new($x);
}

#
# Constants for division by reciprocal multiplication.
# (bits, numerator, denominator)
#
sub fmul($$$)
{
my ($b,$n,$d) = @_;

$n = bint($n);
$d = bint($d);

return scalar (($n << $b)+$d-bint(1))/$d;
}

sub fadj($$$)
{
my($b,$n,$d) = @_;

$n = bint($n);
$d = bint($d);

$d = $d/bgcd($n, $d);
return scalar (($d-bint(1)) << $b)/$d;
}

sub fmuls($$$) {
my($b,$n,$d) = @_;
my($s,$m);
my($thres) = bint(1) << ($b-1);

$n = bint($n);
$d = bint($d);

for ($s = 0; 1; $s++) {
$m = fmul($s,$n,$d);
return $s if ($m >= $thres);
}
return 0;
}

# Generate a hex value if the result fits in 64 bits;
# otherwise skip.
sub bignum_hex($) {
my($x) = @_;
my $s = $x->as_hex();

return (length($s) > 18) ? undef : $s;
}

# Provides mul, adj, and shr factors for a specific
# (bit, time, hz) combination
sub muladj($$$) {
my($b, $t, $hz) = @_;
my $s = fmuls($b, $t, $hz);
my $m = fmul($s, $t, $hz);
my $a = fadj($s, $t, $hz);
return (bignum_hex($m), bignum_hex($a), $s);
}

# Provides numerator, denominator values
sub numden($$) {
my($n, $d) = @_;
my $g = bgcd($n, $d);
return ($n/$g, $d/$g);
}

# All values for a specific (time, hz) combo
sub conversions($$) {
my ($t, $hz) = @_;
my @val = ();

# HZ_TO_xx
push(@val, muladj(32, $t, $hz));
push(@val, numden($t, $hz));

# xx_TO_HZ
push(@val, muladj(32, $hz, $t));
push(@val, numden($hz, $t));

return @val;
}

sub compute_values($) {
my($hz) = @_;
my @val = ();
my $s, $m, $a, $g;

if (!$has_bigint) {
die "$0: HZ == $hz not canned and ".
"Math::BigInt not available\n";
}

# MSEC conversions
push(@val, conversions(1000, $hz));

# USEC conversions
push(@val, conversions(1000000, $hz));

return @val;
}

sub outputval($$)
{
my($name, $val) = @_;
my $csuf;

if (defined($val)) {
if ($name !~ /SHR/) {
$val = "U64_C($val)";
}
printf "#define %-23s %s\n", $name.$csuf, $val.$csuf;
}
}

sub output($@)
{
my($hz, @val) = @_;
my $pfx, $bit, $suf, $s, $m, $a;

print "/* Automatically generated by kernel/timeconst.pl */\n";
print "/* Conversion constants for HZ == $hz */\n";
print "\n";
print "#ifndef KERNEL_TIMECONST_H\n";
print "#define KERNEL_TIMECONST_H\n";
print "\n";

print "#include <linux/param.h>\n";
print "#include <linux/types.h>\n";

print "\n";
print "#if HZ != $hz\n";
print "#error \"kernel/timeconst.h has the wrong HZ value!\"\n";
print "#endif\n";
print "\n";

foreach $pfx ('HZ_TO_MSEC','MSEC_TO_HZ',
'HZ_TO_USEC','USEC_TO_HZ') {
foreach $bit (32) {
foreach $suf ('MUL', 'ADJ', 'SHR') {
outputval("${pfx}_$suf$bit", shift(@val));
}
}
foreach $suf ('NUM', 'DEN') {
outputval("${pfx}_$suf", shift(@val));
}
}

print "\n";
print "#endif /* KERNEL_TIMECONST_H */\n";
}

# Pretty-print Perl values
sub perlvals(@) {
my $v;
my @l = ();

foreach $v (@_) {
if (!defined($v)) {
push(@l, 'undef');
} elsif ($v =~ /^0x/) {
push(@l, "\'".$v."\'");
} else {
push(@l, $v.'');
}
}
return join(',', @l);
}

($hz) = @ARGV;

# Use this to generate the %canned_values structure
if ($hz eq '--can') {
shift(@ARGV);
@hzlist = sort {$a <=> $b} (@ARGV);

print "# Precomputed values for systems without Math::BigInt\n";
print "# Generated by:\n";
print "# timeconst.pl --can ", join(' ', @hzlist), "\n";
print "\%canned_values = (\n";
my $pf = "\t";
foreach $hz (@hzlist) {
my @values = compute_values($hz);
print "$pf$hz => [\n";
while (scalar(@values)) {
my $bit;
foreach $bit (32) {
my $m = shift(@values);
my $a = shift(@values);
my $s = shift(@values);
print "\t\t", perlvals($m,$a,$s), ",\n";
}
my $n = shift(@values);
my $d = shift(@values);
print "\t\t", perlvals($n,$d), ",\n";
}
print "\t]";
$pf = ', ';
}
print "\n);\n";
} else {
$hz += 0; # Force to number
if ($hz < 1) {
die "Usage: $0 HZ\n";
}

@val = @{$canned_values{$hz}};
if (!defined(@val)) {
@val = compute_values($hz);
}
output($hz, @val);
}
exit 0;
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