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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2026-08-23 13:28:57 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2026-08-23 13:28:57 -0700 |
| commit | 4352b8aee98005853aa63f57d6377282de17a33f (patch) | |
| tree | 27614d7a9ef05c32d089004e104364ce42324837 /lib/math/div64.c | |
| download | linux-stable-4352b8aee98005853aa63f57d6377282de17a33f.tar.gz linux-stable-4352b8aee98005853aa63f57d6377282de17a33f.zip | |
Merge tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linuxgrafted
Pull I3C updates from Alexandre Belloni:
"A new driver this cycle, for the AMD AXI I3C controller.
There are also new features such as IBI wakeup support, SETAASA device
discovery and ACPI support for the the DAA methods, meaning we can now
communicate with the SPD devices on DDR5 modules.
New driver:
- AMD AXI I3C master controller
Subsystem:
- I3C Common Command Code (CCC) handling improvements, especially
around GET CCCs
- SETAASA device discovery support
- ACPI support for all existing DAA methods like SETDASA, SETNEWDA as
well as I2C devices on I3C bus
- IBI-based wakeup support
Drivers:
- dw: SETAASA support
- mipi-i3c-hci: advertise IBI wakeup capability, AMD_PT I3C
controller support, PIO queue management support for HCI v1.2
- renesas: improve suspend to RAM support, add runtime PM support"
* tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux: (70 commits)
i3c: dw: reduce do_daa time if there's no client
i3c: mipi-i3c-hci: Add support for AMD_PT I3C controller
i3c: mipi-i3c-hci: Add PIO queue management support for HCI v1.2
i3c: mipi-i3c-hci: Fix missing STAT_IBI_STATUS_THLD in PIO mode
i3c: dw: rename "pclk" to "apb" to match dt-binding
i3c: dw: make struct dw_i3c_cmd smaller
i3c: dw: use COMMAND_PORT_TRANSFER_ARG instead of hardcoding
i3c: renesas: Don't register devices when ENTDAA times out
i3c: master: dw-i3c-master: fix OD timing for first broadcast
i3c: mipi-i3c-hci: Advertise IBI wakeup capability
i3c: mipi-i3c-hci: Factor out i3c_hci_sysdev()
i3c: mipi-i3c-hci-pci: Propagate I3C wakeup requirements to PCI
i3c: master: Reject IBI requests from non-IBI-capable devices
i3c: master: Add helper to query bus wakeup requirements
i3c: master: Report wakeup events for IBIs
i3c: master: Support IBI-based wakeup capability
i3c: master: Fix potential UAF in i3c_device_match()
i3c: master: Fix potential UAF in i3c_device_uevent()
i3c: Make dev->desc locking assumptions explicit
i3c: master: Fix use-after-free of master->this
...
Diffstat (limited to 'lib/math/div64.c')
| -rw-r--r-- | lib/math/div64.c | 333 |
1 files changed, 333 insertions, 0 deletions
diff --git a/lib/math/div64.c b/lib/math/div64.c new file mode 100644 index 000000000..d1e92ea24 --- /dev/null +++ b/lib/math/div64.c @@ -0,0 +1,333 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com> + * + * Based on former do_div() implementation from asm-parisc/div64.h: + * Copyright (C) 1999 Hewlett-Packard Co + * Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com> + * + * + * Generic C version of 64bit/32bit division and modulo, with + * 64bit result and 32bit remainder. + * + * The fast case for (n>>32 == 0) is handled inline by do_div(). + * + * Code generated for this function might be very inefficient + * for some CPUs. __div64_32() can be overridden by linking arch-specific + * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S + * or by defining a preprocessor macro in arch/include/asm/div64.h. + */ + +#include <linux/bitops.h> +#include <linux/export.h> +#include <linux/math.h> +#include <linux/math64.h> +#include <linux/minmax.h> +#include <linux/log2.h> + +/* Not needed on 64bit architectures */ +#if BITS_PER_LONG == 32 + +#ifndef __div64_32 +uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base) +{ + uint64_t rem = *n; + uint64_t b = base; + uint64_t res, d = 1; + uint32_t high = rem >> 32; + + /* Reduce the thing a bit first */ + res = 0; + if (high >= base) { + high /= base; + res = (uint64_t) high << 32; + rem -= (uint64_t) (high*base) << 32; + } + + while ((int64_t)b > 0 && b < rem) { + b = b+b; + d = d+d; + } + + do { + if (rem >= b) { + rem -= b; + res += d; + } + b >>= 1; + d >>= 1; + } while (d); + + *n = res; + return rem; +} +EXPORT_SYMBOL(__div64_32); +#endif + +#ifndef div_s64_rem +s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder) +{ + u64 quotient; + + if (dividend < 0) { + quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder); + *remainder = -*remainder; + if (divisor > 0) + quotient = -quotient; + } else { + quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder); + if (divisor < 0) + quotient = -quotient; + } + return quotient; +} +EXPORT_SYMBOL(div_s64_rem); +#endif + +/* + * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder + * @dividend: 64bit dividend + * @divisor: 64bit divisor + * @remainder: 64bit remainder + * + * This implementation is a comparable to algorithm used by div64_u64. + * But this operation, which includes math for calculating the remainder, + * is kept distinct to avoid slowing down the div64_u64 operation on 32bit + * systems. + */ +#ifndef div64_u64_rem +u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder) +{ + u32 high = divisor >> 32; + u64 quot; + + if (high == 0) { + u32 rem32; + quot = div_u64_rem(dividend, divisor, &rem32); + *remainder = rem32; + } else { + int n = fls(high); + quot = div_u64(dividend >> n, divisor >> n); + + if (quot != 0) + quot--; + + *remainder = dividend - quot * divisor; + if (*remainder >= divisor) { + quot++; + *remainder -= divisor; + } + } + + return quot; +} +EXPORT_SYMBOL(div64_u64_rem); +#endif + +/* + * div64_u64 - unsigned 64bit divide with 64bit divisor + * @dividend: 64bit dividend + * @divisor: 64bit divisor + * + * This implementation is a modified version of the algorithm proposed + * by the book 'Hacker's Delight'. The original source and full proof + * can be found here and is available for use without restriction. + * + * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt' + */ +#ifndef div64_u64 +u64 div64_u64(u64 dividend, u64 divisor) +{ + u32 high = divisor >> 32; + u64 quot; + + if (high == 0) { + quot = div_u64(dividend, divisor); + } else { + int n = fls(high); + quot = div_u64(dividend >> n, divisor >> n); + + if (quot != 0) + quot--; + if ((dividend - quot * divisor) >= divisor) + quot++; + } + + return quot; +} +EXPORT_SYMBOL(div64_u64); +#endif + +#ifndef div64_s64 +s64 div64_s64(s64 dividend, s64 divisor) +{ + s64 quot, t; + + quot = div64_u64(abs(dividend), abs(divisor)); + t = (dividend ^ divisor) >> 63; + + return (quot ^ t) - t; +} +EXPORT_SYMBOL(div64_s64); +#endif + +#endif /* BITS_PER_LONG == 32 */ + +/* + * Iterative div/mod for use when dividend is not expected to be much + * bigger than divisor. + */ +#ifndef iter_div_u64_rem +u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) +{ + return __iter_div_u64_rem(dividend, divisor, remainder); +} +EXPORT_SYMBOL(iter_div_u64_rem); +#endif + +#if !defined(mul_u64_add_u64_div_u64) || defined(test_mul_u64_add_u64_div_u64) + +#define mul_add(a, b, c) add_u64_u32(mul_u32_u32(a, b), c) + +#if defined(__SIZEOF_INT128__) && !defined(test_mul_u64_add_u64_div_u64) +static inline u64 mul_u64_u64_add_u64(u64 *p_lo, u64 a, u64 b, u64 c) +{ + /* native 64x64=128 bits multiplication */ + u128 prod = (u128)a * b + c; + + *p_lo = prod; + return prod >> 64; +} +#else +static inline u64 mul_u64_u64_add_u64(u64 *p_lo, u64 a, u64 b, u64 c) +{ + /* perform a 64x64=128 bits multiplication in 32bit chunks */ + u64 x, y, z; + + /* Since (x-1)(x-1) + 2(x-1) == x.x - 1 two u32 can be added to a u64 */ + x = mul_add(a, b, c); + y = mul_add(a, b >> 32, c >> 32); + y = add_u64_u32(y, x >> 32); + z = mul_add(a >> 32, b >> 32, y >> 32); + y = mul_add(a >> 32, b, y); + *p_lo = (y << 32) + (u32)x; + return add_u64_u32(z, y >> 32); +} +#endif + +#ifndef BITS_PER_ITER +#define BITS_PER_ITER (__LONG_WIDTH__ >= 64 ? 32 : 16) +#endif + +#if BITS_PER_ITER == 32 +#define mul_u64_long_add_u64(p_lo, a, b, c) mul_u64_u64_add_u64(p_lo, a, b, c) +#define add_u64_long(a, b) ((a) + (b)) +#else +#undef BITS_PER_ITER +#define BITS_PER_ITER 16 +static inline u32 mul_u64_long_add_u64(u64 *p_lo, u64 a, u32 b, u64 c) +{ + u64 n_lo = mul_add(a, b, c); + u64 n_med = mul_add(a >> 32, b, c >> 32); + + n_med = add_u64_u32(n_med, n_lo >> 32); + *p_lo = n_med << 32 | (u32)n_lo; + return n_med >> 32; +} + +#define add_u64_long(a, b) add_u64_u32(a, b) +#endif + +u64 mul_u64_add_u64_div_u64(u64 a, u64 b, u64 c, u64 d) +{ + unsigned long d_msig, q_digit; + unsigned int reps, d_z_hi; + u64 quotient, n_lo, n_hi; + u32 overflow; + + n_hi = mul_u64_u64_add_u64(&n_lo, a, b, c); + + if (!n_hi) + return div64_u64(n_lo, d); + + if (unlikely(n_hi >= d)) { + /* trigger runtime exception if divisor is zero */ + if (d == 0) { + unsigned long zero = 0; + + OPTIMIZER_HIDE_VAR(zero); + return ~0UL/zero; + } + /* overflow: result is unrepresentable in a u64 */ + return ~0ULL; + } + + /* Left align the divisor, shifting the dividend to match */ + d_z_hi = __builtin_clzll(d); + if (d_z_hi) { + d <<= d_z_hi; + n_hi = n_hi << d_z_hi | n_lo >> (64 - d_z_hi); + n_lo <<= d_z_hi; + } + + reps = 64 / BITS_PER_ITER; + /* Optimise loop count for small dividends */ + if (!(u32)(n_hi >> 32)) { + reps -= 32 / BITS_PER_ITER; + n_hi = n_hi << 32 | n_lo >> 32; + n_lo <<= 32; + } +#if BITS_PER_ITER == 16 + if (!(u32)(n_hi >> 48)) { + reps--; + n_hi = add_u64_u32(n_hi << 16, n_lo >> 48); + n_lo <<= 16; + } +#endif + + /* Invert the dividend so we can use add instead of subtract. */ + n_lo = ~n_lo; + n_hi = ~n_hi; + + /* + * Get the most significant BITS_PER_ITER bits of the divisor. + * This is used to get a low 'guestimate' of the quotient digit. + */ + d_msig = (d >> (64 - BITS_PER_ITER)) + 1; + + /* + * Now do a 'long division' with BITS_PER_ITER bit 'digits'. + * The 'guess' quotient digit can be low and BITS_PER_ITER+1 bits. + * The worst case is dividing ~0 by 0x8000 which requires two subtracts. + */ + quotient = 0; + while (reps--) { + q_digit = (unsigned long)(~n_hi >> (64 - 2 * BITS_PER_ITER)) / d_msig; + /* Shift 'n' left to align with the product q_digit * d */ + overflow = n_hi >> (64 - BITS_PER_ITER); + n_hi = add_u64_u32(n_hi << BITS_PER_ITER, n_lo >> (64 - BITS_PER_ITER)); + n_lo <<= BITS_PER_ITER; + /* Add product to negated divisor */ + overflow += mul_u64_long_add_u64(&n_hi, d, q_digit, n_hi); + /* Adjust for the q_digit 'guestimate' being low */ + while (overflow < 0xffffffff >> (32 - BITS_PER_ITER)) { + q_digit++; + n_hi += d; + overflow += n_hi < d; + } + quotient = add_u64_long(quotient << BITS_PER_ITER, q_digit); + } + + /* + * The above only ensures the remainder doesn't overflow, + * it can still be possible to add (aka subtract) another copy + * of the divisor. + */ + if ((n_hi + d) > n_hi) + quotient++; + return quotient; +} +#if !defined(test_mul_u64_add_u64_div_u64) +EXPORT_SYMBOL(mul_u64_add_u64_div_u64); +#endif +#endif |
