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authorLinus Torvalds <torvalds@linux-foundation.org>2026-08-23 13:28:57 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2026-08-23 13:28:57 -0700
commit4352b8aee98005853aa63f57d6377282de17a33f (patch)
tree27614d7a9ef05c32d089004e104364ce42324837 /arch/arm/lib/div64.S
downloadlinux-stable-4352b8aee98005853aa63f57d6377282de17a33f.tar.gz
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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 ...
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+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * linux/arch/arm/lib/div64.S
+ *
+ * Optimized computation of 64-bit dividend / 32-bit divisor
+ *
+ * Author: Nicolas Pitre
+ * Created: Oct 5, 2003
+ * Copyright: Monta Vista Software, Inc.
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+#include <asm/unwind.h>
+
+#ifdef __ARMEB__
+#define xh r0
+#define xl r1
+#define yh r2
+#define yl r3
+#else
+#define xl r0
+#define xh r1
+#define yl r2
+#define yh r3
+#endif
+
+/*
+ * __do_div64: perform a division with 64-bit dividend and 32-bit divisor.
+ *
+ * Note: Calling convention is totally non standard for optimal code.
+ * This is meant to be used by do_div() from include/asm/div64.h only.
+ *
+ * Input parameters:
+ * xh-xl = dividend (clobbered)
+ * r4 = divisor (preserved)
+ *
+ * Output values:
+ * yh-yl = result
+ * xh = remainder
+ *
+ * Clobbered regs: xl, ip
+ */
+
+ENTRY(__do_div64)
+UNWIND(.fnstart)
+
+ @ Test for easy paths first.
+ subs ip, r4, #1
+ bls 9f @ divisor is 0 or 1
+ tst ip, r4
+ beq 8f @ divisor is power of 2
+
+ @ See if we need to handle upper 32-bit result.
+ cmp xh, r4
+ mov yh, #0
+ blo 3f
+
+ @ Align divisor with upper part of dividend.
+ @ The aligned divisor is stored in yl preserving the original.
+ @ The bit position is stored in ip.
+
+#if __LINUX_ARM_ARCH__ >= 5
+
+ clz yl, r4
+ clz ip, xh
+ sub yl, yl, ip
+ mov ip, #1
+ mov ip, ip, lsl yl
+ mov yl, r4, lsl yl
+
+#else
+
+ mov yl, r4
+ mov ip, #1
+1: cmp yl, #0x80000000
+ cmpcc yl, xh
+ movcc yl, yl, lsl #1
+ movcc ip, ip, lsl #1
+ bcc 1b
+
+#endif
+
+ @ The division loop for needed upper bit positions.
+ @ Break out early if dividend reaches 0.
+2: cmp xh, yl
+ orrcs yh, yh, ip
+ subscs xh, xh, yl
+ movsne ip, ip, lsr #1
+ mov yl, yl, lsr #1
+ bne 2b
+
+ @ See if we need to handle lower 32-bit result.
+3: cmp xh, #0
+ mov yl, #0
+ cmpeq xl, r4
+ movlo xh, xl
+ retlo lr
+
+ @ The division loop for lower bit positions.
+ @ Here we shift remainer bits leftwards rather than moving the
+ @ divisor for comparisons, considering the carry-out bit as well.
+ mov ip, #0x80000000
+4: movs xl, xl, lsl #1
+ adcs xh, xh, xh
+ beq 6f
+ cmpcc xh, r4
+5: orrcs yl, yl, ip
+ subcs xh, xh, r4
+ movs ip, ip, lsr #1
+ bne 4b
+ ret lr
+
+ @ The top part of remainder became zero. If carry is set
+ @ (the 33th bit) this is a false positive so resume the loop.
+ @ Otherwise, if lower part is also null then we are done.
+6: bcs 5b
+ cmp xl, #0
+ reteq lr
+
+ @ We still have remainer bits in the low part. Bring them up.
+
+#if __LINUX_ARM_ARCH__ >= 5
+
+ clz xh, xl @ we know xh is zero here so...
+ add xh, xh, #1
+ mov xl, xl, lsl xh
+ mov ip, ip, lsr xh
+
+#else
+
+7: movs xl, xl, lsl #1
+ mov ip, ip, lsr #1
+ bcc 7b
+
+#endif
+
+ @ Current remainder is now 1. It is worthless to compare with
+ @ divisor at this point since divisor can not be smaller than 3 here.
+ @ If possible, branch for another shift in the division loop.
+ @ If no bit position left then we are done.
+ movs ip, ip, lsr #1
+ mov xh, #1
+ bne 4b
+ ret lr
+
+8: @ Division by a power of 2: determine what that divisor order is
+ @ then simply shift values around
+
+#if __LINUX_ARM_ARCH__ >= 5
+
+ clz ip, r4
+ rsb ip, ip, #31
+
+#else
+
+ mov yl, r4
+ cmp r4, #(1 << 16)
+ mov ip, #0
+ movhs yl, yl, lsr #16
+ movhs ip, #16
+
+ cmp yl, #(1 << 8)
+ movhs yl, yl, lsr #8
+ addhs ip, ip, #8
+
+ cmp yl, #(1 << 4)
+ movhs yl, yl, lsr #4
+ addhs ip, ip, #4
+
+ cmp yl, #(1 << 2)
+ addhi ip, ip, #3
+ addls ip, ip, yl, lsr #1
+
+#endif
+
+ mov yh, xh, lsr ip
+ mov yl, xl, lsr ip
+ rsb ip, ip, #32
+ ARM( orr yl, yl, xh, lsl ip )
+ THUMB( lsl xh, xh, ip )
+ THUMB( orr yl, yl, xh )
+ mov xh, xl, lsl ip
+ mov xh, xh, lsr ip
+ ret lr
+
+ @ eq -> division by 1: obvious enough...
+9: moveq yl, xl
+ moveq yh, xh
+ moveq xh, #0
+ reteq lr
+UNWIND(.fnend)
+
+UNWIND(.fnstart)
+UNWIND(.pad #4)
+UNWIND(.save {lr})
+Ldiv0_64:
+ @ Division by 0:
+ str lr, [sp, #-8]!
+ bl __div0
+
+ @ as wrong as it could be...
+ mov yl, #0
+ mov yh, #0
+ mov xh, #0
+ ldr pc, [sp], #8
+
+UNWIND(.fnend)
+ENDPROC(__do_div64)