xref: /openbmc/linux/arch/arm/include/asm/div64.h (revision f5c27da4)
1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __ASM_ARM_DIV64
3 #define __ASM_ARM_DIV64
4 
5 #include <linux/types.h>
6 #include <asm/compiler.h>
7 
8 /*
9  * The semantics of __div64_32() are:
10  *
11  * uint32_t __div64_32(uint64_t *n, uint32_t base)
12  * {
13  * 	uint32_t remainder = *n % base;
14  * 	*n = *n / base;
15  * 	return remainder;
16  * }
17  *
18  * In other words, a 64-bit dividend with a 32-bit divisor producing
19  * a 64-bit result and a 32-bit remainder.  To accomplish this optimally
20  * we override the generic version in lib/div64.c to call our __do_div64
21  * assembly implementation with completely non standard calling convention
22  * for arguments and results (beware).
23  */
24 static inline uint32_t __div64_32(uint64_t *n, uint32_t base)
25 {
26 	register unsigned int __base      asm("r4") = base;
27 	register unsigned long long __n   asm("r0") = *n;
28 	register unsigned long long __res asm("r2");
29 	unsigned int __rem;
30 	asm(	__asmeq("%0", "r0")
31 		__asmeq("%1", "r2")
32 		__asmeq("%2", "r4")
33 		"bl	__do_div64"
34 		: "+r" (__n), "=r" (__res)
35 		: "r" (__base)
36 		: "ip", "lr", "cc");
37 	__rem = __n >> 32;
38 	*n = __res;
39 	return __rem;
40 }
41 #define __div64_32 __div64_32
42 
43 #if !defined(CONFIG_AEABI)
44 
45 /*
46  * In OABI configurations, some uses of the do_div function
47  * cause gcc to run out of registers. To work around that,
48  * we can force the use of the out-of-line version for
49  * configurations that build a OABI kernel.
50  */
51 #define do_div(n, base) __div64_32(&(n), base)
52 
53 #else
54 
55 static inline uint64_t __arch_xprod_64(uint64_t m, uint64_t n, bool bias)
56 {
57 	unsigned long long res;
58 	register unsigned int tmp asm("ip") = 0;
59 
60 	if (!bias) {
61 		asm (	"umull	%Q0, %R0, %Q1, %Q2\n\t"
62 			"mov	%Q0, #0"
63 			: "=&r" (res)
64 			: "r" (m), "r" (n)
65 			: "cc");
66 	} else if (!(m & ((1ULL << 63) | (1ULL << 31)))) {
67 		res = m;
68 		asm (	"umlal	%Q0, %R0, %Q1, %Q2\n\t"
69 			"mov	%Q0, #0"
70 			: "+&r" (res)
71 			: "r" (m), "r" (n)
72 			: "cc");
73 	} else {
74 		asm (	"umull	%Q0, %R0, %Q2, %Q3\n\t"
75 			"cmn	%Q0, %Q2\n\t"
76 			"adcs	%R0, %R0, %R2\n\t"
77 			"adc	%Q0, %1, #0"
78 			: "=&r" (res), "+&r" (tmp)
79 			: "r" (m), "r" (n)
80 			: "cc");
81 	}
82 
83 	if (!(m & ((1ULL << 63) | (1ULL << 31)))) {
84 		asm (	"umlal	%R0, %Q0, %R1, %Q2\n\t"
85 			"umlal	%R0, %Q0, %Q1, %R2\n\t"
86 			"mov	%R0, #0\n\t"
87 			"umlal	%Q0, %R0, %R1, %R2"
88 			: "+&r" (res)
89 			: "r" (m), "r" (n)
90 			: "cc");
91 	} else {
92 		asm (	"umlal	%R0, %Q0, %R2, %Q3\n\t"
93 			"umlal	%R0, %1, %Q2, %R3\n\t"
94 			"mov	%R0, #0\n\t"
95 			"adds	%Q0, %1, %Q0\n\t"
96 			"adc	%R0, %R0, #0\n\t"
97 			"umlal	%Q0, %R0, %R2, %R3"
98 			: "+&r" (res), "+&r" (tmp)
99 			: "r" (m), "r" (n)
100 			: "cc");
101 	}
102 
103 	return res;
104 }
105 #define __arch_xprod_64 __arch_xprod_64
106 
107 #include <asm-generic/div64.h>
108 
109 #endif
110 
111 #endif
112