Orange Pi5 kernel

^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  1) /* SPDX-License-Identifier: GPL-2.0-only */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  2) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  3)  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  4)  *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  5)  * Delay routines using pre computed loops_per_jiffy value.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  6)  *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  7)  * vineetg: Feb 2012
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  8)  *  -Rewrote in "C" to avoid dealing with availability of H/w MPY
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  9)  *  -Also reduced the num of MPY operations from 3 to 2
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10)  *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11)  * Amit Bhor: Codito Technologies 2004
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12)  */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) #ifndef __ASM_ARC_UDELAY_H
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) #define __ASM_ARC_UDELAY_H
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) #include <asm-generic/types.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) #include <asm/param.h>		/* HZ */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) extern unsigned long loops_per_jiffy;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) static inline void __delay(unsigned long loops)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) 	__asm__ __volatile__(
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) 	"	mov lp_count, %0	\n"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) 	"	lp  1f			\n"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) 	"	nop			\n"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) 	"1:				\n"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) 	:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30)         : "r"(loops)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31)         : "lp_count");
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) extern void __bad_udelay(void);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37)  * Normal Math for computing loops in "N" usecs
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38)  *  -we have precomputed @loops_per_jiffy
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39)  *  -1 sec has HZ jiffies
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40)  * loops per "N" usecs = ((loops_per_jiffy * HZ / 1000000) * N)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41)  *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42)  * Approximate Division by multiplication:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43)  *  -Mathematically if we multiply and divide a number by same value the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44)  *   result remains unchanged:  In this case, we use 2^32
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45)  *  -> (loops_per_N_usec * 2^32 ) / 2^32
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46)  *  -> (((loops_per_jiffy * HZ / 1000000) * N) * 2^32) / 2^32
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47)  *  -> (loops_per_jiffy * HZ * N * 4295) / 2^32
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48)  *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49)  *  -Divide by 2^32 is very simply right shift by 32
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50)  *  -We simply need to ensure that the multiply per above eqn happens in
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51)  *   64-bit precision (if CPU doesn't support it - gcc can emaulate it)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52)  */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) static inline void __udelay(unsigned long usecs)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) 	unsigned long loops;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58) 	/* (u64) cast ensures 64 bit MPY - real or emulated
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) 	 * HZ * 4295 is pre-evaluated by gcc - hence only 2 mpy ops
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) 	 */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) 	loops = ((u64) usecs * 4295 * HZ * loops_per_jiffy) >> 32;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63) 	__delay(loops);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66) #define udelay(n) (__builtin_constant_p(n) ? ((n) > 20000 ? __bad_udelay() \
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) 				: __udelay(n)) : __udelay(n))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69) #endif /* __ASM_ARC_UDELAY_H */