From ace9429bb58fd418f0c81d4c2835699bddf6bde6 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Thu, 11 Apr 2024 10:27:49 +0200 Subject: Adding upstream version 6.6.15. Signed-off-by: Daniel Baumann --- arch/arc/include/asm/delay.h | 69 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+) create mode 100644 arch/arc/include/asm/delay.h (limited to 'arch/arc/include/asm/delay.h') diff --git a/arch/arc/include/asm/delay.h b/arch/arc/include/asm/delay.h new file mode 100644 index 0000000000..54db798f0a --- /dev/null +++ b/arch/arc/include/asm/delay.h @@ -0,0 +1,69 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) + * + * Delay routines using pre computed loops_per_jiffy value. + * + * vineetg: Feb 2012 + * -Rewrote in "C" to avoid dealing with availability of H/w MPY + * -Also reduced the num of MPY operations from 3 to 2 + * + * Amit Bhor: Codito Technologies 2004 + */ + +#ifndef __ASM_ARC_UDELAY_H +#define __ASM_ARC_UDELAY_H + +#include +#include /* HZ */ + +extern unsigned long loops_per_jiffy; + +static inline void __delay(unsigned long loops) +{ + __asm__ __volatile__( + " mov lp_count, %0 \n" + " lp 1f \n" + " nop \n" + "1: \n" + : + : "r"(loops) + : "lp_count"); +} + +extern void __bad_udelay(void); + +/* + * Normal Math for computing loops in "N" usecs + * -we have precomputed @loops_per_jiffy + * -1 sec has HZ jiffies + * loops per "N" usecs = ((loops_per_jiffy * HZ / 1000000) * N) + * + * Approximate Division by multiplication: + * -Mathematically if we multiply and divide a number by same value the + * result remains unchanged: In this case, we use 2^32 + * -> (loops_per_N_usec * 2^32 ) / 2^32 + * -> (((loops_per_jiffy * HZ / 1000000) * N) * 2^32) / 2^32 + * -> (loops_per_jiffy * HZ * N * 4295) / 2^32 + * + * -Divide by 2^32 is very simply right shift by 32 + * -We simply need to ensure that the multiply per above eqn happens in + * 64-bit precision (if CPU doesn't support it - gcc can emaulate it) + */ + +static inline void __udelay(unsigned long usecs) +{ + unsigned long loops; + + /* (u64) cast ensures 64 bit MPY - real or emulated + * HZ * 4295 is pre-evaluated by gcc - hence only 2 mpy ops + */ + loops = ((u64) usecs * 4295 * HZ * loops_per_jiffy) >> 32; + + __delay(loops); +} + +#define udelay(n) (__builtin_constant_p(n) ? ((n) > 20000 ? __bad_udelay() \ + : __udelay(n)) : __udelay(n)) + +#endif /* __ASM_ARC_UDELAY_H */ -- cgit v1.2.3