From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754103Ab1DEX4z (ORCPT ); Tue, 5 Apr 2011 19:56:55 -0400 Received: from wolverine02.qualcomm.com ([199.106.114.251]:33983 "EHLO wolverine02.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752777Ab1DEX4o (ORCPT ); Tue, 5 Apr 2011 19:56:44 -0400 X-IronPort-AV: E=McAfee;i="5400,1158,6307"; a="83965973" From: Stephen Boyd To: Russell King Cc: linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Saravana Kannan , Andrew Morton , Mattias Wallin , Linus Walleij Subject: [PATCHv5 1/3] ARM: Translate delay.S into (mostly) C Date: Tue, 5 Apr 2011 16:56:38 -0700 Message-Id: <1302047800-26720-2-git-send-email-sboyd@codeaurora.org> X-Mailer: git-send-email 1.7.5.rc0.131.gfa38c In-Reply-To: <1302047800-26720-1-git-send-email-sboyd@codeaurora.org> References: <1302047800-26720-1-git-send-email-sboyd@codeaurora.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We want to allow machines to override the __delay() implementation at runtime so they can use a timer based __delay() routine. It's easier to do this using C, so let's write udelay and friends in C. We lose the #if 0 code, which according to Russell is used "to make the delay loop more stable and predictable on older CPUs" (see http://article.gmane.org/gmane.linux.kernel/888867 for more info). We shouldn't be too worried though, since we'll soon add functionality allowing a machine to set the __delay() loop themselves, thus allowing machines to resurrect the commented out code should they need it. Nicolas expressed concern that fixed lpj cmdlines will break due to compiler optimizations. That doesn't seem to be the case since before and after this patch I get the same lpj value when running my CPU at 19.2 MHz. That should be sufficiently slow enough to cover any machine running Linux. Reviewed-by: Saravana Kannan Cc: Nicolas Pitre , Signed-off-by: Stephen Boyd --- arch/arm/include/asm/delay.h | 2 +- arch/arm/kernel/armksyms.c | 4 -- arch/arm/lib/delay.S | 69 ------------------------------------------ arch/arm/lib/delay.c | 62 +++++++++++++++++++++++++++++++++++++ 4 files changed, 63 insertions(+), 74 deletions(-) delete mode 100644 arch/arm/lib/delay.S create mode 100644 arch/arm/lib/delay.c diff --git a/arch/arm/include/asm/delay.h b/arch/arm/include/asm/delay.h index b2deda1..ccc5ed5 100644 --- a/arch/arm/include/asm/delay.h +++ b/arch/arm/include/asm/delay.h @@ -8,7 +8,7 @@ #include /* HZ */ -extern void __delay(int loops); +extern void __delay(unsigned long loops); /* * This function intentionally does not exist; if you see references to diff --git a/arch/arm/kernel/armksyms.c b/arch/arm/kernel/armksyms.c index e5e1e538..220dce6 100644 --- a/arch/arm/kernel/armksyms.c +++ b/arch/arm/kernel/armksyms.c @@ -52,10 +52,6 @@ extern void fpundefinstr(void); EXPORT_SYMBOL(__backtrace); - /* platform dependent support */ -EXPORT_SYMBOL(__udelay); -EXPORT_SYMBOL(__const_udelay); - /* networking */ EXPORT_SYMBOL(csum_partial); EXPORT_SYMBOL(csum_partial_copy_from_user); diff --git a/arch/arm/lib/delay.S b/arch/arm/lib/delay.S deleted file mode 100644 index 3c9a05c..0000000 --- a/arch/arm/lib/delay.S +++ /dev/null @@ -1,69 +0,0 @@ -/* - * linux/arch/arm/lib/delay.S - * - * Copyright (C) 1995, 1996 Russell King - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License version 2 as - * published by the Free Software Foundation. - */ -#include -#include -#include - .text - -.LC0: .word loops_per_jiffy -.LC1: .word (2199023*HZ)>>11 - -/* - * r0 <= 2000 - * lpj <= 0x01ffffff (max. 3355 bogomips) - * HZ <= 1000 - */ - -ENTRY(__udelay) - ldr r2, .LC1 - mul r0, r2, r0 -ENTRY(__const_udelay) @ 0 <= r0 <= 0x7fffff06 - mov r1, #-1 - ldr r2, .LC0 - ldr r2, [r2] @ max = 0x01ffffff - add r0, r0, r1, lsr #32-14 - mov r0, r0, lsr #14 @ max = 0x0001ffff - add r2, r2, r1, lsr #32-10 - mov r2, r2, lsr #10 @ max = 0x00007fff - mul r0, r2, r0 @ max = 2^32-1 - add r0, r0, r1, lsr #32-6 - movs r0, r0, lsr #6 - moveq pc, lr - -/* - * loops = r0 * HZ * loops_per_jiffy / 1000000 - * - * Oh, if only we had a cycle counter... - */ - -@ Delay routine -ENTRY(__delay) - subs r0, r0, #1 -#if 0 - movls pc, lr - subs r0, r0, #1 - movls pc, lr - subs r0, r0, #1 - movls pc, lr - subs r0, r0, #1 - movls pc, lr - subs r0, r0, #1 - movls pc, lr - subs r0, r0, #1 - movls pc, lr - subs r0, r0, #1 - movls pc, lr - subs r0, r0, #1 -#endif - bhi __delay - mov pc, lr -ENDPROC(__udelay) -ENDPROC(__const_udelay) -ENDPROC(__delay) diff --git a/arch/arm/lib/delay.c b/arch/arm/lib/delay.c new file mode 100644 index 0000000..daca2be --- /dev/null +++ b/arch/arm/lib/delay.c @@ -0,0 +1,62 @@ +/* + * Originally from linux/arch/arm/lib/delay.S + * + * Copyright (C) 1995, 1996 Russell King + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ +#include +#include + +/* + * loops = usecs * HZ * loops_per_jiffy / 1000000 + * + * Oh, if only we had a cycle counter... + */ +void __delay(unsigned long loops) +{ + asm volatile( + "1: subs %0, %0, #1 \n" + " bhi 1b \n" + : /* No output */ + : "r" (loops) + ); +} +EXPORT_SYMBOL(__delay); + +/* + * 0 <= xloops <= 0x7fffff06 + * loops_per_jiffy <= 0x01ffffff (max. 3355 bogomips) + */ +void __const_udelay(unsigned long xloops) +{ + unsigned long mask = ULONG_MAX; + unsigned long lpj = loops_per_jiffy; + unsigned long loops; + + xloops += mask >> (32 - 14); + xloops >>= 14; /* max = 0x01ffffff */ + + lpj += mask >> (32 - 10); + lpj >>= 10; /* max = 0x0001ffff */ + + loops = lpj * xloops; /* max = 0x00007fff */ + loops += mask >> (32 - 6); + loops >>= 6; /* max = 2^32-1 */ + + if (likely(loops)) + __delay(loops); +} +EXPORT_SYMBOL(__const_udelay); + +/* + * usecs <= 2000 + * HZ <= 1000 + */ +void __udelay(unsigned long usecs) +{ + __const_udelay(usecs * ((2199023*HZ)>>11)); +} +EXPORT_SYMBOL(__udelay); -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.