linux-kernel - [RFC PATCH] x86: Add safe_udelay() and safe

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Message-ID: <4D2CFEAD.6070206@kernel.org>
Date:	Tue, 11 Jan 2011 17:06:53 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	Greg KH <greg@...ah.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux.com>, Tejun Heo <tj@...nel.org>
Subject: [RFC PATCH] x86: Add safe_udelay() and safe_msleep()


We need to use those function in early-quirk stage with code that is shared with
later stage.

for x86, normal udelay() will need to wait per_cpu(cpu_info) is allocated... that i
after smp_prepare_cpus(), because it need to use percpu.loops_per_jiffy.

Also msleep() will need to wait schedular is ready.

Try to have one early version udelay that use loops_per_jiffy directly.
and early msleep is just early delay.

This patch will set safe_udelay to early in x86 early arch code, and then init/main.c
will set them back.

Signed-off-by: Yinghai Lu <yinghai@...nel.org>

---
 arch/x86/include/asm/delay.h |    3 +++
 arch/x86/kernel/setup.c      |    4 ++++
 arch/x86/lib/delay.c         |   28 ++++++++++++++++++++++++++++
 include/linux/delay.h        |    2 ++
 init/main.c                  |    6 ++++++
 5 files changed, 43 insertions(+)

Index: linux-2.6/arch/x86/include/asm/delay.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/delay.h
+++ linux-2.6/arch/x86/include/asm/delay.h
@@ -28,4 +28,7 @@ extern void __delay(unsigned long loops)
 
 void use_tsc_delay(void);
 
+extern void __early_udelay(unsigned long usecs);
+extern void __early_msleep(unsigned int msecs);
+
 #endif /* _ASM_X86_DELAY_H */
Index: linux-2.6/arch/x86/kernel/setup.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/setup.c
+++ linux-2.6/arch/x86/kernel/setup.c
@@ -853,6 +853,10 @@ void __init setup_arch(char **cmdline_p)
 
 	dmi_scan_machine();
 
+	/* for early using */
+	safe_udelay = __early_udelay;
+	safe_msleep = __early_msleep;
+
 	/*
 	 * VMware detection requires dmi to be available, so this
 	 * needs to be done after dmi_scan_machine, for the BP.
Index: linux-2.6/arch/x86/lib/delay.c
===================================================================
--- linux-2.6.orig/arch/x86/lib/delay.c
+++ linux-2.6/arch/x86/lib/delay.c
@@ -138,3 +138,31 @@ void __ndelay(unsigned long nsecs)
 	__const_udelay(nsecs * 0x00005); /* 2**32 / 1000000000 (rounded up) */
 }
 EXPORT_SYMBOL(__ndelay);
+
+/* before cpu_info.loops_per_jiffy get set */
+static inline void __early_const_udelay(unsigned long xloops)
+{
+	int d0;
+
+	xloops *= 4;
+	asm("mull %%edx"
+		: "=d" (xloops), "=&a" (d0)
+		: "1" (xloops), "0"
+		(loops_per_jiffy * (HZ/4)));
+
+	delay_loop(++xloops);
+}
+
+/* usecs need to < 2000 */
+void __init __early_udelay(unsigned long usecs)
+{
+	/* 2**32 / 1000000 (rounded up) */
+	__early_const_udelay(usecs * 0x000010c7);
+}
+
+/* before schedular is there */
+void __init __early_msleep(unsigned int msecs)
+{
+	while (msecs--)
+		__early_udelay(1000);
+}
Index: linux-2.6/include/linux/delay.h
===================================================================
--- linux-2.6.orig/include/linux/delay.h
+++ linux-2.6/include/linux/delay.h
@@ -52,4 +52,6 @@ static inline void ssleep(unsigned int s
 	msleep(seconds * 1000);
 }
 
+extern void (*safe_udelay)(unsigned long);
+extern void (*safe_msleep)(unsigned int);
 #endif /* defined(_LINUX_DELAY_H) */
Index: linux-2.6/init/main.c
===================================================================
--- linux-2.6.orig/init/main.c
+++ linux-2.6/init/main.c
@@ -240,6 +240,9 @@ unsigned long loops_per_jiffy = (1<<12);
 
 EXPORT_SYMBOL(loops_per_jiffy);
 
+void (*safe_udelay)(unsigned long) = __udelay;
+void (*safe_msleep)(unsigned int) = msleep;
+
 static int __init debug_kernel(char *str)
 {
 	console_loglevel = 10;
@@ -879,6 +882,9 @@ static int __init kernel_init(void * unu
 	cad_pid = task_pid(current);
 
 	smp_prepare_cpus(setup_max_cpus);
+	/* set them back, x86 use it for early delay*/
+	safe_udelay = __udelay;
+	safe_msleep = msleep;
 
 	do_pre_smp_initcalls();
 	lockup_detector_init();
--
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