kMessage-ID: <47011930.60100@reinelt.co.at>
Date: Mon, 01 Oct 2007 17:58:40 +0200
From: Michael Reinelt <michael@reinelt.co.at>
Subject: [Lcd4linux-devel] asm/msr.h inclusion and RDTSC stuff removed

Hi there,

I just committed a changeset where I removed the whole RDTSC delay loop 
stuff, and therefore lcd4linux does no longer need asm/msr.h

Instead, a gettimeofday() delay loop will be used when necessary.

The rdtsc stuff worked fine, but had two major disadvantages: It did not 
work with variable CPU frequencies, and latest kernels do no longer 
offer the rdtsc() macro.

The changeset has been committed to trunk, and will be backported to the 
0.10.1 branch as soon as I get some positive feedback 8or at least I 
don't get any negative feedback)


bye, Michael

-- 
Michael Reinelt <michael@reinelt.co.at>
http://home.pages.at/reinelt
GPG-Key 0xDF13BA50
ICQ #288386781

Index: configure.in
===================================================================
--- lcd4linux-0.10.1-RC2/configure.in.orig
+++ lcd4linux-0.10.1-RC2/configure.in
@@ -99,7 +99,6 @@ AC_HEADER_STDC
 AC_CHECK_HEADERS([arpa/inet.h fcntl.h netdb.h netinet/in.h stdlib.h string.h sys/ioctl.h sys/socket.h sys/time.h sys/vfs.h syslog.h termios.h unistd.h])
 AC_CHECK_HEADERS(sys/io.h asm/io.h)
 AC_CHECK_HEADERS(linux/parport.h linux/ppdev.h)
-AC_CHECK_HEADERS(asm/msr.h)
 
 # Checks for typedefs, structures, and compiler characteristics.
 AC_C_CONST
Index: udelay.c
===================================================================
--- lcd4linux-0.10.1-RC2/udelay.c.orig
+++ lcd4linux-0.10.1-RC2/udelay.c
@@ -55,11 +55,6 @@
 #include <string.h>
 #include <sys/time.h>
 
-#ifdef HAVE_ASM_MSR_H
-#define u32 unsigned int
-#include <asm/msr.h>
-#endif
-
 
 #include "debug.h"
 #include "cfg.h"
@@ -67,79 +62,10 @@
 #include "udelay.h"
 
 
-static unsigned int ticks_per_usec = 0;
-
-
-static void getCPUinfo(int *hasTSC, double *MHz)
-{
-    int fd;
-    char buffer[4096], *p;
-
-    *hasTSC = 0;
-    *MHz = -1;
-
-    fd = open("/proc/cpuinfo", O_RDONLY);
-    if (fd == -1) {
-	error("udelay: open(/proc/cpuinfo) failed: %s", strerror(errno));
-	return;
-    }
-    if (read(fd, &buffer, sizeof(buffer) - 1) == -1) {
-	error("udelay: read(/proc/cpuinfo) failed: %s", strerror(errno));
-	close(fd);
-	return;
-    }
-    close(fd);
-
-    p = strstr(buffer, "flags");
-    if (p == NULL) {
-	info("udelay: /proc/cpuinfo has no 'flags' line");
-    } else {
-	p = strstr(p, "tsc");
-	if (p == NULL) {
-	    info("udelay: CPU does not support Time Stamp Counter");
-	} else {
-	    info("udelay: CPU supports Time Stamp Counter");
-	    *hasTSC = 1;
-	}
-    }
-
-    p = strstr(buffer, "cpu MHz");
-    if (p == NULL) {
-	info("udelay: /proc/cpuinfo has no 'cpu MHz' line");
-    } else {
-	if (sscanf(p + 7, " : %lf", MHz) != 1) {
-	    error("udelay: parse(/proc/cpuinfo) failed: unknown 'cpu MHz' format");
-	    *MHz = -1;
-	} else {
-	    info("udelay: CPU runs at %f MHz", *MHz);
-	}
-    }
-
-}
-
 
 void udelay_init(void)
 {
-#ifdef HAVE_ASM_MSR_H
-
-    int tsc;
-    double mhz;
-
-    getCPUinfo(&tsc, &mhz);
-
-    if (tsc && mhz > 0.0) {
-	ticks_per_usec = ceil(mhz);
-	info("udelay: using TSC delay loop, %u ticks per microsecond", ticks_per_usec);
-    } else
-#else
-    error("udelay: The file 'include/asm/msr.h' was missing at compile time.");
-    error("udelay: Even if your CPU supports TSC, it will not be used!");
-    error("udelay: You *really* should install msr.h and recompile LCD4linux!");
-#endif
-    {
-	ticks_per_usec = 0;
-	info("udelay: using gettimeofday() delay loop");
-    }
+    info("udelay: using gettimeofday() delay loop");
 }
 
 
@@ -172,37 +98,17 @@ unsigned long timing(const char *driver,
 void ndelay(const unsigned long nsec)
 {
 
-#ifdef HAVE_ASM_MSR_H
-
-    if (ticks_per_usec) {
+    struct timeval now, end;
 
-	unsigned int t1, t2;
-	unsigned long tsc;
-
-	tsc = (nsec * ticks_per_usec + 999) / 1000;
-
-	rdtscl(t1);
-	do {
-	    rep_nop();
-	    rdtscl(t2);
-	} while ((t2 - t1) < tsc);
-
-    } else
-#endif
-
-    {
-	struct timeval now, end;
-
-	gettimeofday(&end, NULL);
-	end.tv_usec += (nsec + 999) / 1000;
-	while (end.tv_usec > 1000000) {
-	    end.tv_usec -= 1000000;
-	    end.tv_sec++;
-	}
-
-	do {
-	    rep_nop();
-	    gettimeofday(&now, NULL);
-	} while (now.tv_sec == end.tv_sec ? now.tv_usec < end.tv_usec : now.tv_sec < end.tv_sec);
+    gettimeofday(&end, NULL);
+    end.tv_usec += (nsec + 999) / 1000;
+    while (end.tv_usec > 1000000) {
+	end.tv_usec -= 1000000;
+	end.tv_sec++;
     }
+
+    do {
+	rep_nop();
+	gettimeofday(&now, NULL);
+    } while (now.tv_sec == end.tv_sec ? now.tv_usec < end.tv_usec : now.tv_sec < end.tv_sec);
 }