[PATCH] ftape support for x86_64

We have this patch that adds ftape support for x86_64 and cleans up the
alpha support a little.  The comments look like Vojtech did the x86_64 part
and I guess the alpha bits are from Herbert Xu.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/char/ftape/lowlevel/ftape-calibr.c

@@ -31,7 +31,10 @@
 #include <asm/io.h>
 #if defined(__alpha__)
 # include <asm/hwrpb.h>
-#elif defined(__i386__) || defined(__x86_64__)
+#elif defined(__x86_64__)
+# include <asm/msr.h>
+# include <asm/timex.h>
+#elif defined(__i386__)
 # include <linux/timex.h>
 #endif
 #include <linux/ftape.h>
@@ -45,7 +48,7 @@
 # error Ftape is not implemented for this architecture!
 #endif
 
-#if defined(__alpha__)
+#if defined(__alpha__) || defined(__x86_64__)
 static unsigned long ps_per_cycle = 0;
 #endif
 
@@ -72,7 +75,18 @@ unsigned int ftape_timestamp(void)
 
 	asm volatile ("rpcc %0" : "=r" (r));
 	return r;
-#elif defined(__i386__) || defined(__x86_64__)
+#elif defined(__x86_64__)
+	unsigned long r;
+	rdtscl(r);
+	return r;
+#elif defined(__i386__)
+
+/*
+ * Note that there is some time between counter underflowing and jiffies
+ * increasing, so the code below won't always give correct output.
+ * -Vojtech
+ */
+
 	unsigned long flags;
 	__u16 lo;
 	__u16 hi;
@@ -89,9 +103,9 @@ unsigned int ftape_timestamp(void)
 
 static unsigned int short_ftape_timestamp(void)
 {
-#if defined(__alpha__)
+#if defined(__alpha__) || defined(__x86_64__)
 	return ftape_timestamp();
-#elif defined(__i386__) || defined(__x86_64__)
+#elif defined(__i386__)
 	unsigned int count;
  	unsigned long flags;
  
@@ -106,9 +120,9 @@ static unsigned int short_ftape_timestamp(void)
 
 static unsigned int diff(unsigned int t0, unsigned int t1)
 {
-#if defined(__alpha__)
-	return (t1 <= t0) ? t1 + (1UL << 32) - t0 : t1 - t0;
-#elif defined(__i386__) || defined(__x86_64__)
+#if defined(__alpha__) || defined(__x86_64__)
+	return (t1 - t0);
+#elif defined(__i386__)
 	/*
 	 * This is tricky: to work for both short and full ftape_timestamps
 	 * we'll have to discriminate between these.
@@ -122,9 +136,9 @@ static unsigned int diff(unsigned int t0, unsigned int t1)
 
 static unsigned int usecs(unsigned int count)
 {
-#if defined(__alpha__)
+#if defined(__alpha__) || defined(__x86_64__)
 	return (ps_per_cycle * count) / 1000000UL;
-#elif defined(__i386__) || defined(__x86_64__)
+#elif defined(__i386__)
 	return (10000 * count) / ((CLOCK_TICK_RATE + 50) / 100);
 #endif
 }
@@ -163,38 +177,13 @@ static void time_inb(void)
 
 static void init_clock(void)
 {
-#if defined(__i386__) || defined(__x86_64__)
-	unsigned int t;
-	int i;
 	TRACE_FUN(ft_t_any);
 
-	/*  Haven't studied on why, but there sometimes is a problem
-	 *  with the tick timer readout. The two bytes get swapped.
-	 *  This hack solves that problem by doing one extra input.
-	 */
-	for (i = 0; i < 1000; ++i) {
-		t = short_ftape_timestamp();
-		if (t > LATCH) {
-			inb_p(0x40);	/* get in sync again */
-			TRACE(ft_t_warn, "clock counter fixed");
-			break;
-		}
-	}
+#if defined(__x86_64__)
+	ps_per_cycle = 1000000000UL / cpu_khz;
 #elif defined(__alpha__)
-#if CONFIG_FT_ALPHA_CLOCK == 0
-#error You must define and set CONFIG_FT_ALPHA_CLOCK in 'make config' !
-#endif
 	extern struct hwrpb_struct *hwrpb;
-	TRACE_FUN(ft_t_any);
-
-	if (hwrpb->cycle_freq != 0) {
-		ps_per_cycle = (1000*1000*1000*1000UL) / hwrpb->cycle_freq;
-	} else {
-		/*
-		 * HELP:  Linux 2.0.x doesn't set cycle_freq on my noname !
-		 */
-		ps_per_cycle = (1000*1000*1000*1000UL) / CONFIG_FT_ALPHA_CLOCK;
-	}
+	ps_per_cycle = (1000*1000*1000*1000UL) / hwrpb->cycle_freq;
 #endif
 	TRACE_EXIT;
 }
@@ -213,7 +202,7 @@ void ftape_calibrate(char *name,
 	unsigned int tc = 0;
 	unsigned int count;
 	unsigned int time;
-#if defined(__i386__) || defined(__x86_64__)
+#if defined(__i386__)
 	unsigned int old_tc = 0;
 	unsigned int old_count = 1;
 	unsigned int old_time = 1;
@@ -255,7 +244,7 @@ void ftape_calibrate(char *name,
 		tc = (1000 * time) / (count - 1);
 		TRACE(ft_t_any, "once:%3d us,%6d times:%6d us, TC:%5d ns",
 			usecs(once), count - 1, usecs(multiple), tc);
-#if defined(__alpha__)
+#if defined(__alpha__) || defined(__x86_64__)
 		/*
 		 * Increase the calibration count exponentially until the
 		 * calibration time exceeds 100 ms.
@@ -263,7 +252,7 @@ void ftape_calibrate(char *name,
 		if (time >= 100*1000) {
 			break;
 		}
-#elif defined(__i386__) || defined(__x86_64__)
+#elif defined(__i386__)
 		/*
 		 * increase the count until the resulting time nears 2/HZ,
 		 * then the tc will drop sharply because we lose LATCH counts.