2 files changed, 64 insertions, 1 deletions

diff --git a/drivers/s390/Makefile b/drivers/s390/Makefile
index 9803c9352d78..5a888704a8d0 100644
--- a/drivers/s390/Makefile
+++ b/drivers/s390/Makefile
@@ -2,6 +2,8 @@
 # Makefile for the S/390 specific device drivers
 #
 
+CFLAGS_sysinfo.o += -Iinclude/math-emu -Iarch/s390/math-emu -w
+
 obj-y += s390mach.o sysinfo.o s390_rdev.o
 obj-y += cio/ block/ char/ crypto/ net/ scsi/
 
diff --git a/drivers/s390/sysinfo.c b/drivers/s390/sysinfo.c
index 1e788e815ce7..090743d2f914 100644
--- a/drivers/s390/sysinfo.c
+++ b/drivers/s390/sysinfo.c
@@ -9,8 +9,14 @@
 #include <linux/mm.h>
 #include <linux/proc_fs.h>
 #include <linux/init.h>
+#include <linux/delay.h>
 #include <asm/ebcdic.h>
 
+/* Sigh, math-emu. Don't ask. */
+#include <asm/sfp-util.h>
+#include <math-emu/soft-fp.h>
+#include <math-emu/single.h>
+
 struct sysinfo_1_1_1 {
         char reserved_0[32];
         char manufacturer[16];
@@ -198,7 +204,7 @@ static int stsi_1_2_2(struct sysinfo_1_2_2 *info, char *page, int len)
                  * if the higher order 8 bits are not zero. Printing
                  * a floating point number in the kernel is a no-no,
                  * always print the number as 32 bit unsigned integer.
-                 * The user-space needs to know about the stange
+                 * The user-space needs to know about the strange
                  * encoding of the alternate cpu capability.
                  */
                 len += sprintf(page + len, "Capability:           %u %u\n",
@@ -351,3 +357,58 @@ static __init int create_proc_sysinfo(void)
 
 __initcall(create_proc_sysinfo);
 
+/*
+ * CPU capability might have changed. Therefore recalculate loops_per_jiffy.
+ */
+void s390_adjust_jiffies(void)
+{
+        struct sysinfo_1_2_2 *info;
+        const unsigned int fmil = 0x4b189680;   /* 1e7 as 32-bit float. */
+        FP_DECL_S(SA); FP_DECL_S(SB); FP_DECL_S(SR);
+        FP_DECL_EX;
+        unsigned int capability;
+
+        info = (void *) get_zeroed_page(GFP_KERNEL);
+        if (!info)
+                return;
+
+        if (stsi(info, 1, 2, 2) != -ENOSYS) {
+                /*
+                 * Major sigh. The cpu capability encoding is "special".
+                 * If the first 9 bits of info->capability are 0 then it
+                 * is a 32 bit unsigned integer in the range 0 .. 2^23.
+                 * If the first 9 bits are != 0 then it is a 32 bit float.
+                 * In addition a lower value indicates a proportionally
+                 * higher cpu capacity. Bogomips are the other way round.
+                 * To get to a halfway suitable number we divide 1e7
+                 * by the cpu capability number. Yes, that means a floating
+                 * point division .. math-emu here we come :-)
+                 */
+                FP_UNPACK_SP(SA, &fmil);
+                if ((info->capability >> 23) == 0)
+                        FP_FROM_INT_S(SB, info->capability, 32, int);
+                else
+                        FP_UNPACK_SP(SB, &info->capability);
+                FP_DIV_S(SR, SA, SB);
+                FP_TO_INT_S(capability, SR, 32, 0);
+        } else
+                /*
+                 * Really old machine without stsi block for basic
+                 * cpu information. Report 42.0 bogomips.
+                 */
+                capability = 42;
+        loops_per_jiffy = capability * (500000/HZ);
+        free_page((unsigned long) info);
+}
+
+/*
+ * calibrate the delay loop
+ */
+void __init calibrate_delay(void)
+{
+        s390_adjust_jiffies();
+        /* Print the good old Bogomips line .. */
+        printk(KERN_DEBUG "Calibrating delay loop (skipped)... "
+               "%lu.%02lu BogoMIPS preset\n", loops_per_jiffy/(500000/HZ),
+               (loops_per_jiffy/(5000/HZ)) % 100);
+}