parisc: Reorder TLB flush timing calculation

On boot (mostly reboot), my c8000 sometimes crashes after it prints the
TLB flush threshold.  The lockup is hard.  The front LED flashes red and
the box must be unplugged to reset the error.

I noticed that when the crash occurs the TLB flush threshold is about
one quarter what it is on a successful boot.  If I disabled the
calculation, the crash didn't occur.  There also seemed to be a timing
dependency affecting the crash.  I finally realized that the
flush_tlb_all() timing test runs just after the secondary CPUs are
started.  There seems to be a problem with running flush_tlb_all() too
soon after the CPUs are started.

The timing for the range test always seemed okay.  So, I reversed the
order of the two timing tests and I haven't had a crash at this point so
far.

I added a couple of information messages which I have left to help with
diagnosis if the problem should appear on another machine.

This version reduces the minimum TLB flush threshold to 16 KiB.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>

1 files changed, 10 insertions, 8 deletions

diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index bddd2acebdcc..9f1c29d06574 100644
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -364,7 +364,7 @@ EXPORT_SYMBOL(flush_kernel_icache_range_asm);
 #define FLUSH_THRESHOLD 0x80000 /* 0.5MB */
 static unsigned long parisc_cache_flush_threshold __read_mostly = FLUSH_THRESHOLD;
 
-#define FLUSH_TLB_THRESHOLD (2*1024*1024) /* 2MB initial TLB threshold */
+#define FLUSH_TLB_THRESHOLD (16*1024) /* 16 KiB minimum TLB threshold */
 static unsigned long parisc_tlb_flush_threshold __read_mostly = FLUSH_TLB_THRESHOLD;
 
 void __init parisc_setup_cache_timing(void)
@@ -404,10 +404,6 @@ void __init parisc_setup_cache_timing(void)
                 goto set_tlb_threshold;
         }
 
-        alltime = mfctl(16);
-        flush_tlb_all();
-        alltime = mfctl(16) - alltime;
-
         size = 0;
         start = (unsigned long) _text;
         rangetime = mfctl(16);
@@ -418,13 +414,19 @@ void __init parisc_setup_cache_timing(void)
         }
         rangetime = mfctl(16) - rangetime;
 
-        printk(KERN_DEBUG "Whole TLB flush %lu cycles, flushing %lu bytes %lu cycles\n",
+        alltime = mfctl(16);
+        flush_tlb_all();
+        alltime = mfctl(16) - alltime;
+
+        printk(KERN_INFO "Whole TLB flush %lu cycles, Range flush %lu bytes %lu cycles\n",
                 alltime, size, rangetime);
 
-        threshold = PAGE_ALIGN(num_online_cpus() * size * alltime / rangetime);
+        threshold = PAGE_ALIGN((num_online_cpus() * size * alltime) / rangetime);
+        printk(KERN_INFO "Calculated TLB flush threshold %lu KiB\n",
+                threshold/1024);
 
 set_tlb_threshold:
-        if (threshold)
+        if (threshold > parisc_tlb_flush_threshold)
                 parisc_tlb_flush_threshold = threshold;
         printk(KERN_INFO "TLB flush threshold set to %lu KiB\n",
                 parisc_tlb_flush_threshold/1024);