lwmon5 watchdog: limit trigger rate

Limit the rate of h/w watch-dog triggering on the LWMON5 board by
the CONFIG_WD_MAX_RATE value.

Note that an earlier version of this patch which used microseconds
instead of ticks dis not work. The problem was that we used
usec2ticks() to convert microseconds into ticks. usec2ticks() uses
get_tbclk(), which in turn calls get_sys_info(). It turns out that
this function does a lot of prolonged operations (like divisions)
which take too much time so we do not trigger the watchdog in time,
and it resets the system.

Signed-off-by: Yuri Tikhonov <yur@emcraft.com>

diff --git a/board/lwmon5/lwmon5.c b/board/lwmon5/lwmon5.c
index e5fa25937b5e069eeff81cbdaa33471e99627e92..b63fbdc0cdd5e59e3a77ea832cd02fae9d91026b 100644 (file)
--- a/board/lwmon5/lwmon5.c
+++ b/board/lwmon5/lwmon5.c
@@ -476,6 +476,24 @@ int is_pci_host(struct pci_controller *hose)
 void hw_watchdog_reset(void)
 {
        int val;
+#if defined(CONFIG_WD_MAX_RATE)
+       unsigned long long ct = get_ticks();
+
+       /*
+        * Don't allow watch-dog triggering more frequently than
+        * the predefined value CONFIG_WD_MAX_RATE [ticks].
+        */
+       if (ct >= gd->wdt_last) {
+               if ((ct - gd->wdt_last) < CONFIG_WD_MAX_RATE)
+                       return;
+       } else {
+               /* Time base counter had been reset */
+               if (((unsigned long long)(-1) - gd->wdt_last + ct) <
+                   CONFIG_WD_MAX_RATE)
+                       return;
+       }
+       gd->wdt_last = get_ticks();
+#endif
 
        /*
         * Toggle watchdog output

diff --git a/include/asm-ppc/global_data.h b/include/asm-ppc/global_data.h
index e07092baa4d8573d77c4f04208850cdef7cabf95..46576046a4c9350d67ead1a05d430e7fff27b7cb 100644 (file)
--- a/include/asm-ppc/global_data.h
+++ b/include/asm-ppc/global_data.h
@@ -154,6 +154,9 @@ typedef     struct  global_data {
 #endif
 #if defined(CONFIG_LWMON) || defined(CONFIG_LWMON5)
        unsigned long kbd_status;
+#endif
+#if defined(CONFIG_WD_MAX_RATE)
+       unsigned long long wdt_last;    /* trace watch-dog triggering rate */
 #endif
        void            **jt;           /* jump table */
 } gd_t;

diff --git a/include/configs/lwmon5.h b/include/configs/lwmon5.h
index ced7ba6f05cf3bf05e3fb09d09685811ba562068..58f078b6d89c6d087dacaa0bc188ef60be50b58d 100644 (file)
--- a/include/configs/lwmon5.h
+++ b/include/configs/lwmon5.h
@@ -455,6 +455,7 @@
 
 #define CONFIG_HW_WATCHDOG     1       /* Use external HW-Watchdog     */
 #define CONFIG_WD_PERIOD       40000   /* in usec */
+#define CONFIG_WD_MAX_RATE     66600   /* in ticks */
 
 /*
  * For booting Linux, the board info and command line data