On recent u-boots, the watchdog is turned on / left enabled. The
Beaglebone Black rev. C ships with such a u-boot internally so any OS
booting from it must disable the watchdog or the user is required to
change the stock uboot.
From 4132f23920c743ec2dca0ffd63f8dcf833eb0a1b Mon Sep 17 00:00:00 2001
From: Ben Gras <b...@rtems.org>
Date: Thu, 4 Dec 2014 18:21:11 +0100
Subject: [PATCH] beagle bsp: disable watchdog on am335x
On recent u-boots, the watchdog is turned on / left enabled. The
Beaglebone Black rev. C ships with such a u-boot internally so any
application booting from it must disable the watchdog.
Therefore this change is needed to boot an RTEMS app out-of-the-box
on a BBB Rev C - otherwise the user button must be held during boot
(to bypass the stock uboot) or the internal uboot must be updated. To
allow for a better out-of-the-box experience, we just turn off the
watchdog.
---
c/src/lib/libbsp/arm/beagle/clock.c | 9 +++++++++
c/src/lib/libcpu/arm/shared/include/am335x.h | 6 ++++++
2 files changed, 15 insertions(+)
diff --git a/c/src/lib/libbsp/arm/beagle/clock.c b/c/src/lib/libbsp/arm/beagle/clock.c
index 13c0607..b2582d1 100644
--- a/c/src/lib/libbsp/arm/beagle/clock.c
+++ b/c/src/lib/libbsp/arm/beagle/clock.c
@@ -251,6 +251,15 @@ beagle_clock_initialize(void)
OMAP3_TCLR_OVF_TRG | OMAP3_TCLR_AR | OMAP3_TCLR_ST);
/* also initilize the free runnning timer */
omap3_frclock_init();
+
+#if IS_AM335X
+ /* Disable AM335X watchdog */
+ mmio_write(AM335X_WDT_BASE+AM335X_WDT_WSPR, 0xAAAA);
+ while(mmio_read(AM335X_WDT_BASE+AM335X_WDT_WWPS) != 0) ;
+ mmio_write(AM335X_WDT_BASE+AM335X_WDT_WSPR, 0x5555);
+ while(mmio_read(AM335X_WDT_BASE+AM335X_WDT_WWPS) != 0) ;
+#endif
+
}
static void beagle_clock_at_tick(void)
diff --git a/c/src/lib/libcpu/arm/shared/include/am335x.h b/c/src/lib/libcpu/arm/shared/include/am335x.h
index 4b5ea73..265cc36 100644
--- a/c/src/lib/libcpu/arm/shared/include/am335x.h
+++ b/c/src/lib/libcpu/arm/shared/include/am335x.h
@@ -274,3 +274,9 @@
/* Control posted mode and functional SW reset */
#define AM335X_TIMER_TCAR2 0x058
/* Second captured value of counter register */
+#define AM335X_WDT_BASE 0x44E35000
+ /* Watchdog timer */
+#define AM335X_WDT_WWPS 0x34
+ /* Command posted status */
+#define AM335X_WDT_WSPR 0x48
+ /* Activate/deactivate sequence */
--
1.9.1
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