3 files changed, 33 insertions, 9 deletions

diff --git a/arch/arm/mach-ixp2000/core.c b/arch/arm/mach-ixp2000/core.c
index 4f3c3d5c781c..fc0555596d6d 100644
--- a/arch/arm/mach-ixp2000/core.c
+++ b/arch/arm/mach-ixp2000/core.c
@@ -162,12 +162,13 @@ void __init ixp2000_map_io(void)
 static unsigned ticks_per_jiffy;
 static unsigned ticks_per_usec;
 static unsigned next_jiffy_time;
+static volatile unsigned long *missing_jiffy_timer_csr;
 
 unsigned long ixp2000_gettimeoffset (void)
 {
         unsigned long offset;
 
-        offset = next_jiffy_time - *IXP2000_T4_CSR;
+        offset = next_jiffy_time - *missing_jiffy_timer_csr;
 
         return offset / ticks_per_usec;
 }
@@ -179,7 +180,7 @@ static int ixp2000_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
         /* clear timer 1 */
         ixp2000_reg_write(IXP2000_T1_CLR, 1);
         
-        while ((next_jiffy_time - *IXP2000_T4_CSR) > ticks_per_jiffy) {
+        while ((next_jiffy_time - *missing_jiffy_timer_csr) > ticks_per_jiffy) {
                 timer_tick(regs);
                 next_jiffy_time -= ticks_per_jiffy;
         }
@@ -197,20 +198,37 @@ static struct irqaction ixp2000_timer_irq = {
 
 void __init ixp2000_init_time(unsigned long tick_rate)
 {
-        ixp2000_reg_write(IXP2000_T1_CLR, 0);
-        ixp2000_reg_write(IXP2000_T4_CLR, 0);
-
         ticks_per_jiffy = (tick_rate + HZ/2) / HZ;
         ticks_per_usec = tick_rate / 1000000;
 
+        /*
+         * We use timer 1 as our timer interrupt.
+         */
+        ixp2000_reg_write(IXP2000_T1_CLR, 0);
         ixp2000_reg_write(IXP2000_T1_CLD, ticks_per_jiffy - 1);
         ixp2000_reg_write(IXP2000_T1_CTL, (1 << 7));
 
         /*
-         * We use T4 as a monotonic counter to track missed jiffies
+         * We use a second timer as a monotonic counter for tracking
+         * missed jiffies.  The IXP2000 has four timers, but if we're
+         * on an A-step IXP2800, timer 2 and 3 don't work, so on those
+         * chips we use timer 4.  Timer 4 is the only timer that can
+         * be used for the watchdog, so we use timer 2 if we're on a
+         * non-buggy chip.
          */
-        ixp2000_reg_write(IXP2000_T4_CLD, -1);
-        ixp2000_reg_write(IXP2000_T4_CTL, (1 << 7));
+        if ((*IXP2000_PRODUCT_ID & 0x001ffef0) == 0x00000000) {
+                printk(KERN_INFO "Enabling IXP2800 erratum #25 workaround\n");
+
+                ixp2000_reg_write(IXP2000_T4_CLR, 0);
+                ixp2000_reg_write(IXP2000_T4_CLD, -1);
+                ixp2000_reg_write(IXP2000_T4_CTL, (1 << 7));
+                missing_jiffy_timer_csr = IXP2000_T4_CSR;
+        } else {
+                ixp2000_reg_write(IXP2000_T2_CLR, 0);
+                ixp2000_reg_write(IXP2000_T2_CLD, -1);
+                ixp2000_reg_write(IXP2000_T2_CTL, (1 << 7));
+                missing_jiffy_timer_csr = IXP2000_T2_CSR;
+        }
         next_jiffy_time = 0xffffffff;
 
         /* register for interrupt */
diff --git a/drivers/char/watchdog/ixp2000_wdt.c b/drivers/char/watchdog/ixp2000_wdt.c
index ab659d37b4d2..4e98c215e5b1 100644
--- a/drivers/char/watchdog/ixp2000_wdt.c
+++ b/drivers/char/watchdog/ixp2000_wdt.c
@@ -192,7 +192,12 @@ static struct miscdevice ixp2000_wdt_miscdev =
 
 static int __init ixp2000_wdt_init(void)
 {
-        wdt_tick_rate = (*IXP2000_T1_CLD * HZ)/ 256;;
+        if ((*IXP2000_PRODUCT_ID & 0x001ffef0) == 0x00000000) {
+                printk(KERN_INFO "Unable to use IXP2000 watchdog due to IXP2800 erratum #25.\n");
+                return -EIO;
+        }
+
+        wdt_tick_rate = (*IXP2000_T1_CLD * HZ) / 256;
 
         return misc_register(&ixp2000_wdt_miscdev);
 }
diff --git a/include/asm-arm/arch-ixp2000/ixp2000-regs.h b/include/asm-arm/arch-ixp2000/ixp2000-regs.h
index 6c56708d0ff0..a1d9e181b10f 100644
--- a/include/asm-arm/arch-ixp2000/ixp2000-regs.h
+++ b/include/asm-arm/arch-ixp2000/ixp2000-regs.h
@@ -363,6 +363,7 @@
 #define IXP2000_MIN_REV_MASK            0x0000000F
 #define IXP2000_PROD_ID_MASK            0xFFFFFFFF
 
+#define IXP2000_PRODUCT_ID              GLOBAL_REG(0x00)
 #define IXP2000_MISC_CONTROL            GLOBAL_REG(0x04)
 #define IXP2000_MSF_CLK_CNTRL           GLOBAL_REG(0x08)
 #define IXP2000_RESET0                  GLOBAL_REG(0x0c)