Similarly to memory errors in ECC systems also rate-limit memory parity 
errors for KN02-BA, KN02-CA, KN04-BA, KN04-CA DECstation and DECsystem 
models.  Unlike with ECC these events are always fatal and are less 
likely to cause a message flood, but handle them the same way for 
consistency.

Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
---
 arch/mips/dec/kn02xa-berr.c |   26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

linux-mips-dec-berr-ratelimit-kn02xa.diff
Index: linux-macro/arch/mips/dec/kn02xa-berr.c
===================================================================
--- linux-macro.orig/arch/mips/dec/kn02xa-berr.c
+++ linux-macro/arch/mips/dec/kn02xa-berr.c
@@ -6,12 +6,13 @@
  *	DECstation/DECsystem 5000/20, /25, /33 (KN02-CA), 5000/50
  *	(KN04-CA) systems.
  *
- *	Copyright (c) 2005  Maciej W. Rozycki
+ *	Copyright (c) 2005, 2026  Maciej W. Rozycki
  */
 
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
+#include <linux/ratelimit.h>
 #include <linux/types.h>
 
 #include <asm/addrspace.h>
@@ -50,6 +51,10 @@ static int dec_kn02xa_be_backend(struct
 	static const char paritystr[] = "parity error";
 	static const char lanestat[][4] = { " OK", "BAD" };
 
+	static DEFINE_RATELIMIT_STATE(rs,
+				      DEFAULT_RATELIMIT_INTERVAL,
+				      DEFAULT_RATELIMIT_BURST);
+
 	const char *kind, *agent, *cycle, *event;
 	unsigned long address;
 
@@ -79,18 +84,19 @@ static int dec_kn02xa_be_backend(struct
 	if (is_fixup)
 		action = MIPS_BE_FIXUP;
 
-	if (action != MIPS_BE_FIXUP)
+	if (action != MIPS_BE_FIXUP && __ratelimit(&rs)) {
 		printk(KERN_ALERT "Bus error %s: %s %s %s at %#010lx\n",
 			kind, agent, cycle, event, address);
 
-	if (action != MIPS_BE_FIXUP && address < 0x10000000)
-		printk(KERN_ALERT "  Byte lane status %#3x -- "
-		       "#3: %s, #2: %s, #1: %s, #0: %s\n",
-		       (mer & KN02XA_MER_BYTERR) >> 8,
-		       lanestat[(mer & KN02XA_MER_BYTERR_3) != 0],
-		       lanestat[(mer & KN02XA_MER_BYTERR_2) != 0],
-		       lanestat[(mer & KN02XA_MER_BYTERR_1) != 0],
-		       lanestat[(mer & KN02XA_MER_BYTERR_0) != 0]);
+		if (address < 0x10000000)
+			printk(KERN_ALERT "  Byte lane status %#3x -- "
+			       "#3: %s, #2: %s, #1: %s, #0: %s\n",
+			       (mer & KN02XA_MER_BYTERR) >> 8,
+			       lanestat[(mer & KN02XA_MER_BYTERR_3) != 0],
+			       lanestat[(mer & KN02XA_MER_BYTERR_2) != 0],
+			       lanestat[(mer & KN02XA_MER_BYTERR_1) != 0],
+			       lanestat[(mer & KN02XA_MER_BYTERR_0) != 0]);
+	}
 
 	return action;
 }