mainboard/kgpe-d16|kcma-d8: Update memory test to include second PRNG stage

The existing memory test routine was insufficient to detect certain types
of bus instability related to multiple incompatible RDIMMs on one channel.

Add a PRNG second stage test to the memory test routine.  This second stage
test reliably detects faults in memory setup for RDIMM configurations that
also fail under the proprietary BIOS.

Change-Id: I44721447ce4c2b728d4a8f328ad1a3eb8f324d3d
Signed-off-by: Timothy Pearson <tpearson@raptorengineeringinc.com>
Reviewed-on: https://review.coreboot.org/14502
Tested-by: build bot (Jenkins)
Tested-by: Raptor Engineering Automated Test Stand <noreply@raptorengineeringinc.com>
Reviewed-by: Martin Roth <martinroth@google.com>

1 files changed, 55 insertions, 7 deletions

diff --git a/src/mainboard/asus/kgpe-d16/romstage.c b/src/mainboard/asus/kgpe-d16/romstage.c
index e6bd91cbe0..5a7400e190 100644
--- a/src/mainboard/asus/kgpe-d16/romstage.c
+++ b/src/mainboard/asus/kgpe-d16/romstage.c
@@ -1,7 +1,7 @@
 /*
  * This file is part of the coreboot project.
  *
- * Copyright (C) 2015 Timothy Pearson <tpearson@raptorengineeringinc.com>, Raptor Engineering
+ * Copyright (C) 2015 - 2016 Raptor Engineering, LLC
  *
  * Copyright (C) 2007 AMD
  * Written by Yinghai Lu <yinghailu@amd.com> for AMD.
@@ -287,28 +287,76 @@ static void execute_memory_test(void)
 {
 	/* Test DRAM functionality */
 	uint32_t i;
+	uint32_t v;
+	uint32_t w;
+	uint32_t x;
+	uint32_t y;
+	uint32_t z;
 	uint32_t* dataptr;
-	printk(BIOS_DEBUG, "Writing test patterns to memory...\n");
+	uint32_t readback;
+	uint32_t start = 0x300000;
+	printk(BIOS_DEBUG, "Writing test pattern 1 to memory...\n");
 	for (i=0; i < 0x1000000; i = i + 8) {
-		dataptr = (void *)(0x300000 + i);
+		dataptr = (void *)(start + i);
 		*dataptr = 0x55555555;
-		dataptr = (void *)(0x300000 + i + 4);
+		dataptr = (void *)(start + i + 4);
 		*dataptr = 0xaaaaaaaa;
 	}
 	printk(BIOS_DEBUG, "Done!\n");
 	printk(BIOS_DEBUG, "Testing memory...\n");
-	uint32_t readback;
 	for (i=0; i < 0x1000000; i = i + 8) {
-		dataptr = (void *)(0x300000 + i);
+		dataptr = (void *)(start + i);
 		readback = *dataptr;
 		if (readback != 0x55555555)
 			printk(BIOS_DEBUG, "%p: INCORRECT VALUE %08x (should have been %08x)\n", dataptr, readback, 0x55555555);
-		dataptr = (void *)(0x300000 + i + 4);
+		dataptr = (void *)(start + i + 4);
 		readback = *dataptr;
 		if (readback != 0xaaaaaaaa)
 			printk(BIOS_DEBUG, "%p: INCORRECT VALUE %08x (should have been %08x)\n", dataptr, readback, 0xaaaaaaaa);
 	}
 	printk(BIOS_DEBUG, "Done!\n");
+	printk(BIOS_DEBUG, "Writing test pattern 2 to memory...\n");
+	/* Set up the PRNG seeds for initial write */
+	w = 0x55555555;
+	x = 0xaaaaaaaa;
+	y = 0x12345678;
+	z = 0x87654321;
+	for (i=0; i < 0x1000000; i = i + 4) {
+		/* Use Xorshift as a PRNG to stress test the bus */
+		v = x;
+		v ^= v << 11;
+		v ^= v >> 8;
+		x = y;
+		y = z;
+		z = w;
+		w ^= w >> 19;
+		w ^= v;
+		dataptr = (void *)(start + i);
+		*dataptr = w;
+	}
+	printk(BIOS_DEBUG, "Done!\n");
+	printk(BIOS_DEBUG, "Testing memory...\n");
+	/* Reset the PRNG seeds for readback */
+	w = 0x55555555;
+	x = 0xaaaaaaaa;
+	y = 0x12345678;
+	z = 0x87654321;
+	for (i=0; i < 0x1000000; i = i + 4) {
+		/* Use Xorshift as a PRNG to stress test the bus */
+		v = x;
+		v ^= v << 11;
+		v ^= v >> 8;
+		x = y;
+		y = z;
+		z = w;
+		w ^= w >> 19;
+		w ^= v;
+		dataptr = (void *)(start + i);
+		readback = *dataptr;
+		if (readback != w)
+			printk(BIOS_DEBUG, "%p: INCORRECT VALUE %08x (should have been %08x)\n", dataptr, readback, w);
+	}
+	printk(BIOS_DEBUG, "Done!\n");
 }
 #endif