Write enable flash chips attached to CS3 of CS5536 chipsets (AMD Geode)

This implements support for devices using AMD Geode companion chip
CS5536 that have the Boot ROM on NOR flash that is directly connected to
FLASH_CS3 (Boot Flash Chip Select). We need to write enable it in the
NORF_CTL MSR register for flashrom to be able to write to it, including
JEDEC probe commands.

This patch allows us to stop using AMD gx_utils.ko for BIOS flashing on
the DBE61.

Corresponding to flashrom svn r192 and coreboot v2 svn r3097.

Signed-off-by: Mart Raudsepp <mart.raudsepp@artecdesign.ee>
Acked-by: Uwe Hermann <uwe@hermann-uwe.de>

1 files changed, 33 insertions, 12 deletions

diff --git a/chipset_enable.c b/chipset_enable.c
index 4cbb94178..2ec4c7dcc 100644
--- a/chipset_enable.c
+++ b/chipset_enable.c
@@ -228,6 +228,8 @@ static int enable_flash_cs5530(struct pci_dev *dev, const char *name)
 
 static int enable_flash_cs5536(struct pci_dev *dev, const char *name)
 {
+	#define MSR_NORF_CTL	0x51400018
+
 	int fd_msr;
 	unsigned char buf[8];
 	unsigned int addr = 0x1808;
@@ -243,34 +245,53 @@ static int enable_flash_cs5536(struct pci_dev *dev, const char *name)
 	 * could have potential problems on SMP machines since it
 	 * assumes cpu0, but it is safe on the Geode which is not SMP.
 	 *
+	 * Geode systems also write protect the NOR flash chip itself
+	 * via MSR_NORF_CTL. To enable write to NOR Boot flash for the
+	 * benefit of systems that have such a setup, raise
+	 * MSR 0x51400018 WE_CS3 (write enable Boot Flash Chip Select).
+	 *
 	 * This is probably not portable beyond Linux.
 	 */
 
-	fd_msr = open("/dev/cpu/0/msr", O_RDONLY);
+	fd_msr = open("/dev/cpu/0/msr", O_RDWR);
 	if (!fd_msr) {
 		perror("open msr");
 		return -1;
 	}
 	lseek64(fd_msr, (off64_t) addr, SEEK_SET);
 	read(fd_msr, buf, 8);
-	close(fd_msr);
+
+	printf("Enabling Geode MSR to write to flash.\n");
+
 	if (buf[7] != 0x22) {
-		printf("Enabling Geode MSR to write to flash.\n");
-		buf[7] &= 0xFB;
-		fd_msr = open("/dev/cpu/0/msr", O_WRONLY);
-		if (!fd_msr) {
-			perror("open msr");
-			return -1;
-		}
+		buf[7] &= 0xfb;
 		lseek64(fd_msr, (off64_t) addr, SEEK_SET);
 		if (write(fd_msr, buf, 8) < 0) {
 			perror("msr write");
-			printf
-			    ("Cannot write to MSR.  Make sure msr kernel is loaded: 'modprobe msr'\n");
+			printf("Cannot write to MSR. Did you run 'modprobe msr'?\n");
 			return -1;
 		}
-		close(fd_msr);
 	}
+
+	lseek64(fd_msr, (off64_t) MSR_NORF_CTL, SEEK_SET);
+	if (read(fd_msr, buf, 8) != 8) {
+		perror("read msr");
+		return -1;
+	}
+
+	/* Raise WE_CS3 bit. */
+	buf[0] |= 0x08;
+
+	lseek64(fd_msr, (off64_t) MSR_NORF_CTL, SEEK_SET);
+	if (write(fd_msr, buf, 8) < 0) {
+		perror("msr write");
+		printf("Cannot write to MSR. Did you run 'modprobe msr'?\n");
+		return -1;
+	}
+
+	close(fd_msr);
+
+	#undef MSR_NORF_CTL
 	return 0;
 }