Improve error handling and make RCONF_DEFAULT_MSR address be a constant

Also, move a big code comment to the top of enable_flash_cs5536().

Corresponding to flashrom svn r193 and coreboot v2 svn r3098.

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

1 files changed, 52 insertions, 26 deletions

diff --git a/chipset_enable.c b/chipset_enable.c
index 2ec4c7dcc..c9b09980c 100644
--- a/chipset_enable.c
+++ b/chipset_enable.c
@@ -226,71 +226,97 @@ static int enable_flash_cs5530(struct pci_dev *dev, const char *name)
 	return 0;
 }
 
+/**
+ * Geode systems write protect the BIOS via RCONFs (cache settings similar
+ * to MTRRs). To unlock, change MSR 0x1808 top byte to 0x22. Reading and
+ * writing to MSRs, however requires instructions rdmsr/wrmsr, which are
+ * ring0 privileged instructions so only the kernel can do the read/write.
+ * This function, therefore, requires that the msr kernel module be loaded
+ * to access these instructions from user space using device /dev/cpu/0/msr.
+ *
+ * This hard-coded location 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.
+ */
 static int enable_flash_cs5536(struct pci_dev *dev, const char *name)
 {
-	#define MSR_NORF_CTL	0x51400018
+	#define MSR_RCONF_DEFAULT	0x1808
+	#define MSR_NORF_CTL		0x51400018
 
 	int fd_msr;
 	unsigned char buf[8];
-	unsigned int addr = 0x1808;
-
-	/* Geode systems write protect the BIOS via RCONFs (cache
-	 * settings similar to MTRRs). To unlock, change MSR 0x1808
-	 * top byte to 0x22. Reading and writing to msr, however
-	 * requires instructions rdmsr/wrmsr, which are ring0 privileged
-	 * instructions so only the kernel can do the read/write.  This
-	 * function, therefore, requires that the msr kernel module be
-	 * loaded to access these instructions from user space using
-	 * device /dev/cpu/0/msr.  This hard-coded driver location
-	 * 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_RDWR);
 	if (!fd_msr) {
 		perror("open msr");
 		return -1;
 	}
-	lseek64(fd_msr, (off64_t) addr, SEEK_SET);
-	read(fd_msr, buf, 8);
+
+	if (lseek64(fd_msr, (off64_t) MSR_RCONF_DEFAULT, SEEK_SET) == -1) {
+		perror("lseek64");
+		close(fd_msr);
+		return -1;
+	}
+
+	if (read(fd_msr, buf, 8) != 8) {
+		perror("read");
+		close(fd_msr);
+		return -1;
+	}
 
 	printf("Enabling Geode MSR to write to flash.\n");
 
 	if (buf[7] != 0x22) {
 		buf[7] &= 0xfb;
-		lseek64(fd_msr, (off64_t) addr, SEEK_SET);
+		if (lseek64(fd_msr, (off64_t) MSR_RCONF_DEFAULT, SEEK_SET) == -1) {
+			perror("lseek64");
+			close(fd_msr);
+			return -1;
+		}
+
 		if (write(fd_msr, buf, 8) < 0) {
 			perror("msr write");
 			printf("Cannot write to MSR. Did you run 'modprobe msr'?\n");
+			close(fd_msr);
 			return -1;
 		}
 	}
 
-	lseek64(fd_msr, (off64_t) MSR_NORF_CTL, SEEK_SET);
+	if (lseek64(fd_msr, (off64_t) MSR_NORF_CTL, SEEK_SET) == -1) {
+		perror("lseek64");
+		close(fd_msr);
+		return -1;
+	}
+
 	if (read(fd_msr, buf, 8) != 8) {
 		perror("read msr");
+		close(fd_msr);
 		return -1;
 	}
 
 	/* Raise WE_CS3 bit. */
 	buf[0] |= 0x08;
 
-	lseek64(fd_msr, (off64_t) MSR_NORF_CTL, SEEK_SET);
+	if (lseek64(fd_msr, (off64_t) MSR_NORF_CTL, SEEK_SET) == -1) {
+		perror("lseek64");
+		close(fd_msr);
+		return -1;
+	}
 	if (write(fd_msr, buf, 8) < 0) {
 		perror("msr write");
 		printf("Cannot write to MSR. Did you run 'modprobe msr'?\n");
+		close(fd_msr);
 		return -1;
 	}
 
 	close(fd_msr);
 
+	#undef MSR_RCONF_DEFAULT
 	#undef MSR_NORF_CTL
 	return 0;
 }