Improve error handling and make RCONF_DEFAULT_MSR address be a constant.

[coreboot.git] / util / flashrom / chipset_enable.c

diff --git a/util/flashrom/chipset_enable.c b/util/flashrom/chipset_enable.c
index 2ec4c7dcc761d4f1868d08ee94683b8d408ff709..c9b09980c4a41d6445b291acdb6b0d7c11daa9a5 100644 (file)
--- a/util/flashrom/chipset_enable.c
+++ b/util/flashrom/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;
 }