diff options
| -rw-r--r-- | chipset_enable.c | 78 |
1 files changed, 52 insertions, 26 deletions
diff --git a/chipset_enable.c b/chipset_enable.c index 2ec4c7dc..c9b09980 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; } |