Attached is a patch that enables AMD Geode CS5536 chipset support. I
have tested it successfully on a MSM800 board from digital logic. It
does, however, have a few issues that I would like some feedback on.
In my discussions with Marc Jones, Geode systems write protect the BIOS
via RCONFs (cache settings similar to MTRRs). Unlocking requires
changing MSR 0x1808 top byte to 0x22. Reading and writing to the msr,
however, requires instrucitons rdmsr/wrmsr, which are ring0 privileged
instructions so only the kernel can do the read/write. So my patch uses
the msr kernel module to access these instructions from user space using
the /dev/cpu/0/msr device.
My questions are:
- I do not think this is portable beyond linux. Is that an issue?
- My code assumes the msr kernel module is already loaded. Is there a
way to force a kernel module to load from the C code? My code does die
gracefully with a message reminding them to load the kernel module if
things fail.
- It seems like there should be a way to revert the msr back after
flashing is completed to put the bios back in write protect mode. Is
there a cleanup mechanism available? Something like disable_flash...
Thanks,
Lane Brooks
Index: chipset_enable.c
===================================================================
--- chipset_enable.c (revision 2816)
+++ chipset_enable.c (working copy)
@@ -23,9 +23,14 @@
* Contains the chipset specific flash enables.
*/
+#define _LARGEFILE64_SOURCE
#include <stdio.h>
#include <pci/pci.h>
#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
#include "flash.h"
static int enable_flash_ali_m1533(struct pci_dev *dev, char *name)
@@ -218,6 +223,55 @@
return 0;
}
+static int enable_flash_cs5536(struct pci_dev *dev, char *name)
+{
+ int fd_msr;
+ unsigned char buf[8];
+ unsigned long 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 instrucitons 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
+ *
+ * I do not think this is portable beyond linux (lane).
+ * It seems like there should also be a function that locks the
+ * flash back up after it is done.
+ */
+
+ fd_msr = open("/dev/cpu/0/msr", O_RDONLY);
+ if (!fd_msr) {
+ perror("open msr");
+ return -1;
+ }
+ lseek64(fd_msr, (off64_t) addr, SEEK_SET);
+ read(fd_msr, buf, 8);
+ close(fd_msr);
+
+ if (buf[7] != 0x22) {
+ printf("Enabling Geode MSR to write to flash.\n");
+ buf[7] = 0x22;
+ fd_msr = open("/dev/cpu/0/msr", O_WRONLY);
+ if (!fd_msr) {
+ perror("open msr");
+ return -1;
+ }
+ 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");
+ return -1;
+ }
+ close(fd_msr);
+ }
+ return 0;
+}
+
static int enable_flash_sc1100(struct pci_dev *dev, char *name)
{
uint8_t new;
@@ -459,6 +513,7 @@
{0x1078, 0x0100, "CS5530/CS5530A", enable_flash_cs5530},
{0x100b, 0x0510, "SC1100", enable_flash_sc1100},
{0x1039, 0x0008, "SIS5595", enable_flash_sis5595},
+ {0x1022, 0x2080, "AMD GEODE CS5536", enable_flash_cs5536},
{0x1022, 0x7468, "AMD8111", enable_flash_amd8111},
{0x10B9, 0x1533, "ALi M1533", enable_flash_ali_m1533},
/* this fallthrough looks broken. */
--
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