[LinuxBIOS] flashrom support for AMD Geode CS5536
jordan.crouse at amd.com
Tue Oct 2 18:34:38 CEST 2007
On 02/10/07 10:20 -0600, Lane Brooks wrote:
> 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?
Right now, no. Any other *nixish OS will have to solve the MSR problem
for themselves. If they chose something different, then we'll cross that
bridge when we get to it.
> - 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.
Thats the best we can do, without getting more non-portable. I think.
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