[coreboot] [PATCH] Streamline CPU_ADDR_BITS usage

Warren Turkal wt at penguintechs.org
Mon Oct 4 07:58:30 CEST 2010

Are there processors where that CPU_ADDR_BITS_MASK cannot be reliably
retrieved from CPUID? What is the harm in using a value that is too
small for the CAR setup? In other words could we use the least common
value for any CPU instead of having a different setting on each
different chip?


On Sun, Oct 3, 2010 at 5:14 PM, Scott Duplichan <scott at notabs.org> wrote:
> ]
> ]But note that the current form is also a bit dangerous. It hardcodes 40bits
> ]for K8 and 48bits for Fam10h here unconditionally. I don't know if this
> ]assumption is always correct for all CPUs. Using the correct per-CPU
> ]CONFIG_CPU_ADDR_BITS_MASK would definately be safer (if this mechanism
> ]can work here at all). Are we sure there are no K8 systems that support
> ]CPUs with bits != 40? Are we sure there are no Fam10h CPUs with
> ]bits != 48 (and that there never will be in the future)?
> Getting this info from cpuid is the way to go (It is reliable on AMD
> systems). Hard-coding is next best. It is fixed per family:
> 0Fh 40
> 10h 48
> 11h 40
> 12h 40
> 13h (no product)
> 14h 36
> 15h 48
> Hopefully AMD will start supplying coreboot-ready support code, which
> will allow coreboot to run exactly the same reference code as every
> other AMD BIOS.
> Thanks,
> Scott
> ]Uwe.
> ]--
> ]http://hermann-uwe.de     | http://sigrok.org
> ]http://randomprojects.org | http://unmaintained-free-software.org
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