Messages in this thread | | | Date | Tue, 10 Aug 2004 19:59:06 +0800 | From | Michael Clark <> | Subject | Re: [PATCH] - Initial dothan speedstep support |
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Hi Dave, Jeremy,
I thought i'd give the ACPI code in speedstep-centrino a try as I wanted to see what the BIOS freq/voltage tables the vendor was using due to the apparent choice of voltages (VID#A through VID#C) in the processor specs.
Anyway this is what I found (with the debug code in attached patch):
centrino_cpu_init_acpi: 1800000000 Hz, 1340e-03 volts centrino_cpu_init_acpi: 1600000000 Hz, 1292e-03 volts centrino_cpu_init_acpi: 1400000000 Hz, 1228e-03 volts centrino_cpu_init_acpi: 1200000000 Hz, 1164e-03 volts centrino_cpu_init_acpi: 1000000000 Hz, 1116e-03 volts centrino_cpu_init_acpi: 800000000 Hz, 1052e-03 volts centrino_cpu_init_acpi: 600000000 Hz, 988e-03 volts
It appears the T42 is using the VID#A voltages (the highest) and my patch was using VID#C (the 2nd from lowest) for which the upper voltage has the biggest difference being 0.032 volts lower - not much in it.
As I said earlier in my reading of the specs there seemed to be no guidance on which profile to use aside from the voltage and ripple tolerance tables.
So the attached patch (in addition to ACPI freq table debug message) changes the table version to use the VID#A voltage so as to err on the conservative side of a higher voltage (as the upper voltage max for the chip is 1.6v) to allow for cases where the error on the voltage would drop it too low - not sure if just IBM are using this. Would be interesting to see the ACPI freq/voltage tables for other vendor's Dothan laptops.
Not sure on whether we should do this although it means we match at least what one vendor has done? Any ideas? (debug printk may be useful for those with ACPI and speedstep for debugging incorrect BIOS tables).
Thanks ~mc [unhandled content-type:application/octect-stream] | |