Re: [PATCH] powernow-k8: depend on acpi-processor for SMP systems

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Pavel Machek wrote:
Hi!

powernow-k8 uses PSB BIOS tables to read frequency info on UP systems, but
on SMP it requires the acpi-processor driver. Kconfig should be updated
accordingly to avoid the issues that users are running into.

http://bugzilla.kernel.org/show_bug.cgi?id=8075
https://bugs.gentoo.org/show_bug.cgi?id=178585

Signed-off-by: Daniel Drake <[email protected]>

Index: linux/arch/i386/kernel/cpu/cpufreq/Kconfig
===================================================================
--- linux.orig/arch/i386/kernel/cpu/cpufreq/Kconfig
+++ linux/arch/i386/kernel/cpu/cpufreq/Kconfig
@@ -81,6 +81,7 @@ config X86_POWERNOW_K7_ACPI
 config X86_POWERNOW_K8
 	tristate "AMD Opteron/Athlon64 PowerNow!"
 	select CPU_FREQ_TABLE
+	select ACPI_PROCESSOR if SMP
 	depends on EXPERIMENTAL
 	help
 	  This adds the CPUFreq driver for mobile AMD Opteron/Athlon64 processors.

It is still possible to run SMP kernel on UP machine -- so this sounds
wrong.


It's possible to run a kernel with drivers for hardware you dont have. But not having the dependencies correct for those drivers for that hardware you dont have just because it's possible you can run a kernel with those drivers without that hardware isn't correct. Got it?

if an SMP K8 system needs ACPI_PROCESSOR for the cpufreq driver, then we need to make this dependency, just because you can configure your kernel to include drivers you dont need (like smp on a up system) doesn't mean that dependency is wrong, it just means you've configured your system with drivers you dont need. Looking up the acpi table on a UP system probably wont break anything, since the driver should check if it's not able to and fallback to non-acpi methods before failing completley. If it doesn't then this patch should be fine. Otherwise we'd need to add a check in the driver to see if we're actually running in an smp configuration and use the correct method.

The Kconfig dependency would still be valid in either case. If the lookup for acpi tables fails with no fallback to the non-acpi way of using the cpufreq driver, then we have to fix the driver.


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