Date:	Thu, 6 Sep 2012 22:53:07 +0200
From:	Sedat Dilek <sedat.dilek@...il.com>
To:	Andre Przywara <andre.przywara@....com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-next@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Matthew Garrett <mjg@...hat.com>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Thomas Renninger <trenn@...e.de>
Subject: Re: linux-next: Tree for Sept 6 (does not boot on AMD64)

On Thu, Sep 6, 2012 at 10:50 PM, Andre Przywara <andre.przywara@....com> wrote:
> On 09/06/2012 10:30 PM, Sedat Dilek wrote:
>>
>> On Thu, Sep 6, 2012 at 10:08 PM, Rafael J. Wysocki<rjw@...k.pl>  wrote:
>>>
>>> On Thursday, September 06, 2012, Sedat Dilek wrote:
>>>>
>>>> On Thu, Sep 6, 2012 at 1:48 PM, Sedat Dilek<sedat.dilek@...il.com>
>>>> wrote:
>>>>>
>>>>> On Thu, Sep 6, 2012 at 9:23 AM, Stephen Rothwell<sfr@...b.auug.org.au>
>>>>> wrote:
>>>>>>
>>>>>> Hi all,
>>>>>
>>>>> Hi,
>>>>>
>>>>>
>>>>> Unfortunately, today's linux-next does not boot here on Ubuntu/precise
>>>>> AMD64.
>>>>> My yesterday's next-20120905 is fine.
>>>>>
>>>>> I throw out all my additional patches an rebuild again as "-2", but
>>>>> this linux-image does not boot.
>>>>> It's in very early stage.
>>>>> I removed "quiet" etc. from kernel-command-line, but this reveals not
>>>>> much more.
>>>>>
>>>>>  From the attached kernel-config.diff:
>>>>> Dunno why the 2nd is disabled now and try to turn off the 1st one in a
>>>>> "-3" build.
>>>>>
>>>>> +CONFIG_X86_ACPI_CPUFREQ_CPB=y
>>>>> -CONFIG_USB_LIBUSUAL=y
>>>>>
>>>>
>>>> [ CC Rafael (cpufreq sub-maintainer) ]
>>>
>>>
>>> Well, this is related to the AMD cpufreq patchset I've just added to
>>> linux-next.  I'll drop it for now until the issue is resolved.
>>>
>>
>> Hi Rafael,
>>
>> The problem was caused by the slab/next merge (see [1]).
>>
>> [1] http://marc.info/?t=134695686500008&r=1&w=2
>>
>>>> I hacked to turn off CONFIG_X86_ACPI_CPUFREQ_CPB, but this is not the
>>>> root cause.
>>>> Not sure why this setting is default YES, Rafael?
>>>>
>>>> To switch from upstart to systemd does not help.
>>>
>>>
>>> Andre, care to have a look at this?
>>>
>>
>> I am not sure if the depends-on/default-n/default-y lines are correct.
>> Here, I am on a Intel sandy-bridge CPU, so why do I need to activate
>> any AMD CPU workaround?
>
>
> It is not a workaround, it is about keeping a feature that was in
> powernow-k8 for 2.5 years. AMD CPUs have this sysfs knob for turning on and
> off the boost feature, we want to keep this around for some time for
> compatibility reasons.
> Newer AMD CPUs (Phenoms/Barcelona and up) are now only supported by
> acpi-cpufreq, not by powernow-k8 anymore.
>
> And: it will only be activated on AMD:
> +#ifdef CONFIG_X86_ACPI_CPUFREQ_CPB
> ....
> +        * Lets enable it only on AMD CPUs for compatibility reasons and
> +        * only if configured. This is considered legacy code, which
> +        * will probably be removed at some point in the future.
> +        */
> +       if (check_amd_hwpstate_cpu(0)) {
> ...
>
>>
>> [ Linux-Next (next-20120906) ]
>>
>> 19 config X86_ACPI_CPUFREQ
>> 20         tristate "ACPI Processor P-States driver"
>> 21         select CPU_FREQ_TABLE
>> 22         depends on ACPI_PROCESSOR
>> 23         help
>> 24           This driver adds a CPUFreq driver which utilizes the ACPI
>> 25           Processor Performance States.
>> 26           This driver also supports Intel Enhanced Speedstep and newer
>> 27           AMD CPUs.
>> 28
>> 29           To compile this driver as a module, choose M here: the
>> 30           module will be called acpi-cpufreq.
>> 31
>> 32           For details, take a look at<file:Documentation/cpu-freq/>.
>> 33
>> 34           If in doubt, say N.
>> 35
>> 36 config X86_ACPI_CPUFREQ_CPB
>> 37         default y
>> 38         bool "Legacy cpb sysfs knob support for AMD CPUs"
>> 39         depends on X86_ACPI_CPUFREQ&&  CPU_SUP_AMD
>>
>> 40         help
>> 41           The powernow-k8 driver used to provide a sysfs knob called
>> "cpb"
>> 42           to disable the Core Performance Boosting feature of AMD CPUs.
>> This
>> 43           file has now been superseeded by the more generic "boost"
>> entry.
>> 44
>> 45           By enabling this option the acpi_cpufreq driver provides the
>> old
>> 46           entry in addition to the new boost ones, for compatibility
>> reasons.
>>
>> Why is there no depends-on "X86_POWERNOW_K8" (see above help-text)?
>
>
> Because this driver lost the support for newer CPUs and thus also this
> feature. We migrate this feature over to acpi-cpufreq.
>
>
>> I have set CONFIG_CPU_SUP_AMD=y which leads always to
>> CONFIG_X86_ACPI_CPUFREQ_CPB=y.
>> As said Intel SNB CPU!
>
>
> As said it does not hurt if you boot it on an Intel CPU, the code will not
> be run.
>
>
>>
>> What about this (untested)?
>>
>> ----- SNIP -----
>> config X86_ACPI_CPUFREQ_CPB
>>          bool "Legacy cpb sysfs knob support for AMD CPUs"
>>          depends on X86_ACPI_CPUFREQ
>>          default y if X86_POWERNOW_K8&&  CPU_SUP_AMD
>
>
> Powernow-K8 does not support CPB anymore, this code is now in acpi-cpufreq.
> So a dependency on the old driver does not help.
>
> Are there still any problems with this patchset? Or are you only wondering
> about the new config switch?
>

Just wondering... Fell over it when digging into my boot-problem (this
appeared as a new Kconfig option, so).
Thanks for the explanations!

- Sedat -

> Thanks for testing!
> Andre.
>
>
> --
> Andre Przywara
> AMD-Operating System Research Center (OSRC), Dresden, Germany
>
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