There is some rare cases where CPB (and possibly IDA) are missing on processors.
This is the case fixed by commit f7f3dc00f612 ("x86/cpu/AMD: Fix erratum 1076 (CPB bit)") and following.
In such context, the boost status isn't reported by /sys/devices/system/cpu/cpufreq/boost.
This commit is about printing a message reporting the CPU doesn't expose the boost capabilities.
This message could help debugging platforms hit by this phenomena.
Signed-off-by: Erwan Velu <[email protected]>
---
drivers/cpufreq/acpi-cpufreq.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index d62fd374d5c7..06d32d21dac0 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -916,8 +916,10 @@ static void __init acpi_cpufreq_boost_init(void)
{
int ret;
- if (!(boot_cpu_has(X86_FEATURE_CPB) || boot_cpu_has(X86_FEATURE_IDA)))
+ if (!(boot_cpu_has(X86_FEATURE_CPB) || boot_cpu_has(X86_FEATURE_IDA))) {
+ pr_debug("CPU doesn't expose boost capabilities\n");
return;
+ }
acpi_cpufreq_driver.set_boost = set_boost;
acpi_cpufreq_driver.boost_enabled = boost_state(0);
--
2.20.1
On Wed, Feb 20, 2019 at 11:11 AM Erwan Velu <[email protected]> wrote:
>
> There is some rare cases where CPB (and possibly IDA) are missing on processors.
> This is the case fixed by commit f7f3dc00f612 ("x86/cpu/AMD: Fix erratum 1076 (CPB bit)") and following.
>
> In such context, the boost status isn't reported by /sys/devices/system/cpu/cpufreq/boost.
So I'm not really sure why the extra message is needed. It looks like
this message will always be printed (with debug output enabled) if the
current cpufreq driver is acpi-cpufreq and the boost attribute is not
present in sysfs, which only is the case if CPB/IDA aren't there.
Does it provide any additional information, then?
Le 20/02/2019 à 11:41, Rafael J. Wysocki a écrit :
> On Wed, Feb 20, 2019 at 11:11 AM Erwan Velu <[email protected]> wrote:
>> There is some rare cases where CPB (and possibly IDA) are missing on processors.
>> This is the case fixed by commit f7f3dc00f612 ("x86/cpu/AMD: Fix erratum 1076 (CPB bit)") and following.
>>
>> In such context, the boost status isn't reported by /sys/devices/system/cpu/cpufreq/boost.
> So I'm not really sure why the extra message is needed. It looks like
> this message will always be printed (with debug output enabled) if the
> current cpufreq driver is acpi-cpufreq and the boost attribute is not
> present in sysfs, which only is the case if CPB/IDA aren't there.
>
> Does it provide any additional information, then?
When you know and read the code, yes this patch is too obvious.
As a user when I was troubleshooting why the boost entry was _not_
populated on one CPU and was populated on another.
Running acpi-cpufreq with dyndbg, I would have found useful to get that
hint.
So that could helps users that never read that part of the code and
which are tricked into that configuration.
Erwan,
On Wed, Feb 20, 2019 at 11:52 AM Erwan Velu <[email protected]> wrote:
>
>
> Le 20/02/2019 à 11:41, Rafael J. Wysocki a écrit :
> > On Wed, Feb 20, 2019 at 11:11 AM Erwan Velu <[email protected]> wrote:
> >> There is some rare cases where CPB (and possibly IDA) are missing on processors.
> >> This is the case fixed by commit f7f3dc00f612 ("x86/cpu/AMD: Fix erratum 1076 (CPB bit)") and following.
> >>
> >> In such context, the boost status isn't reported by /sys/devices/system/cpu/cpufreq/boost.
> > So I'm not really sure why the extra message is needed. It looks like
> > this message will always be printed (with debug output enabled) if the
> > current cpufreq driver is acpi-cpufreq and the boost attribute is not
> > present in sysfs, which only is the case if CPB/IDA aren't there.
> >
> > Does it provide any additional information, then?
>
> When you know and read the code, yes this patch is too obvious.
>
> As a user when I was troubleshooting why the boost entry was _not_
> populated on one CPU and was populated on another.
>
> Running acpi-cpufreq with dyndbg, I would have found useful to get that
> hint.
>
> So that could helps users that never read that part of the code and
> which are tricked into that configuration.
OK, I see your point.
I'll queue up the patch, but I guess I'll change the message.
I tried to put the message in a way to stay neutral, not saying if its
a real error or not.
Just reporting we were not able to find any boost cap on it.
Erwan,
Le mer. 20 févr. 2019 à 12:16, Rafael J. Wysocki <[email protected]> a écrit :
>
> On Wed, Feb 20, 2019 at 11:52 AM Erwan Velu <[email protected]> wrote:
> >
> >
> > Le 20/02/2019 à 11:41, Rafael J. Wysocki a écrit :
> > > On Wed, Feb 20, 2019 at 11:11 AM Erwan Velu <[email protected]> wrote:
> > >> There is some rare cases where CPB (and possibly IDA) are missing on processors.
> > >> This is the case fixed by commit f7f3dc00f612 ("x86/cpu/AMD: Fix erratum 1076 (CPB bit)") and following.
> > >>
> > >> In such context, the boost status isn't reported by /sys/devices/system/cpu/cpufreq/boost.
> > > So I'm not really sure why the extra message is needed. It looks like
> > > this message will always be printed (with debug output enabled) if the
> > > current cpufreq driver is acpi-cpufreq and the boost attribute is not
> > > present in sysfs, which only is the case if CPB/IDA aren't there.
> > >
> > > Does it provide any additional information, then?
> >
> > When you know and read the code, yes this patch is too obvious.
> >
> > As a user when I was troubleshooting why the boost entry was _not_
> > populated on one CPU and was populated on another.
> >
> > Running acpi-cpufreq with dyndbg, I would have found useful to get that
> > hint.
> >
> > So that could helps users that never read that part of the code and
> > which are tricked into that configuration.
>
> OK, I see your point.
>
> I'll queue up the patch, but I guess I'll change the message.