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From: Thomas Renninger <trenn@suse.de>
To: Andre Przywara <andre.przywara@amd.com>
Cc: Konrad Rzeszutek Wilk <konrad@kernel.org>,
	Andreas Herrmann <andreas.herrmann3@amd.com>,
	"Rafael J. Wysocki" <rjw@sisk.pl>,
	cpufreq@vger.kernel.org, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org, Matthew Garret <mjg@redhat.com>
Subject: Re: [PATCH 2/8 v2] acpi-cpufreq: Add quirk to disable _PSD usage on all AMD CPUs
Date: Mon, 17 Sep 2012 13:40:23 +0200	[thread overview]
Message-ID: <201209171340.23801.trenn@suse.de> (raw)
In-Reply-To: <5056D420.80808@amd.com>

On Monday, September 17, 2012 09:41:20 AM Andre Przywara wrote:
> On 09/15/2012 01:20 PM, Konrad Rzeszutek Wilk wrote:
> >
...
> This was to overcome some nasty interaction between the Windows 
> scheduler and their version of the ondemand governor.
Whoever is/was responsible for this, can you explain him/her that
this was a bad idea and why.

Is this part of a BKDG?
Can you point to a public spec and the exact wording of the
"Windows scheduler workaround" BIOS vendors shall do?

> +               pr_info_once(PFX "overriding BIOS provided _PSD data\n");
The message shows up on nearly every platform wether a _PSD
function exists or not. This is wrong.

If it's _PSD info that should get ignored/overwritten, this should
be done where _PSD is obtained:
processor_perflib.c

Are you sure that it will never make sense for AMD to make use of
_PSD tables?
If yes, then always ignoring might be an option.

If not, this might need a more specific check, e.g.:
   - Latest Windows version support called via OSI interface?
        Latest Windowses should/may not need this anymore?
   - Check for Desktop CPUs that are affected by the bad spec?

Hm, as powernow-k8 never made use of _PSD, ignoring it for
now sounds like a good thing to do. Still the ignoring should get
moved to processor_perflib.c, best with a pointer or at least
a comment that _PSD can be dangerous on AMD platforms. At some
day _PSD may make sense for AMD platforms as well?


    Thomas

  reply	other threads:[~2012-09-17 11:40 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-09-04  8:28 [PATCH 0/8 v2] acpi-cpufreq: Move modern AMD cpufreq support to acpi-cpufreq Andre Przywara
2012-09-04  8:28 ` [PATCH 1/8 v2] acpi-cpufreq: Add support for modern AMD CPUs Andre Przywara
2012-09-04  8:28 ` [PATCH 2/8 v2] acpi-cpufreq: Add quirk to disable _PSD usage on all " Andre Przywara
     [not found]   ` <CACJDEmrOoZ_azqTrtfoGC-O=H0V=AHy8VExoFYYPhbUUx+7UAg@mail.gmail.com>
2012-09-17  7:41     ` Andre Przywara
2012-09-17 11:40       ` Thomas Renninger [this message]
2012-09-04  8:28 ` [PATCH 3/8 v2] cpufreq: Add warning message to powernow-k8 Andre Przywara
2012-09-04  8:28 ` [PATCH 4/8 v2] powernow-k8: delay info messages until initialization has succeeded Andre Przywara
2012-09-04  8:28 ` [PATCH 5/8 v2] ACPI: Add fixups for AMD P-state figures Andre Przywara
2012-09-04  8:28 ` [PATCH 6/8 v2] acpi-cpufreq: Add support for disabling dynamic overclocking Andre Przywara
2012-09-04  8:28 ` [PATCH 7/8 v2] acpi-cpufreq: Add compatibility for legacy AMD cpb sysfs knob Andre Przywara
2012-09-04  8:28 ` [PATCH 8/8 v2] cpufreq: Remove support for hardware P-state chips from powernow-k8 Andre Przywara
2012-09-05 13:46 ` [PATCH 0/8 v2] acpi-cpufreq: Move modern AMD cpufreq support to acpi-cpufreq Rafael J. Wysocki
2012-09-05 14:25   ` Thomas Renninger
2012-09-05 15:05     ` Andre Przywara

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