linux-toradex.git/arch/x86/kernel/cpu/intel_epb.c, branch v6.16

x86/msr: Rename 'wrmsrl_on_cpu()' to 'wrmsrq_on_cpu()'

2025-04-10T09:59:05+00:00

Suggested-by: "H. Peter Anvin" 
Signed-off-by: Ingo Molnar 
Acked-by: Peter Zijlstra (Intel) 
Cc: Juergen Gross 
Cc: Dave Hansen 
Cc: Xin Li 
Cc: Linus Torvalds

x86/msr: Rename 'rdmsrl_on_cpu()' to 'rdmsrq_on_cpu()'

2025-04-10T09:59:00+00:00

Suggested-by: "H. Peter Anvin" 
Signed-off-by: Ingo Molnar 
Acked-by: Peter Zijlstra (Intel) 
Cc: Juergen Gross 
Cc: Dave Hansen 
Cc: Xin Li 
Cc: Linus Torvalds

x86/msr: Rename 'wrmsrl()' to 'wrmsrq()'

2025-04-10T09:58:33+00:00

Suggested-by: "H. Peter Anvin" 
Signed-off-by: Ingo Molnar 
Acked-by: Peter Zijlstra (Intel) 
Cc: Juergen Gross 
Cc: Dave Hansen 
Cc: Xin Li 
Cc: Linus Torvalds

x86/msr: Rename 'rdmsrl()' to 'rdmsrq()'

2025-04-10T09:58:27+00:00

Suggested-by: "H. Peter Anvin" 
Signed-off-by: Ingo Molnar 
Acked-by: Peter Zijlstra (Intel) 
Cc: Juergen Gross 
Cc: Dave Hansen 
Cc: Xin Li 
Cc: Linus Torvalds

x86/cpu/intel_epb: Switch to new Intel CPU model defines

2024-04-29T08:31:16+00:00

New CPU #defines encode vendor and family as well as model.

Signed-off-by: Tony Luck 
Signed-off-by: Dave Hansen 
Signed-off-by: Borislav Petkov (AMD) 
Link: https://lore.kernel.org/all/20240424181510.41733-1-tony.luck%40intel.com

x86/cpu/intel_epb: Don't rely on link order

2023-11-24T12:54:31+00:00

intel_epb_init() is called as a subsys_initcall() to register cpuhp
callbacks. The callbacks make use of get_cpu_device() which will return
NULL unless register_cpu() has been called. register_cpu() is called
from topology_init(), which is also a subsys_initcall().

This is fragile. Moving the register_cpu() to a different
subsys_initcall() leads to a NULL dereference during boot.

Make intel_epb_init() a late_initcall(), user-space can't provide a
policy before this point anyway.

Signed-off-by: James Morse 
Signed-off-by: Russell King (Oracle) 
Signed-off-by: Ingo Molnar 
Reviewed-by: Gavin Shan 
Acked-by: Rafael J. Wysocki

x86/cpu: Fix Gracemont uarch

2023-08-09T19:51:06+00:00

Alderlake N is an E-core only product using Gracemont
micro-architecture. It fits the pre-existing naming scheme perfectly
fine, adhere to it.

Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Rafael J. Wysocki 
Acked-by: Hans de Goede 
Link: https://lore.kernel.org/r/20230807150405.686834933@infradead.org

x86/intel_epb: Set Alder Lake N and Raptor Lake P normal EPB

2022-11-03T18:31:01+00:00

Intel processors support additional software hint called EPB ("Energy
Performance Bias") to guide the hardware heuristic of power management
features to favor increasing dynamic performance or conserve energy
consumption.

Since this EPB hint is processor specific, the same value of hint can
result in different behavior across generations of processors.

commit 4ecc933b7d1f ("x86: intel_epb: Allow model specific normal EPB
value")' introduced capability to update the default power up EPB
based on the CPU model and updated the default EPB to 7 for Alder Lake
mobile CPUs.

The same change is required for other Alder Lake-N and Raptor Lake-P
mobile CPUs as the current default of 6 results in higher uncore power
consumption. This increase in power is related to memory clock
frequency setting based on the EPB value.

Depending on the EPB the minimum memory frequency is set by the
firmware. At EPB = 7, the minimum memory frequency is 1/4th compared to
EPB = 6. This results in significant power saving for idle and
semi-idle workload on a Chrome platform.

For example Change in power and performance from EPB change from 6 to 7
on Alder Lake-N:

Workload Performance diff (%) power diff
----------------------------------------------------
VP9 FHD30 0 (FPS) -218 mw
Google meet 0 (FPS) -385 mw

This 200+ mw power saving is very significant for mobile platform for
battery life and thermal reasons.

But as the workload demands more memory bandwidth, the memory frequency
will be increased very fast. There is no power savings for such busy
workloads.

For example:

Workload Performance diff (%) from EPB 6 to 7
-------------------------------------------------------
Speedometer 2.0 -0.8
WebGL Aquarium 10K
Fish -0.5
Unity 3D 2018 0.2
WebXPRT3 -0.5

There are run to run variations for performance scores for
such busy workloads. So the difference is not significant.

Add a new define ENERGY_PERF_BIAS_NORMAL_POWERSAVE for EPB 7
and use it for Alder Lake-N and Raptor Lake-P mobile CPUs.

This modification is done originally by
Jeremy Compostella .

Signed-off-by: Srinivas Pandruvada
Signed-off-by: Dave Hansen
Reviewed-by: Rafael J. Wysocki
Link: https://lore.kernel.org/all/20221027220056.1534264-1-srinivas.pandruvada%40linux.intel.com

x86: intel_epb: Allow model specific normal EPB value

2022-01-04T15:37:23+00:00

The current EPB "normal" is defined as 6 and set whenever power-up EPB
value is 0. This setting resulted in the desired out of box power and
performance for several CPU generations. But this value is not suitable
for AlderLake mobile CPUs, as this resulted in higher uncore power.
Since EPB is model specific, this is not unreasonable to have different
behavior.

Allow a capability where "normal" EPB can be redefined. For AlderLake
mobile CPUs this desired normal value is 7.

Signed-off-by: Srinivas Pandruvada 
Signed-off-by: Rafael J. Wysocki

x86: intel_epb: Do not build when CONFIG_PM is unset

2019-05-30T08:58:36+00:00

Commit 9ed0985332a6 ("x86: intel_epb: Take CONFIG_PM into account")
prevented the majority of the Performance and Energy Bias Hint (EPB)
handling code from being built when CONFIG_PM is unset to fix a
regression introduced by commit b9c273babce7 ("PM / arch: x86:
MSR_IA32_ENERGY_PERF_BIAS sysfs interface").

In hindsight, however, it would be better to skip all of the EPB
handling code for CONFIG_PM unset as there really is no reason for
it to be there in that case.  Namely, if the EPB is not touched
by the kernel at all with CONFIG_PM unset, there is no need to
worry about modifying the EPB inadvertently on CPU online and since
the system will not suspend or hibernate then, there is no need to
worry about possible modifications of the EPB by the platform
firmware during system-wide PM transitions.

For this reason, revert the changes made by commit 9ed0985332a6
and only allow intel_epb.o to be built when CONFIG_PM is set.

Note that this changes the behavior of the kernels built with
CONFIG_PM unset as they will not modify the EPB on boot if it is
zero initially any more, so it is not a fix strictly speaking, but
users building their kernels with CONFIG_PM unset really should not
expect them to take energy efficiency into account.  Moreover, if
CONFIG_PM is unset for performance reasons, leaving EPB as set
initially by the platform firmware will actually be consistent
with the user's expectations.

Signed-off-by: Rafael J. Wysocki 
Acked-by: Ingo Molnar