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Message-Id: <20220819162547.141333-1-jeremy.linton@arm.com>
Date: Fri, 19 Aug 2022 11:25:45 -0500
From: Jeremy Linton <jeremy.linton@....com>
To: linux-acpi@...r.kernel.org
Cc: rafael@...nel.org, lenb@...nel.org, viresh.kumar@...aro.org,
robert.moore@...el.com, punit.agrawal@...edance.com,
lukasz.luba@....com, ionela.voinescu@....com,
pierre.gondois@....com, linux-kernel@...r.kernel.org,
devel@...ica.org, linux-pm@...r.kernel.org,
Jeremy Linton <jeremy.linton@....com>
Subject: [PATCH v4 0/2] Disable FIE on machines with slow counters
FIE assumes the delivered/relative perf registers are fast to read so
it goes ahead and hits them quite frequently. On a couple Arm
platforms though they end up in PCC regions which require mailbox
handshaking with other parts of the platform.
This results in a lot of overhead in the cppc_fie task. As such lets
runtime disable FIE if we detect it enabled on one of those platforms.
Also allow the user to manually enable/disable it via a module parameter.
v1->v2:
Apply Rafael's review comments.
Move the MODULE_PARAM into the ifdef
Fix compiler warning when ACPI_CPPC_LIB is disabled.
v2->v3:
Tristate the module param so FIE can be forced on/off
Bump pr_debug to pr_info if FIE is disabled due to PCC regions
Switch ACPI_CPPC_CPUFREQ_FIE off by default
v3->v4:
No functional change, resend due to email addr issues
Jeremy Linton (2):
ACPI: CPPC: Disable FIE if registers in PCC regions
cpufreq: CPPC: Change FIE default
drivers/acpi/cppc_acpi.c | 41 ++++++++++++++++++++++++++++++++++
drivers/cpufreq/Kconfig.arm | 2 +-
drivers/cpufreq/cppc_cpufreq.c | 31 +++++++++++++++++++++----
include/acpi/cppc_acpi.h | 5 +++++
4 files changed, 74 insertions(+), 5 deletions(-)
--
2.37.1
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