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* [PATCH] acpi-cpufreq: Skip initialization if a cpufreq driver exists
@ 2021-05-18 19:34 kyle.meyer
  2021-05-21 13:01 ` Rafael J. Wysocki
  0 siblings, 1 reply; 8+ messages in thread
From: kyle.meyer @ 2021-05-18 19:34 UTC (permalink / raw)
  To: rjw, viresh.kumar, linux-kernel; +Cc: Kyle Meyer

From: Kyle Meyer <kyle.meyer@hpe.com>

Revert part of commit 75c0758137c7a
("acpi-cpufreq: Fail initialization if driver cannot be registered").

acpi-cpufreq is mutually exclusive with intel_pstate, however,
acpi-cpufreq is loaded multiple times during startup while intel_pstate is
enabled. On systems using systemd the kernel triggers one uevent for each
device as a result of systemd-udev-trigger.service. The service exists to
retrigger all devices as uevents sent by the kernel before systemd-udevd
is running are missed. The delay caused by systemd-udevd repeatedly loading
the driver, getting a fail return, and unloading the driver twice per
logical CPU has a significant impact on the startup time, and can cause
some devices to be unavailable after reaching the root login prompt.

Load the driver once but skip initialization if a cpufreq driver exists by
changing the return value of cpufreq_get_current_driver() from -EEXIST to
0.

Signed-off-by: Kyle Meyer <kyle.meyer@hpe.com>
---
 drivers/cpufreq/acpi-cpufreq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index 7e7450453714..e79a945369d1 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -1003,7 +1003,7 @@ static int __init acpi_cpufreq_init(void)
 
 	/* don't keep reloading if cpufreq_driver exists */
 	if (cpufreq_get_current_driver())
-		return -EEXIST;
+		return 0;
 
 	pr_debug("%s\n", __func__);
 
-- 
2.26.2

^ permalink raw reply	[flat|nested] 8+ messages in thread
* [PATCH] acpi-cpufreq: Skip initialization if a cpufreq driver exists
@ 2021-05-21 22:19 ` Kyle Meyer
  0 siblings, 0 replies; 8+ messages in thread
From: Kyle Meyer @ 2021-05-21 22:19 UTC (permalink / raw)
  To: rjw, viresh.kumar, linux-kernel; +Cc: linux-pm, linux-acpi, Kyle Meyer

Revert part of commit 75c0758137c7a
("acpi-cpufreq: Fail initialization if driver cannot be registered").

acpi-cpufreq is mutually exclusive with intel_pstate, however,
acpi-cpufreq is loaded multiple times during startup while intel_pstate is
enabled. On systems using systemd the kernel triggers one uevent for each
device as a result of systemd-udev-trigger.service. The service exists to
retrigger all devices as uevents sent by the kernel before systemd-udevd
is running are missed. The delay caused by systemd-udevd repeatedly loading
the driver, getting a fail return, and unloading the driver twice per
logical CPU has a significant impact on the startup time, and can cause
some devices to be unavailable after reaching the root login prompt.

Load the driver once but skip initialization if a cpufreq driver exists by
changing the return value of cpufreq_get_current_driver() from -EEXIST to
0.

Signed-off-by: Kyle Meyer <kyle.meyer@hpe.com>
---
 drivers/cpufreq/acpi-cpufreq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index 7e7450453714..e79a945369d1 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -1003,7 +1003,7 @@ static int __init acpi_cpufreq_init(void)
 
 	/* don't keep reloading if cpufreq_driver exists */
 	if (cpufreq_get_current_driver())
-		return -EEXIST;
+		return 0;
 
 	pr_debug("%s\n", __func__);
 
-- 
2.26.2

^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2021-06-07 11:14 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-05-18 19:34 [PATCH] acpi-cpufreq: Skip initialization if a cpufreq driver exists kyle.meyer
2021-05-21 13:01 ` Rafael J. Wysocki
2021-05-21 22:19 Kyle Meyer
2021-05-21 22:19 ` Kyle Meyer
2021-05-24 14:16 ` Rafael J. Wysocki
2021-06-07  7:25   ` Viresh Kumar
2021-06-07 11:02     ` Rafael J. Wysocki
2021-06-07 11:14       ` Viresh Kumar

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