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[PATCH v4 3/6] clocksource/drivers/exynos_mct: Set local timer interrupts as percpu

Will McVicker posted 6 patches 3 months, 2 weeks ago
[PATCH v4 3/6] clocksource/drivers/exynos_mct: Set local timer interrupts as percpu
Posted by Will McVicker 3 months, 2 weeks ago 
From: Hosung Kim <hosung0.kim@samsung.com>

To allow the CPU to handle it's own clock events, we need to set the
IRQF_PERCPU flag. This prevents the local timer interrupts from
migrating to other CPUs.

Signed-off-by: Hosung Kim <hosung0.kim@samsung.com>
[Original commit from https://android.googlesource.com/kernel/gs/+/03267fad19f093bac979ca78309483e9eb3a8d16]
Reviewed-by: Peter Griffin <peter.griffin@linaro.org>
Reviewed-by: Youngmin Nam <youngmin.nam@samsung.com>
Tested-by: Youngmin Nam <youngmin.nam@samsung.com>
Signed-off-by: Will McVicker <willmcvicker@google.com>
---
 drivers/clocksource/exynos_mct.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
index 96361d5dc57d..a5ef7d64b1c2 100644
--- a/drivers/clocksource/exynos_mct.c
+++ b/drivers/clocksource/exynos_mct.c
@@ -596,7 +596,8 @@ static int __init exynos4_timer_interrupts(struct device_node *np,
 			irq_set_status_flags(mct_irq, IRQ_NOAUTOEN);
 			if (request_irq(mct_irq,
 					exynos4_mct_tick_isr,
-					IRQF_TIMER | IRQF_NOBALANCING,
+					IRQF_TIMER | IRQF_NOBALANCING |
+					IRQF_PERCPU,
 					pcpu_mevt->name, pcpu_mevt)) {
 				pr_err("exynos-mct: cannot register IRQ (cpu%d)\n",
 									cpu);
-- 
2.50.0.rc2.761.g2dc52ea45b-goog
Re: [PATCH v4 3/6] clocksource/drivers/exynos_mct: Set local timer interrupts as percpu
Posted by Marek Szyprowski 1 month, 1 week ago 
On 20.06.2025 20:17, Will McVicker wrote:
> From: Hosung Kim <hosung0.kim@samsung.com>
>
> To allow the CPU to handle it's own clock events, we need to set the
> IRQF_PERCPU flag. This prevents the local timer interrupts from
> migrating to other CPUs.
>
> Signed-off-by: Hosung Kim <hosung0.kim@samsung.com>
> [Original commit from https://android.googlesource.com/kernel/gs/+/03267fad19f093bac979ca78309483e9eb3a8d16]
> Reviewed-by: Peter Griffin <peter.griffin@linaro.org>
> Reviewed-by: Youngmin Nam <youngmin.nam@samsung.com>
> Tested-by: Youngmin Nam <youngmin.nam@samsung.com>
> Signed-off-by: Will McVicker <willmcvicker@google.com>

This patch has been merged some time ago to v6.17-rc1 as commit 
f3cec54ee3bf ("clocksource/drivers/exynos_mct: Set local timer 
interrupts as percpu"). Recently I found that it breaks CPU hotplug 
support for some 'little' cores on Exynos5422 based boards, like 
OdroidXU3/XU4:

# for i in /sys/devices/system/cpu/cpu[1-9]; do echo 0 >$i/online; done
# for i in /sys/devices/system/cpu/cpu[1-9]; do echo 1 >$i/online; done
[  117.100195] CPU2: failed to come online
-bash: echo: write error: Input/output error
[  118.140426] CPU3: failed to come online
-bash: echo: write error: Input/output error
[  118.148428] CPU4: detected I-Cache line size mismatch, workaround 
enabled
[  118.169613] CPU5: detected I-Cache line size mismatch, workaround 
enabled
[  118.216802] CPU6: detected I-Cache line size mismatch, workaround 
enabled
[  118.283725] CPU7: detected I-Cache line size mismatch, workaround 
enabled
#

Frankly speaking I have no idea why this happens. CPU hotplug was always 
broken for the CPU0, but this is not relevant for this case. Maybe this 
PERCPU flag should be applied only on ARM64-based boards to avoid 
affecting legacy ARM 32bit cases?

> ---
>   drivers/clocksource/exynos_mct.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
> index 96361d5dc57d..a5ef7d64b1c2 100644
> --- a/drivers/clocksource/exynos_mct.c
> +++ b/drivers/clocksource/exynos_mct.c
> @@ -596,7 +596,8 @@ static int __init exynos4_timer_interrupts(struct device_node *np,
>   			irq_set_status_flags(mct_irq, IRQ_NOAUTOEN);
>   			if (request_irq(mct_irq,
>   					exynos4_mct_tick_isr,
> -					IRQF_TIMER | IRQF_NOBALANCING,
> +					IRQF_TIMER | IRQF_NOBALANCING |
> +					IRQF_PERCPU,
>   					pcpu_mevt->name, pcpu_mevt)) {
>   				pr_err("exynos-mct: cannot register IRQ (cpu%d)\n",
>   									cpu);

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland
[tip: timers/clocksource] clocksource/drivers/exynos_mct: Set local timer interrupts as percpu
Posted by tip-bot2 for Hosung Kim 2 months, 2 weeks ago 
The following commit has been merged into the timers/clocksource branch of tip:

Commit-ID:     f3cec54ee3bfd50b90b9f3b7110b9357be97babe
Gitweb:        https://git.kernel.org/tip/f3cec54ee3bfd50b90b9f3b7110b9357be97babe
Author:        Hosung Kim <hosung0.kim@samsung.com>
AuthorDate:    Fri, 20 Jun 2025 11:17:06 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Fri, 25 Jul 2025 12:05:39 +02:00

clocksource/drivers/exynos_mct: Set local timer interrupts as percpu

To allow the CPU to handle its own clock events, we need to set the
IRQF_PERCPU flag. This prevents the local timer interrupts from
migrating to other CPUs.

Original commit from:

  https://android.googlesource.com/kernel/gs/+/03267fad19f093bac979ca78309483e9eb3a8d16

Signed-off-by: Hosung Kim <hosung0.kim@samsung.com>
Signed-off-by: Will McVicker <willmcvicker@google.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Youngmin Nam <youngmin.nam@samsung.com>
Reviewed-by: Peter Griffin <peter.griffin@linaro.org>
Reviewed-by: Youngmin Nam <youngmin.nam@samsung.com>
Link: https://lore.kernel.org/r/20250620181719.1399856-4-willmcvicker@google.com
---
 drivers/clocksource/exynos_mct.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
index 96361d5..a5ef7d6 100644
--- a/drivers/clocksource/exynos_mct.c
+++ b/drivers/clocksource/exynos_mct.c
@@ -596,7 +596,8 @@ static int __init exynos4_timer_interrupts(struct device_node *np,
 			irq_set_status_flags(mct_irq, IRQ_NOAUTOEN);
 			if (request_irq(mct_irq,
 					exynos4_mct_tick_isr,
-					IRQF_TIMER | IRQF_NOBALANCING,
+					IRQF_TIMER | IRQF_NOBALANCING |
+					IRQF_PERCPU,
 					pcpu_mevt->name, pcpu_mevt)) {
 				pr_err("exynos-mct: cannot register IRQ (cpu%d)\n",
 									cpu);
[tip: timers/clocksource] clocksource/drivers/exynos_mct: Set local timer interrupts as percpu
Posted by tip-bot2 for Hosung Kim 2 months, 2 weeks ago 
The following commit has been merged into the timers/clocksource branch of tip:

Commit-ID:     10934da577f627a97db18cf05dbe0c3c1b4a68d6
Gitweb:        https://git.kernel.org/tip/10934da577f627a97db18cf05dbe0c3c1b4a68d6
Author:        Hosung Kim <hosung0.kim@samsung.com>
AuthorDate:    Fri, 20 Jun 2025 11:17:06 -07:00
Committer:     Daniel Lezcano <daniel.lezcano@linaro.org>
CommitterDate: Tue, 15 Jul 2025 13:00:50 +02:00

clocksource/drivers/exynos_mct: Set local timer interrupts as percpu

To allow the CPU to handle it's own clock events, we need to set the
IRQF_PERCPU flag. This prevents the local timer interrupts from
migrating to other CPUs.

Signed-off-by: Hosung Kim <hosung0.kim@samsung.com>
[Original commit from https://android.googlesource.com/kernel/gs/+/03267fad19f093bac979ca78309483e9eb3a8d16]
Reviewed-by: Peter Griffin <peter.griffin@linaro.org>
Reviewed-by: Youngmin Nam <youngmin.nam@samsung.com>
Tested-by: Youngmin Nam <youngmin.nam@samsung.com>
Signed-off-by: Will McVicker <willmcvicker@google.com>
Link: https://lore.kernel.org/r/20250620181719.1399856-4-willmcvicker@google.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 drivers/clocksource/exynos_mct.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
index 96361d5..a5ef7d6 100644
--- a/drivers/clocksource/exynos_mct.c
+++ b/drivers/clocksource/exynos_mct.c
@@ -596,7 +596,8 @@ static int __init exynos4_timer_interrupts(struct device_node *np,
 			irq_set_status_flags(mct_irq, IRQ_NOAUTOEN);
 			if (request_irq(mct_irq,
 					exynos4_mct_tick_isr,
-					IRQF_TIMER | IRQF_NOBALANCING,
+					IRQF_TIMER | IRQF_NOBALANCING |
+					IRQF_PERCPU,
 					pcpu_mevt->name, pcpu_mevt)) {
 				pr_err("exynos-mct: cannot register IRQ (cpu%d)\n",
 									cpu);

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