From: tip-bot for Geert Uytterhoeven <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: daniel.lezcano@linaro.org, mingo@kernel.org,
geert+renesas@glider.be, tglx@linutronix.de,
linux-kernel@vger.kernel.org, peterz@infradead.org,
hpa@zytor.com, laurent.pinchart@ideasonboard.com
Subject: [tip:timers/urgent] clockevents/drivers/sh_cmt: Only perform clocksource suspend/resume if enabled
Date: Sun, 9 Aug 2015 03:25:44 -0700 [thread overview]
Message-ID: <tip-54d46b7fbcbd00fe4b20a27208e5909facc714e3@git.kernel.org> (raw)
In-Reply-To: <1438875126-12596-2-git-send-email-daniel.lezcano@linaro.org>
Commit-ID: 54d46b7fbcbd00fe4b20a27208e5909facc714e3
Gitweb: http://git.kernel.org/tip/54d46b7fbcbd00fe4b20a27208e5909facc714e3
Author: Geert Uytterhoeven <geert+renesas@glider.be>
AuthorDate: Thu, 6 Aug 2015 17:32:06 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Sat, 8 Aug 2015 10:50:08 +0200
clockevents/drivers/sh_cmt: Only perform clocksource suspend/resume if enabled
Currently the sh_cmt clocksource timer is disabled or enabled
unconditionally on clocksource suspend resp. resume, even if a
better clocksource is present (e.g. arch_sys_counter) and the
sh_cmt clocksource is not enabled.
As sh_cmt is a syscore device when its timer is enabled, this
may lead to a genpd.prepared_count imbalance in the presence of
PM Domains, which may cause a lock-up during reboot after s2ram.
During suspend:
- pm_genpd_prepare() is called for all non-syscore devices (incl.
sh_cmt), increasing genpd.prepared_count for each device,
- clocksource.suspend() is called for all clocksource devices,
- sh_cmt_clocksource_suspend() calls sh_cmt_stop(), which is a no-op
as the clocksource was not enabled.
During resume:
- clocksource.resume() is called for all clocksource devices,
- sh_cmt_clocksource_resume() calls sh_cmt_start(), which enables the
clocksource timer, and turns sh_cmt into a syscore device,
- pm_genpd_complete() is called for all non-syscore devices (excl.
sh_cmt now!), decreasing genpd.prepared_count for each device but
sh_cmt.
Now genpd.prepared_count of the PM Domain containing sh_cmt is
still 1 instead of zero. On subsequent suspend/resume cycles,
sh_cmt is still a syscore device, hence it's skipped for
pm_genpd_{prepare,complete}(), keeping the imbalance of
genpd.prepared_count at 1.
During reboot:
- platform_drv_shutdown() is called for any platform device that has
a driver with a .shutdown() method (only rcar-dmac on R-Car Gen2),
- platform_drv_shutdown() calls dev_pm_domain_detach(), which
calls genpd_dev_pm_detach(),
- genpd_dev_pm_detach() keeps calling pm_genpd_remove_device() until
it doesn't return -EAGAIN[*],
- If the device is part of the same PM Domain as sh_cmt,
pm_genpd_remove_device() always fails with -EAGAIN due to
genpd.prepared_count > 0.
- Infinite loop in genpd_dev_pm_detach()[*].
[*] Commit 93af5e9354432828 ("PM / Domains: Avoid infinite loops in
attach/detach code") already limited the number of loop iterations,
avoiding the lock-up.
To fix this, only disable or enable the clocksource timer on
clocksource suspend resp. resume if the clocksource was enabled.
This was tested on r8a7791/koelsch with the CPG Clock Domain:
- using arch_sys_counter as the clocksource, which is the default, and
which showed the problem,
- using sh_cmt as a clocksource ("echo ffca0000.timer > \
/sys/devices/system/clocksource/clocksource0/current_clocksource"),
which behaves the same as before.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1438875126-12596-2-git-send-email-daniel.lezcano@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
drivers/clocksource/sh_cmt.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/clocksource/sh_cmt.c b/drivers/clocksource/sh_cmt.c
index b8ff3c6..c96de14 100644
--- a/drivers/clocksource/sh_cmt.c
+++ b/drivers/clocksource/sh_cmt.c
@@ -661,6 +661,9 @@ static void sh_cmt_clocksource_suspend(struct clocksource *cs)
{
struct sh_cmt_channel *ch = cs_to_sh_cmt(cs);
+ if (!ch->cs_enabled)
+ return;
+
sh_cmt_stop(ch, FLAG_CLOCKSOURCE);
pm_genpd_syscore_poweroff(&ch->cmt->pdev->dev);
}
@@ -669,6 +672,9 @@ static void sh_cmt_clocksource_resume(struct clocksource *cs)
{
struct sh_cmt_channel *ch = cs_to_sh_cmt(cs);
+ if (!ch->cs_enabled)
+ return;
+
pm_genpd_syscore_poweron(&ch->cmt->pdev->dev);
sh_cmt_start(ch, FLAG_CLOCKSOURCE);
}
next prev parent reply other threads:[~2015-08-09 10:26 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-06 15:29 [PULL] clockevents: a couple of fixes for tip/timers/urgent Daniel Lezcano
2015-08-06 15:32 ` [PATCH 1/2] clockevents/drivers/timer-stm32: Improve dependencies of timer-stm32 Daniel Lezcano
2015-08-06 15:32 ` [PATCH 2/2] clockevents/drivers/sh_cmt: Only perform clocksource suspend/resume if enabled Daniel Lezcano
2015-08-09 10:25 ` tip-bot for Geert Uytterhoeven [this message]
2015-08-07 7:19 ` [PULL] clockevents: a couple of fixes for tip/timers/urgent Ingo Molnar
2015-08-07 21:25 ` Geert Uytterhoeven
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