Messages in this thread Patch in this message | | | From | Geert Uytterhoeven <> | Subject | [PATCH 1/2] clocksource: sh_cmt: Only perform clocksource suspend/resume if enabled | Date | Thu, 18 Jun 2015 12:22:33 +0200 |
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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().
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> --- 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 b8ff3c64cc452a16..c96de14036a0adeb 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); } -- 1.9.1
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