| Message ID | 1449596261-31005-2-git-send-email-geert+renesas@glider.be (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
diff --git a/drivers/clocksource/sh_cmt.c b/drivers/clocksource/sh_cmt.c index 7e4cd3473c7204f2..e4138e2a88f56b4e 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); }
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> (cherry picked from commit 54d46b7fbcbd00fe4b20a27208e5909facc714e3) Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> --- drivers/clocksource/sh_cmt.c | 6 ++++++ 1 file changed, 6 insertions(+)