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Wed, 10 Sep 2025 10:27:16 -0400 (EDT) From: =?UTF-8?q?Niklas=20S=C3=B6derlund?= To: Daniel Lezcano , Thomas Gleixner , Geert Uytterhoeven , linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org Cc: =?UTF-8?q?Niklas=20S=C3=B6derlund?= , Geert Uytterhoeven Subject: [PATCH v2 1/2] clocksource/drivers/sh_cmt: Split start/stop of clock source and events Date: Wed, 10 Sep 2025 16:26:56 +0200 Message-ID: <20250910142657.1148696-2-niklas.soderlund+renesas@ragnatech.se> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250910142657.1148696-1-niklas.soderlund+renesas@ragnatech.se> References: <20250910142657.1148696-1-niklas.soderlund+renesas@ragnatech.se> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The CMT do a housekeeping such as dealing with runtime PM and enable/disable clocks when either a clock source is enabled, or when a new clock event is registered. Doing this type of housekeeping for when a clock event is registered is not always possible as it can happen in contexts where holding spinlocks is not possible. However doing it when registering a clock source is possible. As a first step to address this design break apart the CMT start and stop functions. The path for clock sources need not change, while the one for clock events need to be reworked in future work. There is no indented functional change, just breaking the two use-cases controlled by a flag into two distinct functions. Signed-off-by: Niklas S=C3=B6derlund Tested-by: Geert Uytterhoeven --- drivers/clocksource/sh_cmt.c | 94 ++++++++++++++++++++++++------------ 1 file changed, 64 insertions(+), 30 deletions(-) diff --git a/drivers/clocksource/sh_cmt.c b/drivers/clocksource/sh_cmt.c index b72b36e0abed..385eb94bbe7c 100644 --- a/drivers/clocksource/sh_cmt.c +++ b/drivers/clocksource/sh_cmt.c @@ -578,37 +578,74 @@ static irqreturn_t sh_cmt_interrupt(int irq, void *de= v_id) return IRQ_HANDLED; } =20 -static int sh_cmt_start(struct sh_cmt_channel *ch, unsigned long flag) +static int sh_cmt_start_clocksource(struct sh_cmt_channel *ch) { int ret =3D 0; unsigned long flags; =20 - if (flag & FLAG_CLOCKSOURCE) - pm_runtime_get_sync(&ch->cmt->pdev->dev); + pm_runtime_get_sync(&ch->cmt->pdev->dev); =20 raw_spin_lock_irqsave(&ch->lock, flags); =20 - if (!(ch->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE))) { - if (flag & FLAG_CLOCKEVENT) - pm_runtime_get_sync(&ch->cmt->pdev->dev); + if (!(ch->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE))) ret =3D sh_cmt_enable(ch); - } =20 if (ret) goto out; - ch->flags |=3D flag; + + ch->flags |=3D FLAG_CLOCKSOURCE; =20 /* setup timeout if no clockevent */ - if (ch->cmt->num_channels =3D=3D 1 && - flag =3D=3D FLAG_CLOCKSOURCE && (!(ch->flags & FLAG_CLOCKEVENT))) + if (ch->cmt->num_channels =3D=3D 1 && !(ch->flags & FLAG_CLOCKEVENT)) __sh_cmt_set_next(ch, ch->max_match_value); +out: + raw_spin_unlock_irqrestore(&ch->lock, flags); + + return ret; +} + +static void sh_cmt_stop_clocksource(struct sh_cmt_channel *ch) +{ + unsigned long flags; + unsigned long f; + + raw_spin_lock_irqsave(&ch->lock, flags); + + f =3D ch->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE); + + ch->flags &=3D ~FLAG_CLOCKSOURCE; + + if (f && !(ch->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE))) + sh_cmt_disable(ch); + + raw_spin_unlock_irqrestore(&ch->lock, flags); + + pm_runtime_put(&ch->cmt->pdev->dev); +} + +static int sh_cmt_start_clockevent(struct sh_cmt_channel *ch) +{ + int ret =3D 0; + unsigned long flags; + + raw_spin_lock_irqsave(&ch->lock, flags); + + if (!(ch->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE))) { + pm_runtime_get_sync(&ch->cmt->pdev->dev); + ret =3D sh_cmt_enable(ch); + } + + if (ret) + goto out; + + ch->flags |=3D FLAG_CLOCKEVENT; out: raw_spin_unlock_irqrestore(&ch->lock, flags); =20 return ret; } =20 -static void sh_cmt_stop(struct sh_cmt_channel *ch, unsigned long flag) +static void sh_cmt_stop_clockevent(struct sh_cmt_channel *ch) { unsigned long flags; unsigned long f; @@ -616,22 +653,19 @@ static void sh_cmt_stop(struct sh_cmt_channel *ch, un= signed long flag) raw_spin_lock_irqsave(&ch->lock, flags); =20 f =3D ch->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE); - ch->flags &=3D ~flag; + + ch->flags &=3D ~FLAG_CLOCKEVENT; =20 if (f && !(ch->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE))) { sh_cmt_disable(ch); - if (flag & FLAG_CLOCKEVENT) - pm_runtime_put(&ch->cmt->pdev->dev); - } - - /* adjust the timeout to maximum if only clocksource left */ - if ((flag =3D=3D FLAG_CLOCKEVENT) && (ch->flags & FLAG_CLOCKSOURCE)) - __sh_cmt_set_next(ch, ch->max_match_value); - - raw_spin_unlock_irqrestore(&ch->lock, flags); - - if (flag & FLAG_CLOCKSOURCE) pm_runtime_put(&ch->cmt->pdev->dev); + } + + /* adjust the timeout to maximum if only clocksource left */ + if (ch->flags & FLAG_CLOCKSOURCE) + __sh_cmt_set_next(ch, ch->max_match_value); + + raw_spin_unlock_irqrestore(&ch->lock, flags); } =20 static struct sh_cmt_channel *cs_to_sh_cmt(struct clocksource *cs) @@ -672,7 +706,7 @@ static int sh_cmt_clocksource_enable(struct clocksource= *cs) =20 ch->total_cycles =3D 0; =20 - ret =3D sh_cmt_start(ch, FLAG_CLOCKSOURCE); + ret =3D sh_cmt_start_clocksource(ch); if (!ret) ch->cs_enabled =3D true; =20 @@ -685,7 +719,7 @@ static void sh_cmt_clocksource_disable(struct clocksour= ce *cs) =20 WARN_ON(!ch->cs_enabled); =20 - sh_cmt_stop(ch, FLAG_CLOCKSOURCE); + sh_cmt_stop_clocksource(ch); ch->cs_enabled =3D false; } =20 @@ -696,7 +730,7 @@ static void sh_cmt_clocksource_suspend(struct clocksour= ce *cs) if (!ch->cs_enabled) return; =20 - sh_cmt_stop(ch, FLAG_CLOCKSOURCE); + sh_cmt_stop_clocksource(ch); dev_pm_genpd_suspend(&ch->cmt->pdev->dev); } =20 @@ -708,7 +742,7 @@ static void sh_cmt_clocksource_resume(struct clocksourc= e *cs) return; =20 dev_pm_genpd_resume(&ch->cmt->pdev->dev); - sh_cmt_start(ch, FLAG_CLOCKSOURCE); + sh_cmt_start_clocksource(ch); } =20 static int sh_cmt_register_clocksource(struct sh_cmt_channel *ch, @@ -740,7 +774,7 @@ static struct sh_cmt_channel *ced_to_sh_cmt(struct cloc= k_event_device *ced) =20 static void sh_cmt_clock_event_start(struct sh_cmt_channel *ch, int period= ic) { - sh_cmt_start(ch, FLAG_CLOCKEVENT); + sh_cmt_start_clockevent(ch); =20 if (periodic) sh_cmt_set_next(ch, ((ch->cmt->rate + HZ/2) / HZ) - 1); @@ -752,7 +786,7 @@ static int sh_cmt_clock_event_shutdown(struct clock_eve= nt_device *ced) { struct sh_cmt_channel *ch =3D ced_to_sh_cmt(ced); =20 - sh_cmt_stop(ch, FLAG_CLOCKEVENT); + sh_cmt_stop_clockevent(ch); return 0; } =20 @@ -763,7 +797,7 @@ static int sh_cmt_clock_event_set_state(struct clock_ev= ent_device *ced, =20 /* deal with old setting first */ if (clockevent_state_oneshot(ced) || clockevent_state_periodic(ced)) - sh_cmt_stop(ch, FLAG_CLOCKEVENT); + sh_cmt_stop_clockevent(ch); =20 dev_info(&ch->cmt->pdev->dev, "ch%u: used for %s clock events\n", ch->index, periodic ? 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Wed, 10 Sep 2025 10:27:18 -0400 (EDT) From: =?UTF-8?q?Niklas=20S=C3=B6derlund?= To: Daniel Lezcano , Thomas Gleixner , Geert Uytterhoeven , linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org Cc: =?UTF-8?q?Niklas=20S=C3=B6derlund?= Subject: [PATCH v2 2/2] clocksource/drivers/sh_cmt: Do not power down channels used for events Date: Wed, 10 Sep 2025 16:26:57 +0200 Message-ID: <20250910142657.1148696-3-niklas.soderlund+renesas@ragnatech.se> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250910142657.1148696-1-niklas.soderlund+renesas@ragnatech.se> References: <20250910142657.1148696-1-niklas.soderlund+renesas@ragnatech.se> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The CMT do runtime PM and call clk_enable()/clk_disable() when a new clock event is register and the CMT is not already started. This is not always possible as a spinlock is also needed to sync the internals of the CMT. Running with PROVE_LOCKING uncovers one such issue. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D [ BUG: Invalid wait context ] 6.17.0-rc3-arm64-renesas-03071-gb3c4f4122b28-dirty #21 Not tainted ----------------------------- swapper/1/0 is trying to lock: ffff00000898d180 (&dev->power.lock){-...}-{3:3}, at: __pm_runtime_resum= e+0x38/0x88 ccree e6601000.crypto: ARM CryptoCell 630P Driver: HW version 0xAF40000= 1/0xDCC63000, Driver version 5.0 other info that might help us debug this: ccree e6601000.crypto: ARM ccree device initialized context-{5:5} 2 locks held by swapper/1/0: #0: ffff80008173c298 (tick_broadcast_lock){-...}-{2:2}, at: __tick_bro= adcast_oneshot_control+0xa4/0x3a8 #1: ffff0000089a5858 (&ch->lock){....}-{2:2} usbcore: registered new interface driver usbhid , at: sh_cmt_start+0x30/0x364 stack backtrace: CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted 6.17.0-rc3-arm64-renes= as-03071-gb3c4f4122b28-dirty #21 PREEMPT Hardware name: Renesas Salvator-X 2nd version board based on r8a77965 (= DT) Call trace: show_stack+0x14/0x1c (C) dump_stack_lvl+0x6c/0x90 dump_stack+0x14/0x1c __lock_acquire+0x904/0x1584 lock_acquire+0x220/0x34c _raw_spin_lock_irqsave+0x58/0x80 __pm_runtime_resume+0x38/0x88 sh_cmt_start+0x54/0x364 sh_cmt_clock_event_set_oneshot+0x64/0xb8 clockevents_switch_state+0xfc/0x13c tick_broadcast_set_event+0x30/0xa4 __tick_broadcast_oneshot_control+0x1e0/0x3a8 tick_broadcast_oneshot_control+0x30/0x40 cpuidle_enter_state+0x40c/0x680 cpuidle_enter+0x30/0x40 do_idle+0x1f4/0x26c cpu_startup_entry+0x34/0x40 secondary_start_kernel+0x11c/0x13c __secondary_switched+0x74/0x78 Fix this by unconditionally powering on and enabling the needed clocks for all CMT channels which are used for clock events. Do this before registering any clock source or event to avid having to take the spin lock at probe time. Signed-off-by: Niklas S=C3=B6derlund --- * Changes since v1 - Move the unconditional power on case before registering any clock source or event to avoid having to use the spinlock to synchronize the powerup sequence in probe. --- drivers/clocksource/sh_cmt.c | 91 +++++++++++++++++------------------- 1 file changed, 42 insertions(+), 49 deletions(-) diff --git a/drivers/clocksource/sh_cmt.c b/drivers/clocksource/sh_cmt.c index 385eb94bbe7c..1d91730ee3cb 100644 --- a/drivers/clocksource/sh_cmt.c +++ b/drivers/clocksource/sh_cmt.c @@ -5,6 +5,7 @@ * Copyright (C) 2008 Magnus Damm */ =20 +#include #include #include #include @@ -623,51 +624,6 @@ static void sh_cmt_stop_clocksource(struct sh_cmt_chan= nel *ch) pm_runtime_put(&ch->cmt->pdev->dev); } =20 -static int sh_cmt_start_clockevent(struct sh_cmt_channel *ch) -{ - int ret =3D 0; - unsigned long flags; - - raw_spin_lock_irqsave(&ch->lock, flags); - - if (!(ch->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE))) { - pm_runtime_get_sync(&ch->cmt->pdev->dev); - ret =3D sh_cmt_enable(ch); - } - - if (ret) - goto out; - - ch->flags |=3D FLAG_CLOCKEVENT; - out: - raw_spin_unlock_irqrestore(&ch->lock, flags); - - return ret; -} - -static void sh_cmt_stop_clockevent(struct sh_cmt_channel *ch) -{ - unsigned long flags; - unsigned long f; - - raw_spin_lock_irqsave(&ch->lock, flags); - - f =3D ch->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE); - - ch->flags &=3D ~FLAG_CLOCKEVENT; - - if (f && !(ch->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE))) { - sh_cmt_disable(ch); - pm_runtime_put(&ch->cmt->pdev->dev); - } - - /* adjust the timeout to maximum if only clocksource left */ - if (ch->flags & FLAG_CLOCKSOURCE) - __sh_cmt_set_next(ch, ch->max_match_value); - - raw_spin_unlock_irqrestore(&ch->lock, flags); -} - static struct sh_cmt_channel *cs_to_sh_cmt(struct clocksource *cs) { return container_of(cs, struct sh_cmt_channel, cs); @@ -774,19 +730,30 @@ static struct sh_cmt_channel *ced_to_sh_cmt(struct cl= ock_event_device *ced) =20 static void sh_cmt_clock_event_start(struct sh_cmt_channel *ch, int period= ic) { - sh_cmt_start_clockevent(ch); - if (periodic) sh_cmt_set_next(ch, ((ch->cmt->rate + HZ/2) / HZ) - 1); else sh_cmt_set_next(ch, ch->max_match_value); } =20 +static void sh_cmt_clock_event_stop(struct sh_cmt_channel *ch) +{ + unsigned long flags; + + raw_spin_lock_irqsave(&ch->lock, flags); + + /* adjust the timeout to maximum if only clocksource left */ + if (ch->flags & FLAG_CLOCKSOURCE) + __sh_cmt_set_next(ch, ch->max_match_value); + + raw_spin_unlock_irqrestore(&ch->lock, flags); +} + static int sh_cmt_clock_event_shutdown(struct clock_event_device *ced) { struct sh_cmt_channel *ch =3D ced_to_sh_cmt(ced); =20 - sh_cmt_stop_clockevent(ch); + sh_cmt_clock_event_stop(ch); return 0; } =20 @@ -797,7 +764,7 @@ static int sh_cmt_clock_event_set_state(struct clock_ev= ent_device *ced, =20 /* deal with old setting first */ if (clockevent_state_oneshot(ced) || clockevent_state_periodic(ced)) - sh_cmt_stop_clockevent(ch); + sh_cmt_clock_event_stop(ch); =20 dev_info(&ch->cmt->pdev->dev, "ch%u: used for %s clock events\n", ch->index, periodic ? "periodic" : "oneshot"); @@ -968,6 +935,32 @@ static int sh_cmt_setup_channel(struct sh_cmt_channel = *ch, unsigned int index, ch->match_value =3D ch->max_match_value; raw_spin_lock_init(&ch->lock); =20 + if (clockevent) { + /* + * To support clock events the CMT must always be ready to + * accept new events, start it and leave no way for it to be + * turned off. + * + * This is OK as we can't never unregister a CMT device. If this + * is fixed in future an equal unconditional shutdown is needed. + * + * We don't need to hold the channel lock here as we have not + * yet register any clock source or event so there is no + * possible race. And holding the spinlock at probe time + * produces lockdep warnings. + */ + pm_runtime_get_sync(&ch->cmt->pdev->dev); + ret =3D sh_cmt_enable(ch); + if (ret) + return ret; + + /* + * Flag that the channel is used as a clock event, it's not + * allowed to be powered off! + */ + ch->flags |=3D FLAG_CLOCKEVENT; + } + ret =3D sh_cmt_register(ch, dev_name(&cmt->pdev->dev), clockevent, clocksource); if (ret) { --=20 2.51.0