[PATCH 0/6] adapt clockevents frequencies to mono clock: prerequisites 1

[PATCH 0/6] adapt clockevents frequencies to mono clock: prerequisites 1

[Nicolai Stange]

Hi,

in order to facilitate review, this (sub-)series has been split off from
a larger effort to be found at [1].

The overall goal is to adjust the clockevent devices' frequencies to the
NTP controlled monotonic time.

As a prerequisite, ced drivers must not alter the rate by any means other
than clockevents_update_freq() after registration.

The four drivers touched here are the only ones currently violating this.
What's more, altering the ced rates after registration isn't really
necessary for any of them. This series cleans this up.

John signaled willingness to deal with all of this and thus, it would be
best if all the patches herein would get picked by him only...

Based on v4.10-rc2.

Thanks,

Nicolai

[1] Current version:
      git://nicst.de/linux.git cev-freq-adj.v9.4.10-rc2
      http://nicst.de/git/?p=linux.git;a=shortlog;h=refs/heads/cev-freq-adj.v9.4.10-rc2

    Slightly outdated LKML submission:
      http://lkml.kernel.org/r/20161119160055.12491-1-nicstange@gmail.com

Nicolai Stange (6):
  clocksource: sh_cmt: compute rate before registration again
  clocksource: sh_tmu: compute rate before registration again
  clocksource: em_sti: split clock prepare and enable steps
  clocksource: em_sti: compute rate before registration
  clocksource: h8300_timer8: don't reset rate in ->set_state_oneshot()
  clockevents: make clockevents_config() static

 drivers/clocksource/em_sti.c       | 46 +++++++++++++++++++++-----------------
 drivers/clocksource/h8300_timer8.c |  8 -------
 drivers/clocksource/sh_cmt.c       | 45 ++++++++++++++++++++-----------------
 drivers/clocksource/sh_tmu.c       | 26 ++++++++++-----------
 include/linux/clockchips.h         |  1 -
 kernel/time/clockevents.c          |  2 +-
 6 files changed, 65 insertions(+), 63 deletions(-)

-- 
2.11.1

[PATCH 1/6] clocksource: sh_cmt: compute rate before registration again

[Nicolai Stange]

With the upcoming NTP correction related rate adjustments to be implemented
in the clockevents core, the latter needs to get informed about every rate
change of a clockevent device made after its registration.

Currently, sh_cmt violates this requirement in that it registers its
clockevent device with a dummy rate and sets its final ->mult and ->shift
values from its ->set_state_oneshot() and ->set_state_periodic() functions
respectively.

This patch moves the setting of the clockevent device's ->mult and ->shift
values to before its registration.

Note that there has been some back and forth regarding this question with
respect to the clocksource also provided by this driver:
  commit f4d7c3565c16 ("clocksource: sh_cmt: compute mult and shift before
                        registration")
moves the rate determination from the clocksource's ->enable() function to
before its registration. OTOH, the later
  commit 3593f5fe40a1 ("clocksource: sh_cmt: __clocksource_updatefreq_hz()
                        update")
basically reverts this, saying
  "Without this patch the old code uses clocksource_register() together
   with a hack that assumes a never changing clock rate."

However, I checked all current sh_cmt users in arch/sh as well as in
arch/arm/mach-shmobile carefully and right now, none of them changes any
rate in any clock tree relevant to sh_cmt after their respective
time_init(). Since all sh_cmt instances are created after time_init(), none
of them should ever observe any clock rate changes.

What's more, both, a clocksource as well as a clockevent device, can
immediately get selected for use at their registration and thus, enabled
at this point already. So it's probably safer to assume a "never changing
clock rate" here.

- Move the struct sh_cmt_channel's ->rate member to struct sh_cmt_device:
  it's a property of the underlying clock which is in turn specific to
  the sh_cmt_device.
- Determine the ->rate value in sh_cmt_setup() at device probing rather
  than at first usage.
- Set the clockevent device's ->mult and ->shift values right before its
  registration.
- Although not strictly necessary for the upcoming clockevent core changes,
  set the clocksource's rate at its registration for consistency.

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
---

Notes:
    For a detailed analysis of the current sh_cmt users, please see
    https://nicst.de/ced-clk-rate-change-analysis/sh_cmt-cgitted.html
    
    Compile-only tested on ARCH=sh and ARCH=arm.

 drivers/clocksource/sh_cmt.c | 45 ++++++++++++++++++++++++--------------------
 1 file changed, 25 insertions(+), 20 deletions(-)

diff --git a/drivers/clocksource/sh_cmt.c b/drivers/clocksource/sh_cmt.c
index 28757edf6aca..e3bf3baa12cc 100644
--- a/drivers/clocksource/sh_cmt.c
+++ b/drivers/clocksource/sh_cmt.c
@@ -103,7 +103,6 @@ struct sh_cmt_channel {
 	unsigned long match_value;
 	unsigned long next_match_value;
 	unsigned long max_match_value;
-	unsigned long rate;
 	raw_spinlock_t lock;
 	struct clock_event_device ced;
 	struct clocksource cs;
@@ -118,6 +117,7 @@ struct sh_cmt_device {
 
 	void __iomem *mapbase;
 	struct clk *clk;
+	unsigned long rate;
 
 	raw_spinlock_t lock; /* Protect the shared start/stop register */
 
@@ -320,7 +320,7 @@ static void sh_cmt_start_stop_ch(struct sh_cmt_channel *ch, int start)
 	raw_spin_unlock_irqrestore(&ch->cmt->lock, flags);
 }
 
-static int sh_cmt_enable(struct sh_cmt_channel *ch, unsigned long *rate)
+static int sh_cmt_enable(struct sh_cmt_channel *ch)
 {
 	int k, ret;
 
@@ -340,11 +340,9 @@ static int sh_cmt_enable(struct sh_cmt_channel *ch, unsigned long *rate)
 
 	/* configure channel, periodic mode and maximum timeout */
 	if (ch->cmt->info->width == 16) {
-		*rate = clk_get_rate(ch->cmt->clk) / 512;
 		sh_cmt_write_cmcsr(ch, SH_CMT16_CMCSR_CMIE |
 				   SH_CMT16_CMCSR_CKS512);
 	} else {
-		*rate = clk_get_rate(ch->cmt->clk) / 8;
 		sh_cmt_write_cmcsr(ch, SH_CMT32_CMCSR_CMM |
 				   SH_CMT32_CMCSR_CMTOUT_IE |
 				   SH_CMT32_CMCSR_CMR_IRQ |
@@ -572,7 +570,7 @@ static int sh_cmt_start(struct sh_cmt_channel *ch, unsigned long flag)
 	raw_spin_lock_irqsave(&ch->lock, flags);
 
 	if (!(ch->flags & (FLAG_CLOCKEVENT | FLAG_CLOCKSOURCE)))
-		ret = sh_cmt_enable(ch, &ch->rate);
+		ret = sh_cmt_enable(ch);
 
 	if (ret)
 		goto out;
@@ -640,10 +638,9 @@ static int sh_cmt_clocksource_enable(struct clocksource *cs)
 	ch->total_cycles = 0;
 
 	ret = sh_cmt_start(ch, FLAG_CLOCKSOURCE);
-	if (!ret) {
-		__clocksource_update_freq_hz(cs, ch->rate);
+	if (!ret)
 		ch->cs_enabled = true;
-	}
+
 	return ret;
 }
 
@@ -697,8 +694,7 @@ static int sh_cmt_register_clocksource(struct sh_cmt_channel *ch,
 	dev_info(&ch->cmt->pdev->dev, "ch%u: used as clock source\n",
 		 ch->index);
 
-	/* Register with dummy 1 Hz value, gets updated in ->enable() */
-	clocksource_register_hz(cs, 1);
+	clocksource_register_hz(cs, ch->cmt->rate);
 	return 0;
 }
 
@@ -709,19 +705,10 @@ static struct sh_cmt_channel *ced_to_sh_cmt(struct clock_event_device *ced)
 
 static void sh_cmt_clock_event_start(struct sh_cmt_channel *ch, int periodic)
 {
-	struct clock_event_device *ced = &ch->ced;
-
 	sh_cmt_start(ch, FLAG_CLOCKEVENT);
 
-	/* TODO: calculate good shift from rate and counter bit width */
-
-	ced->shift = 32;
-	ced->mult = div_sc(ch->rate, NSEC_PER_SEC, ced->shift);
-	ced->max_delta_ns = clockevent_delta2ns(ch->max_match_value, ced);
-	ced->min_delta_ns = clockevent_delta2ns(0x1f, ced);
-
 	if (periodic)
-		sh_cmt_set_next(ch, ((ch->rate + HZ/2) / HZ) - 1);
+		sh_cmt_set_next(ch, ((ch->cmt->rate + HZ/2) / HZ) - 1);
 	else
 		sh_cmt_set_next(ch, ch->max_match_value);
 }
@@ -824,6 +811,12 @@ static int sh_cmt_register_clockevent(struct sh_cmt_channel *ch,
 	ced->suspend = sh_cmt_clock_event_suspend;
 	ced->resume = sh_cmt_clock_event_resume;
 
+	/* TODO: calculate good shift from rate and counter bit width */
+	ced->shift = 32;
+	ced->mult = div_sc(ch->cmt->rate, NSEC_PER_SEC, ced->shift);
+	ced->max_delta_ns = clockevent_delta2ns(ch->max_match_value, ced);
+	ced->min_delta_ns = clockevent_delta2ns(0x1f, ced);
+
 	dev_info(&ch->cmt->pdev->dev, "ch%u: used for clock events\n",
 		 ch->index);
 	clockevents_register_device(ced);
@@ -996,6 +989,18 @@ static int sh_cmt_setup(struct sh_cmt_device *cmt, struct platform_device *pdev)
 	if (ret < 0)
 		goto err_clk_put;
 
+	/* Determine clock rate. */
+	ret = clk_enable(cmt->clk);
+	if (ret < 0)
+		goto err_clk_unprepare;
+
+	if (cmt->info->width == 16)
+		cmt->rate = clk_get_rate(cmt->clk) / 512;
+	else
+		cmt->rate = clk_get_rate(cmt->clk) / 8;
+
+	clk_disable(cmt->clk);
+
 	/* Map the memory resource(s). */
 	ret = sh_cmt_map_memory(cmt);
 	if (ret < 0)
-- 
2.11.1

[PATCH 2/6] clocksource: sh_tmu: compute rate before registration again

[Nicolai Stange]

With the upcoming NTP correction related rate adjustments to be implemented
in the clockevents core, the latter needs to get informed about every rate
change of a clockevent device made after its registration.

Currently, sh_tmu violates this requirement in that it registers its
clockevent device with a dummy rate and sets its final rate through
clockevents_config() called from its ->set_state_oneshot() and
->set_state_periodic() functions respectively.

This patch moves the setting of the clockevent device's rate to its
registration.

Note that there has been some back and forth regarding this question with
respect to the clocksource also provided by this driver:
  commit 66f49121ffa4 ("clocksource: sh_tmu: compute mult and shift before
                        registration")
moves the rate determination from the clocksource's ->enable() function to
before its registration. OTOH, the later
  commit 0aeac458d9eb ("clocksource: sh_tmu: __clocksource_updatefreq_hz()
                        update")
basically reverts this, saying
  "Without this patch the old code uses clocksource_register() together
   with a hack that assumes a never changing clock rate."

However, I checked all current sh_tmu users in arch/sh as well as in
arch/arm/mach-shmobile carefully and right now, none of them changes any
rate in any clock tree relevant to sh_tmu after their respective
time_init(). Since all sh_tmu instances are created after time_init(), none
of them should ever observe any clock rate changes.

What's more, both, a clocksource as well as a clockevent device, can
immediately get selected for use at their registration and thus, enabled
at this point already. So it's probably safer to assume a "never changing
clock rate" here.

- Move the struct sh_tmu_channel's ->rate member to struct sh_tmu_device:
  it's a property of the underlying clock which is in turn specific to
  the sh_tmu_device.
- Determine the ->rate value in sh_tmu_setup() at device probing rather
  than at first usage.
- Set the clockevent device's rate at its registration.
- Although not strictly necessary for the upcoming clockevent core changes,
  set the clocksource's rate at its registration for consistency.

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
---

Notes:
    For a detailed analysis of the current sh_tmu users, please see
    https://nicst.de/ced-clk-rate-change-analysis/sh_tmu-cgitted.html
    
    Compile-only tested on ARCH=sh and ARCH=arm.

 drivers/clocksource/sh_tmu.c | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/drivers/clocksource/sh_tmu.c b/drivers/clocksource/sh_tmu.c
index 1fbf2aadcfd4..31d881621e41 100644
--- a/drivers/clocksource/sh_tmu.c
+++ b/drivers/clocksource/sh_tmu.c
@@ -46,7 +46,6 @@ struct sh_tmu_channel {
 	void __iomem *base;
 	int irq;
 
-	unsigned long rate;
 	unsigned long periodic;
 	struct clock_event_device ced;
 	struct clocksource cs;
@@ -59,6 +58,7 @@ struct sh_tmu_device {
 
 	void __iomem *mapbase;
 	struct clk *clk;
+	unsigned long rate;
 
 	enum sh_tmu_model model;
 
@@ -165,7 +165,6 @@ static int __sh_tmu_enable(struct sh_tmu_channel *ch)
 	sh_tmu_write(ch, TCNT, 0xffffffff);
 
 	/* configure channel to parent clock / 4, irq off */
-	ch->rate = clk_get_rate(ch->tmu->clk) / 4;
 	sh_tmu_write(ch, TCR, TCR_TPSC_CLK4);
 
 	/* enable channel */
@@ -271,10 +270,8 @@ static int sh_tmu_clocksource_enable(struct clocksource *cs)
 		return 0;
 
 	ret = sh_tmu_enable(ch);
-	if (!ret) {
-		__clocksource_update_freq_hz(cs, ch->rate);
+	if (!ret)
 		ch->cs_enabled = true;
-	}
 
 	return ret;
 }
@@ -334,8 +331,7 @@ static int sh_tmu_register_clocksource(struct sh_tmu_channel *ch,
 	dev_info(&ch->tmu->pdev->dev, "ch%u: used as clock source\n",
 		 ch->index);
 
-	/* Register with dummy 1 Hz value, gets updated in ->enable() */
-	clocksource_register_hz(cs, 1);
+	clocksource_register_hz(cs, ch->tmu->rate);
 	return 0;
 }
 
@@ -346,14 +342,10 @@ static struct sh_tmu_channel *ced_to_sh_tmu(struct clock_event_device *ced)
 
 static void sh_tmu_clock_event_start(struct sh_tmu_channel *ch, int periodic)
 {
-	struct clock_event_device *ced = &ch->ced;
-
 	sh_tmu_enable(ch);
 
-	clockevents_config(ced, ch->rate);
-
 	if (periodic) {
-		ch->periodic = (ch->rate + HZ/2) / HZ;
+		ch->periodic = (ch->tmu->rate + HZ/2) / HZ;
 		sh_tmu_set_next(ch, ch->periodic, 1);
 	}
 }
@@ -435,7 +427,7 @@ static void sh_tmu_register_clockevent(struct sh_tmu_channel *ch,
 	dev_info(&ch->tmu->pdev->dev, "ch%u: used for clock events\n",
 		 ch->index);
 
-	clockevents_config_and_register(ced, 1, 0x300, 0xffffffff);
+	clockevents_config_and_register(ced, ch->tmu->rate, 0x300, 0xffffffff);
 
 	ret = request_irq(ch->irq, sh_tmu_interrupt,
 			  IRQF_TIMER | IRQF_IRQPOLL | IRQF_NOBALANCING,
@@ -561,6 +553,14 @@ static int sh_tmu_setup(struct sh_tmu_device *tmu, struct platform_device *pdev)
 	if (ret < 0)
 		goto err_clk_put;
 
+	/* Determine clock rate. */
+	ret = clk_enable(tmu->clk);
+	if (ret < 0)
+		goto err_clk_unprepare;
+
+	tmu->rate = clk_get_rate(tmu->clk) / 4;
+	clk_disable(tmu->clk);
+
 	/* Map the memory resource. */
 	ret = sh_tmu_map_memory(tmu);
 	if (ret < 0) {
-- 
2.11.1

[PATCH 3/6] clocksource: em_sti: split clock prepare and enable steps

[Nicolai Stange]

Currently, the em_sti driver prepares and enables the needed clock in
em_sti_enable(), potentially called through its clockevent device's
->set_state_oneshot().

However, the clk_prepare() step may sleep whereas tick_program_event() and
thus, ->set_state_oneshot(), can be called in atomic context.

Split the clk_prepare_enable() in em_sti_enable() into two steps:
- prepare the clock at device probing via clk_prepare()
- and enable it in em_sti_enable() via clk_enable().
Slightly reorder resource initialization in em_sti_probe() in order to
facilitate error handling in later patches.

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
---

Notes:
    Compile-only tested on ARCH=arm.

 drivers/clocksource/em_sti.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/clocksource/em_sti.c b/drivers/clocksource/em_sti.c
index aff87df07449..6c0955a92f24 100644
--- a/drivers/clocksource/em_sti.c
+++ b/drivers/clocksource/em_sti.c
@@ -78,7 +78,7 @@ static int em_sti_enable(struct em_sti_priv *p)
 	int ret;
 
 	/* enable clock */
-	ret = clk_prepare_enable(p->clk);
+	ret = clk_enable(p->clk);
 	if (ret) {
 		dev_err(&p->pdev->dev, "cannot enable clock\n");
 		return ret;
@@ -107,7 +107,7 @@ static void em_sti_disable(struct em_sti_priv *p)
 	em_sti_write(p, STI_INTENCLR, 3);
 
 	/* stop clock */
-	clk_disable_unprepare(p->clk);
+	clk_disable(p->clk);
 }
 
 static u64 em_sti_count(struct em_sti_priv *p)
@@ -303,6 +303,7 @@ static int em_sti_probe(struct platform_device *pdev)
 	struct em_sti_priv *p;
 	struct resource *res;
 	int irq;
+	int ret;
 
 	p = devm_kzalloc(&pdev->dev, sizeof(*p), GFP_KERNEL);
 	if (p == NULL)
@@ -323,6 +324,13 @@ static int em_sti_probe(struct platform_device *pdev)
 	if (IS_ERR(p->base))
 		return PTR_ERR(p->base);
 
+	if (devm_request_irq(&pdev->dev, irq, em_sti_interrupt,
+			     IRQF_TIMER | IRQF_IRQPOLL | IRQF_NOBALANCING,
+			     dev_name(&pdev->dev), p)) {
+		dev_err(&pdev->dev, "failed to request low IRQ\n");
+		return -ENOENT;
+	}
+
 	/* get hold of clock */
 	p->clk = devm_clk_get(&pdev->dev, "sclk");
 	if (IS_ERR(p->clk)) {
@@ -330,11 +338,10 @@ static int em_sti_probe(struct platform_device *pdev)
 		return PTR_ERR(p->clk);
 	}
 
-	if (devm_request_irq(&pdev->dev, irq, em_sti_interrupt,
-			     IRQF_TIMER | IRQF_IRQPOLL | IRQF_NOBALANCING,
-			     dev_name(&pdev->dev), p)) {
-		dev_err(&pdev->dev, "failed to request low IRQ\n");
-		return -ENOENT;
+	ret = clk_prepare(p->clk);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "cannot prepare clock\n");
+		return ret;
 	}
 
 	raw_spin_lock_init(&p->lock);
-- 
2.11.1

[PATCH 4/6] clocksource: em_sti: compute rate before registration

[Nicolai Stange]

With the upcoming NTP correction related rate adjustments to be implemented
in the clockevents core, the latter needs to get informed about every rate
change of a clockevent device made after its registration.

Currently, em_sti violates this requirement in that it registers its
clockevent device with a dummy rate and sets its final rate through
clockevents_config() called from its ->set_state_oneshot().

This patch moves the setting of the clockevent device's rate to its
registration.

I checked all current em_sti users in arch/arm/mach-shmobile and right now,
none of them changes any rate in any clock tree relevant to em_sti after
their respective time_init(). Since all em_sti instances are created after
time_init(), none of them should ever observe any clock rate changes.

- Determine the ->rate value in em_sti_probe() at device probing rather
  than at first usage.
- Set the clockevent device's rate at its registration.
- Although not strictly necessary for the upcoming clockevent core changes,
  set the clocksource's rate at its registration for consistency.

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
---

Notes:
    For a detailed analysis of the current em_sti users, please see
    https://nicst.de/ced-clk-rate-change-analysis/em_sti-cgitted.html
    
    Compile-only tested on ARCH=arm.

 drivers/clocksource/em_sti.c | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/drivers/clocksource/em_sti.c b/drivers/clocksource/em_sti.c
index 6c0955a92f24..bc48cbf6a795 100644
--- a/drivers/clocksource/em_sti.c
+++ b/drivers/clocksource/em_sti.c
@@ -84,9 +84,6 @@ static int em_sti_enable(struct em_sti_priv *p)
 		return ret;
 	}
 
-	/* configure channel, periodic mode and maximum timeout */
-	p->rate = clk_get_rate(p->clk);
-
 	/* reset the counter */
 	em_sti_write(p, STI_SET_H, 0x40000000);
 	em_sti_write(p, STI_SET_L, 0x00000000);
@@ -205,13 +202,9 @@ static u64 em_sti_clocksource_read(struct clocksource *cs)
 
 static int em_sti_clocksource_enable(struct clocksource *cs)
 {
-	int ret;
 	struct em_sti_priv *p = cs_to_em_sti(cs);
 
-	ret = em_sti_start(p, USER_CLOCKSOURCE);
-	if (!ret)
-		__clocksource_update_freq_hz(cs, p->rate);
-	return ret;
+	return em_sti_start(p, USER_CLOCKSOURCE);
 }
 
 static void em_sti_clocksource_disable(struct clocksource *cs)
@@ -240,8 +233,7 @@ static int em_sti_register_clocksource(struct em_sti_priv *p)
 
 	dev_info(&p->pdev->dev, "used as clock source\n");
 
-	/* Register with dummy 1 Hz value, gets updated in ->enable() */
-	clocksource_register_hz(cs, 1);
+	clocksource_register_hz(cs, p->rate);
 	return 0;
 }
 
@@ -263,7 +255,6 @@ static int em_sti_clock_event_set_oneshot(struct clock_event_device *ced)
 
 	dev_info(&p->pdev->dev, "used for oneshot clock events\n");
 	em_sti_start(p, USER_CLOCKEVENT);
-	clockevents_config(&p->ced, p->rate);
 	return 0;
 }
 
@@ -294,8 +285,7 @@ static void em_sti_register_clockevent(struct em_sti_priv *p)
 
 	dev_info(&p->pdev->dev, "used for clock events\n");
 
-	/* Register with dummy 1 Hz value, gets updated in ->set_state_oneshot() */
-	clockevents_config_and_register(ced, 1, 2, 0xffffffff);
+	clockevents_config_and_register(ced, p->rate, 2, 0xffffffff);
 }
 
 static int em_sti_probe(struct platform_device *pdev)
@@ -344,6 +334,15 @@ static int em_sti_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	ret = clk_enable(p->clk);
+	if (ret < 0) {
+		dev_err(&p->pdev->dev, "cannot enable clock\n");
+		clk_unprepare(p->clk);
+		return ret;
+	}
+	p->rate = clk_get_rate(p->clk);
+	clk_disable(p->clk);
+
 	raw_spin_lock_init(&p->lock);
 	em_sti_register_clockevent(p);
 	em_sti_register_clocksource(p);
-- 
2.11.1

[PATCH 5/6] clocksource: h8300_timer8: don't reset rate in ->set_state_oneshot()

[Nicolai Stange]

With the upcoming NTP correction related rate adjustments to be implemented
in the clockevents core, the latter needs to get informed about every rate
change of a clockevent device made after its registration.

Currently, h8300_timer8 violates this requirement in that it registers its
clockevent device with the correct rate, but resets its ->mult and ->rate
values in timer8_clock_event_start(), called from its ->set_state_oneshot()
function.

It seems like
  commit 4633f4cac85a ("clocksource/drivers/h8300: Cleanup startup and
                        remove module code."),
which introduced the rate initialization at registration, missed to remove
the manual setting of ->mult and ->shift from timer8_clock_event_start().

Purge the setting of ->mult, ->shift, ->min_delta_ns and ->max_delta_ns
from timer8_clock_event_start().

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
---

Notes:
    Compile-only tested on ARCH=h8300.

 drivers/clocksource/h8300_timer8.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/drivers/clocksource/h8300_timer8.c b/drivers/clocksource/h8300_timer8.c
index 546bb180f5a4..804c489531d6 100644
--- a/drivers/clocksource/h8300_timer8.c
+++ b/drivers/clocksource/h8300_timer8.c
@@ -101,15 +101,7 @@ static inline struct timer8_priv *ced_to_priv(struct clock_event_device *ced)
 
 static void timer8_clock_event_start(struct timer8_priv *p, unsigned long delta)
 {
-	struct clock_event_device *ced = &p->ced;
-
 	timer8_start(p);
-
-	ced->shift = 32;
-	ced->mult = div_sc(p->rate, NSEC_PER_SEC, ced->shift);
-	ced->max_delta_ns = clockevent_delta2ns(0xffff, ced);
-	ced->min_delta_ns = clockevent_delta2ns(0x0001, ced);
-
 	timer8_set_next(p, delta);
 }
 
-- 
2.11.1

[PATCH 6/6] clockevents: make clockevents_config() static

[Nicolai Stange]

A clockevent device's rate should be configured before or at registration
and changed afterwards through clockevents_update_freq() only.

For the configuration at registration, we already have
clockevents_config_and_register().

Right now, there are no clockevents_config() users outside of the
clockevents core.

To mitigiate the risk of drivers errorneously reconfiguring their rates
through clockevents_config() *after* device registration, make
clockevents_config() static.

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
---
 include/linux/clockchips.h | 1 -
 kernel/time/clockevents.c  | 2 +-
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h
index 0d442e34c349..a116926598fd 100644
--- a/include/linux/clockchips.h
+++ b/include/linux/clockchips.h
@@ -182,7 +182,6 @@ extern u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *e
 extern void clockevents_register_device(struct clock_event_device *dev);
 extern int clockevents_unbind_device(struct clock_event_device *ced, int cpu);
 
-extern void clockevents_config(struct clock_event_device *dev, u32 freq);
 extern void clockevents_config_and_register(struct clock_event_device *dev,
 					    u32 freq, unsigned long min_delta,
 					    unsigned long max_delta);
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 97ac0951f164..4237e0744e26 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -468,7 +468,7 @@ void clockevents_register_device(struct clock_event_device *dev)
 }
 EXPORT_SYMBOL_GPL(clockevents_register_device);
 
-void clockevents_config(struct clock_event_device *dev, u32 freq)
+static void clockevents_config(struct clock_event_device *dev, u32 freq)
 {
 	u64 sec;
 
-- 
2.11.1

Re: [PATCH 1/6] clocksource: sh_cmt: compute rate before registration again

[John Stultz]

On Mon, Feb 6, 2017 at 1:11 PM, Nicolai Stange <nicstange@gmail.com> wrote:
> With the upcoming NTP correction related rate adjustments to be implemented
> in the clockevents core, the latter needs to get informed about every rate
> change of a clockevent device made after its registration.
>
> Currently, sh_cmt violates this requirement in that it registers its
> clockevent device with a dummy rate and sets its final ->mult and ->shift
> values from its ->set_state_oneshot() and ->set_state_periodic() functions
> respectively.
>
> This patch moves the setting of the clockevent device's ->mult and ->shift
> values to before its registration.
>
> Note that there has been some back and forth regarding this question with
> respect to the clocksource also provided by this driver:
>   commit f4d7c3565c16 ("clocksource: sh_cmt: compute mult and shift before
>                         registration")
> moves the rate determination from the clocksource's ->enable() function to
> before its registration. OTOH, the later
>   commit 3593f5fe40a1 ("clocksource: sh_cmt: __clocksource_updatefreq_hz()
>                         update")
> basically reverts this, saying
>   "Without this patch the old code uses clocksource_register() together
>    with a hack that assumes a never changing clock rate."
>
> However, I checked all current sh_cmt users in arch/sh as well as in
> arch/arm/mach-shmobile carefully and right now, none of them changes any
> rate in any clock tree relevant to sh_cmt after their respective
> time_init(). Since all sh_cmt instances are created after time_init(), none
> of them should ever observe any clock rate changes.
>
> What's more, both, a clocksource as well as a clockevent device, can
> immediately get selected for use at their registration and thus, enabled
> at this point already. So it's probably safer to assume a "never changing
> clock rate" here.
>
> - Move the struct sh_cmt_channel's ->rate member to struct sh_cmt_device:
>   it's a property of the underlying clock which is in turn specific to
>   the sh_cmt_device.
> - Determine the ->rate value in sh_cmt_setup() at device probing rather
>   than at first usage.
> - Set the clockevent device's ->mult and ->shift values right before its
>   registration.
> - Although not strictly necessary for the upcoming clockevent core changes,
>   set the clocksource's rate at its registration for consistency.

Magnus: Do you have any objection to the above?  I know we reworked
this a few times in the past.

thanks
-john