[v4,2/5] ARC: clocksource: DT based probe
diff mbox

Message ID 1460547605-26184-3-git-send-email-vgupta@synopsys.com
State New
Headers show

Commit Message

Vineet Gupta April 13, 2016, 11:40 a.m. UTC
- Remove explicit clocksource setup and let it be done by OF framework
  by defining CLOCKSOURCE_OF_DECLARE() for various timers

- This allows multiple clocksources to be potentially registered
  simultaneouly: previously we could only do one - as all of them had
  same arc_counter_setup() routine for registration

- Setup routines also ensure that the underlying timer actually exists.

- Remove some of the panic() calls if underlying timer is NOT detected as
  fallback clocksource might still be available
  1. If GRFC doesn't exist, jiffies clocksource gets registered anyways
  2. if RTC doesn't exist, TIMER1 can take over (as it is always
     present)

Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
 arch/arc/kernel/mcip.c  |   4 +-
 arch/arc/kernel/setup.c |   3 --
 arch/arc/kernel/time.c  | 124 +++++++++++++++++++++++++++---------------------
 3 files changed, 72 insertions(+), 59 deletions(-)

Comments

Marc Zyngier April 13, 2016, 4:22 p.m. UTC | #1
On 13/04/16 12:40, Vineet Gupta wrote:
> - Remove explicit clocksource setup and let it be done by OF framework
>   by defining CLOCKSOURCE_OF_DECLARE() for various timers
> 
> - This allows multiple clocksources to be potentially registered
>   simultaneouly: previously we could only do one - as all of them had
>   same arc_counter_setup() routine for registration
> 
> - Setup routines also ensure that the underlying timer actually exists.
> 
> - Remove some of the panic() calls if underlying timer is NOT detected as
>   fallback clocksource might still be available
>   1. If GRFC doesn't exist, jiffies clocksource gets registered anyways
>   2. if RTC doesn't exist, TIMER1 can take over (as it is always
>      present)
> 
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
> ---
>  arch/arc/kernel/mcip.c  |   4 +-
>  arch/arc/kernel/setup.c |   3 --
>  arch/arc/kernel/time.c  | 124 +++++++++++++++++++++++++++---------------------
>  3 files changed, 72 insertions(+), 59 deletions(-)
> 
> diff --git a/arch/arc/kernel/mcip.c b/arch/arc/kernel/mcip.c
> index c41c364b926c..262d9c3771e6 100644
> --- a/arch/arc/kernel/mcip.c
> +++ b/arch/arc/kernel/mcip.c
> @@ -116,15 +116,13 @@ static void mcip_probe_n_setup(void)
>  		IS_AVAIL1(mp.dbg, "DEBUG "),
>  		IS_AVAIL1(mp.gfrc, "GFRC"));
>  
> +	cpuinfo_arc700[0].extn.gfrc = mp.gfrc;
>  	idu_detected = mp.idu;
>  
>  	if (mp.dbg) {
>  		__mcip_cmd_data(CMD_DEBUG_SET_SELECT, 0, 0xf);
>  		__mcip_cmd_data(CMD_DEBUG_SET_MASK, 0xf, 0xf);
>  	}
> -
> -	if (IS_ENABLED(CONFIG_ARC_HAS_GFRC) && !mp.gfrc)
> -		panic("kernel trying to use non-existent GFRC\n");
>  }
>  
>  struct plat_smp_ops plat_smp_ops = {
> diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c
> index 507ec523112a..91f79fa447bc 100644
> --- a/arch/arc/kernel/setup.c
> +++ b/arch/arc/kernel/setup.c
> @@ -313,9 +313,6 @@ static void arc_chk_core_config(void)
>  	if (!cpu->extn.timer1)
>  		panic("Timer1 is not present!\n");
>  
> -	if (IS_ENABLED(CONFIG_ARC_HAS_RTC) && !cpu->extn.rtc)
> -		panic("RTC is not present\n");
> -
>  #ifdef CONFIG_ARC_HAS_DCCM
>  	/*
>  	 * DCCM can be arbit placed in hardware.
> diff --git a/arch/arc/kernel/time.c b/arch/arc/kernel/time.c
> index 693545df9827..72f023440739 100644
> --- a/arch/arc/kernel/time.c
> +++ b/arch/arc/kernel/time.c
> @@ -77,12 +77,7 @@ static void noinline arc_get_timer_clk(struct device_node *node)
>  
>  #ifdef CONFIG_ARC_HAS_GFRC
>  
> -static int arc_counter_setup(void)
> -{
> -	return 1;
> -}
> -
> -static cycle_t arc_counter_read(struct clocksource *cs)
> +static cycle_t arc_read_gfrc(struct clocksource *cs)
>  {
>  	unsigned long flags;
>  	union {
> @@ -107,15 +102,28 @@ static cycle_t arc_counter_read(struct clocksource *cs)
>  	return stamp.full;
>  }
>  
> -static struct clocksource arc_counter = {
> +static struct clocksource arc_counter_gfrc = {
>  	.name   = "ARConnect GFRC",
>  	.rating = 400,
> -	.read   = arc_counter_read,
> +	.read   = arc_read_gfrc,
>  	.mask   = CLOCKSOURCE_MASK(64),
>  	.flags  = CLOCK_SOURCE_IS_CONTINUOUS,
>  };
>  
> -#else
> +static void __init arc_cs_setup_gfrc(struct device_node *node)
> +{
> +	int exists = cpuinfo_arc700[0].extn.gfrc;
> +
> +	if (WARN(!exists, "Global-64-bit-Ctr clocksource not detected"))
> +		return;
> +
> +	arc_get_timer_clk(node);
> +
> +	clocksource_register_hz(&arc_counter_gfrc, arc_timer_freq);
> +}
> +CLOCKSOURCE_OF_DECLARE(arc_gfrc, "snps,archs-timer-gfrc", arc_cs_setup_gfrc);
> +
> +#endif
>  
>  #ifdef CONFIG_ARC_HAS_RTC
>  
> @@ -123,15 +131,7 @@ static struct clocksource arc_counter = {
>  #define AUX_RTC_LOW	0x104
>  #define AUX_RTC_HIGH	0x105
>  
> -int arc_counter_setup(void)
> -{
> -	write_aux_reg(AUX_RTC_CTRL, 1);
> -
> -	/* Not usable in SMP */
> -	return !IS_ENABLED(CONFIG_SMP);
> -}
> -
> -static cycle_t arc_counter_read(struct clocksource *cs)
> +static cycle_t arc_read_rtc(struct clocksource *cs)
>  {
>  	unsigned long status;
>  	union {
> @@ -155,44 +155,66 @@ static cycle_t arc_counter_read(struct clocksource *cs)
>  	return stamp.full;
>  }
>  
> -static struct clocksource arc_counter = {
> +static struct clocksource arc_counter_rtc = {
>  	.name   = "ARCv2 RTC",
>  	.rating = 350,
> -	.read   = arc_counter_read,
> +	.read   = arc_read_rtc,
>  	.mask   = CLOCKSOURCE_MASK(64),
>  	.flags  = CLOCK_SOURCE_IS_CONTINUOUS,
>  };
>  
> -#else /* !CONFIG_ARC_HAS_RTC */
> -
> -/*
> - * set 32bit TIMER1 to keep counting monotonically and wraparound
> - */
> -int arc_counter_setup(void)
> +static void __init arc_cs_setup_rtc(struct device_node *node)
>  {
> -	write_aux_reg(ARC_REG_TIMER1_LIMIT, ARC_TIMER_MAX);
> -	write_aux_reg(ARC_REG_TIMER1_CNT, 0);
> -	write_aux_reg(ARC_REG_TIMER1_CTRL, TIMER_CTRL_NH);
> +	int exists = cpuinfo_arc700[smp_processor_id()].extn.rtc;
> +
> +	if (WARN(!exists, "Local-64-bit-Ctr clocksource not detected"))
> +		return;
> +
> +	/* Local to CPU hence not usable in SMP */
> +	if (WARN(IS_ENABLED(CONFIG_SMP), "Local-64-bit-Ctr not usable in SMP"))
> +		return;

Sorry if this outlines my lack of understanding of the ARC architecture,
but what makes per-cpu timer unsuitable for SMP? I'd have thought that
it was actually what you wanted...

Thanks,

	M.
Vineet Gupta April 14, 2016, 9:26 a.m. UTC | #2
On Wednesday 13 April 2016 09:52 PM, Marc Zyngier wrote:
>> -int arc_counter_setup(void)
>> > +static void __init arc_cs_setup_rtc(struct device_node *node)
>> >  {
>> > -	write_aux_reg(ARC_REG_TIMER1_LIMIT, ARC_TIMER_MAX);
>> > -	write_aux_reg(ARC_REG_TIMER1_CNT, 0);
>> > -	write_aux_reg(ARC_REG_TIMER1_CTRL, TIMER_CTRL_NH);
>> > +	int exists = cpuinfo_arc700[smp_processor_id()].extn.rtc;
>> > +
>> > +	if (WARN(!exists, "Local-64-bit-Ctr clocksource not detected"))
>> > +		return;
>> > +
>> > +	/* Local to CPU hence not usable in SMP */
>> > +	if (WARN(IS_ENABLED(CONFIG_SMP), "Local-64-bit-Ctr not usable in SMP"))
>> > +		return;
> Sorry if this outlines my lack of understanding of the ARC architecture,
> but what makes per-cpu timer unsuitable for SMP? I'd have thought that
> it was actually what you wanted...

This is clocksource, not clockevent. cs needs to synchronized across all cores so
that concurrent gtod call from threads on different cores gives you similar
values. This obviously is not true for the local RTC hardware timer.
Marc Zyngier April 14, 2016, 9:32 a.m. UTC | #3
On 14/04/16 10:26, Vineet Gupta wrote:
> On Wednesday 13 April 2016 09:52 PM, Marc Zyngier wrote:
>>> -int arc_counter_setup(void)
>>>> +static void __init arc_cs_setup_rtc(struct device_node *node)
>>>>  {
>>>> -	write_aux_reg(ARC_REG_TIMER1_LIMIT, ARC_TIMER_MAX);
>>>> -	write_aux_reg(ARC_REG_TIMER1_CNT, 0);
>>>> -	write_aux_reg(ARC_REG_TIMER1_CTRL, TIMER_CTRL_NH);
>>>> +	int exists = cpuinfo_arc700[smp_processor_id()].extn.rtc;
>>>> +
>>>> +	if (WARN(!exists, "Local-64-bit-Ctr clocksource not detected"))
>>>> +		return;
>>>> +
>>>> +	/* Local to CPU hence not usable in SMP */
>>>> +	if (WARN(IS_ENABLED(CONFIG_SMP), "Local-64-bit-Ctr not usable in SMP"))
>>>> +		return;
>> Sorry if this outlines my lack of understanding of the ARC architecture,
>> but what makes per-cpu timer unsuitable for SMP? I'd have thought that
>> it was actually what you wanted...
> 
> This is clocksource, not clockevent. cs needs to synchronized across all cores so
> that concurrent gtod call from threads on different cores gives you similar
> values. This obviously is not true for the local RTC hardware timer.

Unsynchronized counters on SMP HW, who would have thought! ;-) I guess
each and every architecture has to repeat the same mistakes.

Thanks for shedding some light on it.

	M.
Vineet Gupta April 14, 2016, 9:36 a.m. UTC | #4
On Thursday 14 April 2016 03:02 PM, Marc Zyngier wrote:
>> This is clocksource, not clockevent. cs needs to synchronized across all cores so
>> > that concurrent gtod call from threads on different cores gives you similar
>> > values. This obviously is not true for the local RTC hardware timer.
> Unsynchronized counters on SMP HW, who would have thought! ;-) I guess
> each and every architecture has to repeat the same mistakes.

Not really - hardware wise the SMP support is pretty recent and before that we
only had UP cores. So transition from 32 TIMER1 to 64 bit RTC was only a natural
progression in improvements and in theory SoC guys throw in this local timer into
the config. We just prevent SMP linux from using it.

Patch
diff mbox

diff --git a/arch/arc/kernel/mcip.c b/arch/arc/kernel/mcip.c
index c41c364b926c..262d9c3771e6 100644
--- a/arch/arc/kernel/mcip.c
+++ b/arch/arc/kernel/mcip.c
@@ -116,15 +116,13 @@  static void mcip_probe_n_setup(void)
 		IS_AVAIL1(mp.dbg, "DEBUG "),
 		IS_AVAIL1(mp.gfrc, "GFRC"));
 
+	cpuinfo_arc700[0].extn.gfrc = mp.gfrc;
 	idu_detected = mp.idu;
 
 	if (mp.dbg) {
 		__mcip_cmd_data(CMD_DEBUG_SET_SELECT, 0, 0xf);
 		__mcip_cmd_data(CMD_DEBUG_SET_MASK, 0xf, 0xf);
 	}
-
-	if (IS_ENABLED(CONFIG_ARC_HAS_GFRC) && !mp.gfrc)
-		panic("kernel trying to use non-existent GFRC\n");
 }
 
 struct plat_smp_ops plat_smp_ops = {
diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c
index 507ec523112a..91f79fa447bc 100644
--- a/arch/arc/kernel/setup.c
+++ b/arch/arc/kernel/setup.c
@@ -313,9 +313,6 @@  static void arc_chk_core_config(void)
 	if (!cpu->extn.timer1)
 		panic("Timer1 is not present!\n");
 
-	if (IS_ENABLED(CONFIG_ARC_HAS_RTC) && !cpu->extn.rtc)
-		panic("RTC is not present\n");
-
 #ifdef CONFIG_ARC_HAS_DCCM
 	/*
 	 * DCCM can be arbit placed in hardware.
diff --git a/arch/arc/kernel/time.c b/arch/arc/kernel/time.c
index 693545df9827..72f023440739 100644
--- a/arch/arc/kernel/time.c
+++ b/arch/arc/kernel/time.c
@@ -77,12 +77,7 @@  static void noinline arc_get_timer_clk(struct device_node *node)
 
 #ifdef CONFIG_ARC_HAS_GFRC
 
-static int arc_counter_setup(void)
-{
-	return 1;
-}
-
-static cycle_t arc_counter_read(struct clocksource *cs)
+static cycle_t arc_read_gfrc(struct clocksource *cs)
 {
 	unsigned long flags;
 	union {
@@ -107,15 +102,28 @@  static cycle_t arc_counter_read(struct clocksource *cs)
 	return stamp.full;
 }
 
-static struct clocksource arc_counter = {
+static struct clocksource arc_counter_gfrc = {
 	.name   = "ARConnect GFRC",
 	.rating = 400,
-	.read   = arc_counter_read,
+	.read   = arc_read_gfrc,
 	.mask   = CLOCKSOURCE_MASK(64),
 	.flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
-#else
+static void __init arc_cs_setup_gfrc(struct device_node *node)
+{
+	int exists = cpuinfo_arc700[0].extn.gfrc;
+
+	if (WARN(!exists, "Global-64-bit-Ctr clocksource not detected"))
+		return;
+
+	arc_get_timer_clk(node);
+
+	clocksource_register_hz(&arc_counter_gfrc, arc_timer_freq);
+}
+CLOCKSOURCE_OF_DECLARE(arc_gfrc, "snps,archs-timer-gfrc", arc_cs_setup_gfrc);
+
+#endif
 
 #ifdef CONFIG_ARC_HAS_RTC
 
@@ -123,15 +131,7 @@  static struct clocksource arc_counter = {
 #define AUX_RTC_LOW	0x104
 #define AUX_RTC_HIGH	0x105
 
-int arc_counter_setup(void)
-{
-	write_aux_reg(AUX_RTC_CTRL, 1);
-
-	/* Not usable in SMP */
-	return !IS_ENABLED(CONFIG_SMP);
-}
-
-static cycle_t arc_counter_read(struct clocksource *cs)
+static cycle_t arc_read_rtc(struct clocksource *cs)
 {
 	unsigned long status;
 	union {
@@ -155,44 +155,66 @@  static cycle_t arc_counter_read(struct clocksource *cs)
 	return stamp.full;
 }
 
-static struct clocksource arc_counter = {
+static struct clocksource arc_counter_rtc = {
 	.name   = "ARCv2 RTC",
 	.rating = 350,
-	.read   = arc_counter_read,
+	.read   = arc_read_rtc,
 	.mask   = CLOCKSOURCE_MASK(64),
 	.flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
-#else /* !CONFIG_ARC_HAS_RTC */
-
-/*
- * set 32bit TIMER1 to keep counting monotonically and wraparound
- */
-int arc_counter_setup(void)
+static void __init arc_cs_setup_rtc(struct device_node *node)
 {
-	write_aux_reg(ARC_REG_TIMER1_LIMIT, ARC_TIMER_MAX);
-	write_aux_reg(ARC_REG_TIMER1_CNT, 0);
-	write_aux_reg(ARC_REG_TIMER1_CTRL, TIMER_CTRL_NH);
+	int exists = cpuinfo_arc700[smp_processor_id()].extn.rtc;
+
+	if (WARN(!exists, "Local-64-bit-Ctr clocksource not detected"))
+		return;
+
+	/* Local to CPU hence not usable in SMP */
+	if (WARN(IS_ENABLED(CONFIG_SMP), "Local-64-bit-Ctr not usable in SMP"))
+		return;
+
+	arc_get_timer_clk(node);
 
-	/* Not usable in SMP */
-	return !IS_ENABLED(CONFIG_SMP);
+	write_aux_reg(AUX_RTC_CTRL, 1);
+
+	clocksource_register_hz(&arc_counter_rtc, arc_timer_freq);
 }
+CLOCKSOURCE_OF_DECLARE(arc_rtc, "snps,archs-timer-rtc", arc_cs_setup_rtc);
+
+#endif
+
+/*
+ * 32bit TIMER1 to keep counting monotonically and wraparound
+ */
 
-static cycle_t arc_counter_read(struct clocksource *cs)
+static cycle_t arc_read_timer1(struct clocksource *cs)
 {
 	return (cycle_t) read_aux_reg(ARC_REG_TIMER1_CNT);
 }
 
-static struct clocksource arc_counter = {
+static struct clocksource arc_counter_timer1 = {
 	.name   = "ARC Timer1",
 	.rating = 300,
-	.read   = arc_counter_read,
+	.read   = arc_read_timer1,
 	.mask   = CLOCKSOURCE_MASK(32),
 	.flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
-#endif
-#endif
+static void __init arc_cs_setup_timer1(struct device_node *node)
+{
+	/* Local to CPU hence not usable in SMP */
+	if (IS_ENABLED(CONFIG_SMP))
+		return;
+
+	arc_get_timer_clk(node);
+
+	write_aux_reg(ARC_REG_TIMER1_LIMIT, ARC_TIMER_MAX);
+	write_aux_reg(ARC_REG_TIMER1_CNT, 0);
+	write_aux_reg(ARC_REG_TIMER1_CTRL, TIMER_CTRL_NH);
+
+	clocksource_register_hz(&arc_counter_timer1, arc_timer_freq);
+}
 
 /********** Clock Event Device *********/
 
@@ -312,29 +334,25 @@  static void __init arc_clockevent_setup(struct device_node *node)
 
 	enable_percpu_irq(arc_timer_irq, 0);
 }
-CLOCKSOURCE_OF_DECLARE(arc_clkevt, "snps,arc-timer", arc_clockevent_setup);
+
+static void __init arc_of_timer_init(struct device_node *np)
+{
+	static int init_count = 0;
+
+	if (!init_count) {
+		init_count = 1;
+		arc_clockevent_setup(np);
+	} else {
+		arc_cs_setup_timer1(np);
+	}
+}
+CLOCKSOURCE_OF_DECLARE(arc_clkevt, "snps,arc-timer", arc_of_timer_init);
 
 /*
  * Called from start_kernel() - boot CPU only
- *
- * -Sets up h/w timers as applicable on boot cpu
- * -Also sets up any global state needed for timer subsystem:
- *    - for "counting" timer, registers a clocksource, usable across CPUs
- *      (provided that underlying counter h/w is synchronized across cores)
  */
 void __init time_init(void)
 {
 	of_clk_init(NULL);
 	clocksource_probe();
-
-	/*
-	 * sets up the timekeeping free-flowing counter which also returns
-	 * whether the counter is usable as clocksource
-	 */
-	if (arc_counter_setup())
-		/*
-		 * CLK upto 4.29 GHz can be safely represented in 32 bits
-		 * because Max 32 bit number is 4,294,967,295
-		 */
-		clocksource_register_hz(&arc_counter, arc_timer_freq);
 }