[PATCH 4/4] ARM: ks8695: convert to generic time and clocksource

Old platforms using ancient gettimeoffset() and other arcane
APIs are standing in the way of cleaning up the ARM kernel.

This is an attempt at blind-coding a generic time and clocksource
driver for the platform by way of a datasheet and looking at the
old code, it'd be great if someone who is actually using this
machine could test it.

If noone volunteers to do this I will instead propose a patch
deleting the machine altogether.

Signed-off-by: Linus Walleij <redacted>
---
 arch/arm/Kconfig            |    3 +-
 arch/arm/mach-ks8695/time.c |  123 ++++++++++++++++++++++++++++++-------------
 2 files changed, 88 insertions(+), 38 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index c5f9ae5..181b697 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig

@@ -652,8 +652,9 @@ config ARCH_KS8695
 	bool "Micrel/Kendin KS8695"
 	select CPU_ARM922T
 	select ARCH_REQUIRE_GPIOLIB
-	select ARCH_USES_GETTIMEOFFSET
 	select NEED_MACH_MEMORY_H
+	select CLKSRC_MMIO
+	select GENERIC_CLOCKEVENTS
 	help
 	  Support for Micrel/Kendin KS8695 "Centaur" (ARM922T) based
 	  System-on-Chip devices.

diff --git a/arch/arm/mach-ks8695/time.c b/arch/arm/mach-ks8695/time.c
index 6974c23..1a933f1 100644
--- a/arch/arm/mach-ks8695/time.c
+++ b/arch/arm/mach-ks8695/time.c

@@ -25,6 +25,8 @@
 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/io.h>
+#include <linux/clockchips.h>
+#include <linux/clocksource.h>
 
 #include <asm/mach/time.h>
 #include <asm/system_misc.h>

@@ -53,44 +55,68 @@
 /* Timer0 Timeout Counter Register */
 #define T0TC_WATCHDOG		(0xff)		/* Enable watchdog mode */
 
-/*
- * Returns number of ms since last clock interrupt.  Note that interrupts
- * will have been disabled by do_gettimeoffset()
- */
-static unsigned long ks8695_gettimeoffset (void)
+static void ks8695_set_mode(enum clock_event_mode mode,
+			    struct clock_event_device *evt)
 {
-	unsigned long elapsed, tick2, intpending;
+	if (mode == CLOCK_EVT_FEAT_PERIODIC) {
+		u32 rate = DIV_ROUND_CLOSEST(KS8695_CLOCK_RATE, HZ);
+		u32 half = DIV_ROUND_CLOSEST(rate, 2);
+		u32 tmcon;
+
+		/* Disable timer 1 */
+		tmcon = readl_relaxed(KS8695_TMR_VA + KS8695_TMCON);
+		tmcon &= TMCON_T1EN;
+		writel_relaxed(tmcon, KS8695_TMR_VA + KS8695_TMCON);
+
+		/* Both registers need to count down */
+		writel_relaxed(half, KS8695_TMR_VA + KS8695_T1TC);
+		writel_relaxed(half, KS8695_TMR_VA + KS8695_T1PD);
+
+		/* Re-enable timer1 */
+		tmcon |= TMCON_T1EN;
+		writel_relaxed(tmcon, KS8695_TMR_VA + KS8695_TMCON);
+	}
+}
 
-	/*
-	 * Get the current number of ticks.  Note that there is a race
-	 * condition between us reading the timer and checking for an
-	 * interrupt.  We solve this by ensuring that the counter has not
-	 * reloaded between our two reads.
-	 */
-	elapsed = readl_relaxed(KS8695_TMR_VA + KS8695_T1TC) + readl_relaxed(KS8695_TMR_VA + KS8695_T1PD);
-	do {
-		tick2 = elapsed;
-		intpending = readl_relaxed(KS8695_IRQ_VA + KS8695_INTST) & (1 << KS8695_IRQ_TIMER1);
-		elapsed = readl_relaxed(KS8695_TMR_VA + KS8695_T1TC) + readl_relaxed(KS8695_TMR_VA + KS8695_T1PD);
-	} while (elapsed > tick2);
-
-	/* Convert to number of ticks expired (not remaining) */
-	elapsed = (CLOCK_TICK_RATE / HZ) - elapsed;
-
-	/* Is interrupt pending?  If so, then timer has been reloaded already. */
-	if (intpending)
-		elapsed += (CLOCK_TICK_RATE / HZ);
-
-	/* Convert ticks to usecs */
-	return (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH;
+static int ks8695_set_next_event(unsigned long cycles,
+				 struct clock_event_device *evt)
+
+{
+	u32 half = DIV_ROUND_CLOSEST(cycles, 2);
+	u32 tmcon;
+
+	/* Disable timer 1 */
+	tmcon = readl_relaxed(KS8695_TMR_VA + KS8695_TMCON);
+	tmcon &= TMCON_T1EN;
+	writel_relaxed(tmcon, KS8695_TMR_VA + KS8695_TMCON);
+
+	/* Both registers need to count down */
+	writel_relaxed(half, KS8695_TMR_VA + KS8695_T1TC);
+	writel_relaxed(half, KS8695_TMR_VA + KS8695_T1PD);
+
+	/* Re-enable timer1 */
+	tmcon |= TMCON_T1EN;
+	writel_relaxed(tmcon, KS8695_TMR_VA + KS8695_TMCON);
+
+	return 0;
 }
 
+static struct clock_event_device clockevent_ks8695 = {
+	.name		= "ks8695_t1tc",
+	.rating		= 300, /* Reasonably fast and accurate clock event */
+	.features	= CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC,
+	.set_next_event	= ks8695_set_next_event,
+	.set_mode	= ks8695_set_mode,
+};
+
 /*
  * IRQ handler for the timer.
  */
 static irqreturn_t ks8695_timer_interrupt(int irq, void *dev_id)
 {
-	timer_tick();
+	struct clock_event_device *evt = &clockevent_ks8695;
+
+	evt->event_handler(evt);
 	return IRQ_HANDLED;
 }
 

@@ -102,18 +128,42 @@ static struct irqaction ks8695_timer_irq = {
 
 static void ks8695_timer_setup(void)
 {
-	unsigned long tmout = CLOCK_TICK_RATE / HZ;
 	unsigned long tmcon;
 
-	/* disable timer1 */
+	/* Disable timer 0 and 1 */
 	tmcon = readl_relaxed(KS8695_TMR_VA + KS8695_TMCON);
-	writel_relaxed(tmcon & ~TMCON_T1EN, KS8695_TMR_VA + KS8695_TMCON);
+	tmcon &= TMCON_T0EN;
+	tmcon &= TMCON_T1EN;
+	writel_relaxed(tmcon, KS8695_TMR_VA + KS8695_TMCON);
 
-	writel_relaxed(tmout / 2, KS8695_TMR_VA + KS8695_T1TC);
-	writel_relaxed(tmout / 2, KS8695_TMR_VA + KS8695_T1PD);
+	/*
+	 * Set up timer 0 to loop indefinately, count 32 bits with TOUT0
+	 * set to zero, then 1 bit with TOUT0 set to 1. The reason we are doing
+	 * this is that it's not allowed to set either register to 0, then the
+	 * behaviour is "unpredictable". This injects a faulty pulse every
+	 * 2^32-1 cycles but we can surely live with that rather than
+	 * complicating the code.
+	 */
+	writel_relaxed(0xFFFFFFFFU, KS8695_TMR_VA + KS8695_T0TC);
+	writel_relaxed(1, KS8695_TMR_VA + KS8695_T0PD);
+	/* Start timer 0 */
+	tmcon |= TMCON_T0EN;
+	writel_relaxed(tmcon, KS8695_TMR_VA + KS8695_TMCON);
+	/* Use timer 0 as clocksource */
+	if (clocksource_mmio_init((void *) KS8695_TMR_VA + KS8695_T0TC,
+			"ks8695_t0tc", KS8695_CLOCK_RATE, 300, 32,
+			clocksource_mmio_readl_up))
+		pr_err("timer: failed to initialize KS8695 clock source\n");
 
-	/* re-enable timer1 */
-	writel_relaxed(tmcon | TMCON_T1EN, KS8695_TMR_VA + KS8695_TMCON);
+	/*
+	 * Use timer 1 to fire IRQs on the timeline, only support one-shot
+	 * mode and the system will take care of the rest. Minimum 2 cycles
+	 * (one on each counter) maximum 2*2^32, but the API will only
+	 * accept up to a 32bit full word (0xFFFFFFFFU).
+	 */
+	clockevents_config_and_register(&clockevent_ks8695,
+					KS8695_CLOCK_RATE, 2,
+					0xFFFFFFFFU);
 }
 
 static void __init ks8695_timer_init (void)

@@ -126,7 +176,6 @@ static void __init ks8695_timer_init (void)
 
 struct sys_timer ks8695_timer = {
 	.init		= ks8695_timer_init,
-	.offset		= ks8695_gettimeoffset,
 };
 
 void ks8695_restart(char mode, const char *cmd)

-- 
1.7.7.6

Hi Linus,

On 08/30/2012 04:27 AM, Linus Walleij wrote:

Old platforms using ancient gettimeoffset() and other arcane
APIs are standing in the way of cleaning up the ARM kernel.

This is an attempt at blind-coding a generic time and clocksource
driver for the platform by way of a datasheet and looking at the
old code, it'd be great if someone who is actually using this
machine could test it.

Ok, tested on a KS8695 based machine. Boots and runs, obviously
clock is basically working. But 'date' never shows the time
increasing:

   # date
   Thu Jan  1 00:00:00 UTC 1970
   # date
   Thu Jan  1 00:00:00 UTC 1970
   # date
   Thu Jan  1 00:00:00 UTC 1970
   #

And yes, that did work before applying this patch :-)

Regards
Greg

-- 
------------------------------------------------------------------------
Greg Ungerer  --  Principal Engineer        EMAIL:     gerg at snapgear.com
SnapGear Group, McAfee                      PHONE:       +61 7 3435 2888
8 Gardner Close,                            FAX:         +61 7 3891 3630
Milton, QLD, 4064, Australia                WEB: http://www.SnapGear.com

On Fri, Aug 31, 2012 at 8:20 AM, Greg Ungerer [off-list ref] wrote:

Ok, tested on a KS8695 based machine. Boots and runs, obviously
clock is basically working. But 'date' never shows the time
increasing:

  # date
  Thu Jan  1 00:00:00 UTC 1970
  # date
  Thu Jan  1 00:00:00 UTC 1970
  # date
  Thu Jan  1 00:00:00 UTC 1970
  #

And yes, that did work before applying this patch :-)

That mean clockevent is running but not clocksource.

And I think that is because I forgot a ~ in the mask for disabling
the T1 timer, so setting up the clockevent disables the clocksource ...

I'll send out a fixed version, plese test!

(BTW I had not clue the 68K maintainer had a platform like
this, fun!)

Yours,
Linus Walleij

Hi Linus,

On 09/01/2012 09:43 AM, Linus Walleij wrote:

On Fri, Aug 31, 2012 at 8:20 AM, Greg Ungerer [off-list ref] wrote:

quoted

Ok, tested on a KS8695 based machine. Boots and runs, obviously
clock is basically working. But 'date' never shows the time
increasing:

   # date
   Thu Jan  1 00:00:00 UTC 1970
   # date
   Thu Jan  1 00:00:00 UTC 1970
   # date
   Thu Jan  1 00:00:00 UTC 1970
   #

And yes, that did work before applying this patch :-)

That mean clockevent is running but not clocksource.

And I think that is because I forgot a ~ in the mask for disabling
the T1 timer, so setting up the clockevent disables the clocksource ...

I'll send out a fixed version, plese test!

Yep, I'll give it a try. I don't have the board in front of me
right now, but when I get in to the office tomorrow I can try it.

(BTW I had not clue the 68K maintainer had a platform like
this, fun!)

Ooohh, I have many weird and wonderful boards, across quite a few
different architectures. I seem to have collected and developed on
quite a few over to many years to remember.

Maintaining m68k/ColdFire is just for fun - it doesn't pay the bills
though :-)

Regards
Greg


------------------------------------------------------------------------
Greg Ungerer  --  Principal Engineer        EMAIL:     gerg at snapgear.com
SnapGear Group, McAfee                      PHONE:       +61 7 3435 2888
8 Gardner Close,                            FAX:         +61 7 3891 3630
Milton, QLD, 4064, Australia                WEB: http://www.SnapGear.com

On Friday 31 August 2012, Linus Walleij wrote:

On Fri, Aug 31, 2012 at 8:20 AM, Greg Ungerer [off-list ref] wrote:

quoted

Ok, tested on a KS8695 based machine. Boots and runs, obviously
clock is basically working. But 'date' never shows the time
increasing:

  # date
  Thu Jan  1 00:00:00 UTC 1970
  # date
  Thu Jan  1 00:00:00 UTC 1970
  # date
  Thu Jan  1 00:00:00 UTC 1970
  #

And yes, that did work before applying this patch :-)

That mean clockevent is running but not clocksource.

And I think that is because I forgot a ~ in the mask for disabling
the T1 timer, so setting up the clockevent disables the clocksource ...

I'll send out a fixed version, plese test!

(BTW I had not clue the 68K maintainer had a platform like
this, fun!)

Note that this platform is one of those we talked about removing
from the kernel for potentially being completely unused. Do we have
reason to believe that people are still using ks8695 for anything
with new kernels?

If any of you are doing that, we'll definitely keep the port around,
the idea is not to break anything that people are actually using.
In that case, I would like to see a MAINTAINERS entry for the platform
so we have a contact for someone who is able to ack and maybe test
patches.

	Arnd

Hi Arnd,

On 03/09/12 04:49, Arnd Bergmann wrote:

On Friday 31 August 2012, Linus Walleij wrote:

quoted

On Fri, Aug 31, 2012 at 8:20 AM, Greg Ungerer [off-list ref] wrote:

quoted

Ok, tested on a KS8695 based machine. Boots and runs, obviously
clock is basically working. But 'date' never shows the time
increasing:

   # date
   Thu Jan  1 00:00:00 UTC 1970
   # date
   Thu Jan  1 00:00:00 UTC 1970
   # date
   Thu Jan  1 00:00:00 UTC 1970
   #

And yes, that did work before applying this patch :-)

That mean clockevent is running but not clocksource.

And I think that is because I forgot a ~ in the mask for disabling
the T1 timer, so setting up the clockevent disables the clocksource ...

I'll send out a fixed version, plese test!

(BTW I had not clue the 68K maintainer had a platform like
this, fun!)

Note that this platform is one of those we talked about removing
from the kernel for potentially being completely unused. Do we have
reason to believe that people are still using ks8695 for anything
with new kernels?

I'll put my hand up as a user of it. I run every release kernel
on KS8695 platforms, though I don't tend to do much testing of
rc kernels on it.

If any of you are doing that, we'll definitely keep the port around,
the idea is not to break anything that people are actually using.
In that case, I would like to see a MAINTAINERS entry for the platform
so we have a contact for someone who is able to ack and maybe test
patches.

I am happy enough to ack and test changes, if no one else wants to
do it. I don't expect to do any real active development on it though.
I do have some board files that would have been nice to push into
mainline, but I have been holding off (for quite a while), hoping
that someone might support DTs on this sub-arch.

Regards
Greg



------------------------------------------------------------------------
Greg Ungerer  --  Principal Engineer        EMAIL:     gerg at snapgear.com
SnapGear Group, McAfee                      PHONE:       +61 7 3435 2888
8 Gardner Close                             FAX:         +61 7 3217 5323
Milton, QLD, 4064, Australia                WEB: http://www.SnapGear.com

On Monday 03 September 2012, Greg Ungerer wrote:

quoted

Note that this platform is one of those we talked about removing
from the kernel for potentially being completely unused. Do we have
reason to believe that people are still using ks8695 for anything
with new kernels?

I'll put my hand up as a user of it. I run every release kernel
on KS8695 platforms, though I don't tend to do much testing of
rc kernels on it.

Ok, very good. Booting every new kernel on a platform is more testing
than a lot of the older platforms get as far as I can tell.

quoted

If any of you are doing that, we'll definitely keep the port around,
the idea is not to break anything that people are actually using.
In that case, I would like to see a MAINTAINERS entry for the platform
so we have a contact for someone who is able to ack and maybe test
patches.

I am happy enough to ack and test changes, if no one else wants to
do it. I don't expect to do any real active development on it though.
I do have some board files that would have been nice to push into
mainline, but I have been holding off (for quite a while), hoping
that someone might support DTs on this sub-arch.

If nobody is actually working on new stuff, we might be better off
with just merging the board files you have. If you don't mind, just
post what you have and then we can decide what to do with them.

	Arnd

On Sun, Sep 2, 2012 at 8:49 PM, Arnd Bergmann [off-list ref] wrote:

On Friday 31 August 2012, Linus Walleij wrote:

quoted

(BTW I had not clue the 68K maintainer had a platform like
this, fun!)

Note that this platform is one of those we talked about removing
from the kernel for potentially being completely unused.

This clock stuff was a lackmus test from my side. The idea
was that if noone tested the patches I would instead
propose a patch deleting the platform.

Guess what: Greg jumps out like jack-in-the-box. I suspect
some of these platforms may have more users than we
believe.

Unsure about the genesis though, it has not even
compiled for a while. I'm poking some of them one by one.

Yours,
Linus Walleij

Hi Arnd,

On 09/03/2012 09:15 PM, Arnd Bergmann wrote:

On Monday 03 September 2012, Greg Ungerer wrote:

quoted

quoted

Note that this platform is one of those we talked about removing
from the kernel for potentially being completely unused. Do we have
reason to believe that people are still using ks8695 for anything
with new kernels?

I'll put my hand up as a user of it. I run every release kernel
on KS8695 platforms, though I don't tend to do much testing of
rc kernels on it.

Ok, very good. Booting every new kernel on a platform is more testing
than a lot of the older platforms get as far as I can tell.

quoted

quoted

If any of you are doing that, we'll definitely keep the port around,
the idea is not to break anything that people are actually using.
In that case, I would like to see a MAINTAINERS entry for the platform
so we have a contact for someone who is able to ack and maybe test
patches.

I am happy enough to ack and test changes, if no one else wants to
do it. I don't expect to do any real active development on it though.
I do have some board files that would have been nice to push into
mainline, but I have been holding off (for quite a while), hoping
that someone might support DTs on this sub-arch.

If nobody is actually working on new stuff, we might be better off
with just merging the board files you have. If you don't mind, just
post what you have and then we can decide what to do with them.

Ok, will do.

Regards
Greg



-- 
------------------------------------------------------------------------
Greg Ungerer  --  Principal Engineer        EMAIL:     gerg at snapgear.com
SnapGear Group, McAfee                      PHONE:       +61 7 3435 2888
8 Gardner Close,                            FAX:         +61 7 3891 3630
Milton, QLD, 4064, Australia                WEB: http://www.SnapGear.com

Hi Liunus,

On 09/03/2012 10:02 PM, Linus Walleij wrote:

On Sun, Sep 2, 2012 at 8:49 PM, Arnd Bergmann [off-list ref] wrote:

quoted

On Friday 31 August 2012, Linus Walleij wrote:

quoted

quoted

(BTW I had not clue the 68K maintainer had a platform like
this, fun!)

Note that this platform is one of those we talked about removing
from the kernel for potentially being completely unused.

This clock stuff was a lackmus test from my side. The idea
was that if noone tested the patches I would instead
propose a patch deleting the platform.

Guess what: Greg jumps out like jack-in-the-box.

That is annoying :-)

I suspect
some of these platforms may have more users than we
believe.

I know the guys at www.opengear.com are still building hardware around
the KS8695. And they update to modern kernels from time to time. So its
not completely obsolete yet. I have some SnapGear boards based around it
too, though they went out of production about 2 years ago.

Regards
Greg


-- 
------------------------------------------------------------------------
Greg Ungerer  --  Principal Engineer        EMAIL:     gerg at snapgear.com
SnapGear Group, McAfee                      PHONE:       +61 7 3435 2888
8 Gardner Close,                            FAX:         +61 7 3891 3630
Milton, QLD, 4064, Australia                WEB: http://www.SnapGear.com

On Monday 03 September 2012, Greg Ungerer wrote:

quoted

I suspect
some of these platforms may have more users than we
believe.

I know the guys at www.opengear.com are still building hardware around
the KS8695. And they update to modern kernels from time to time. So its
not completely obsolete yet. I have some SnapGear boards based around it
too, though they went out of production about 2 years ago.

Ok, good to know. Maybe we can catch their interest with this mail thread
here and get them to contribute upstream as well.

	Arnd

hi,

On Mon, Sep 3, 2012 at 3:24 PM, Arnd Bergmann [off-list ref] wrote:

On Monday 03 September 2012, Greg Ungerer wrote:

quoted

quoted

I suspect
some of these platforms may have more users than we
believe.

I know the guys at www.opengear.com are still building hardware around
the KS8695. And they update to modern kernels from time to time. So its
not completely obsolete yet. I have some SnapGear boards based around it
too, though they went out of production about 2 years ago.

Ok, good to know. Maybe we can catch their interest with this mail thread
here and get them to contribute upstream as well.

Vision System GmbH are (or were) also using the KS8695.


Regards,
  Andrew Victor

On Mon, Sep 03, 2012 at 04:55:41PM +0200, Andrew Victor wrote:

hi,

On Mon, Sep 3, 2012 at 3:24 PM, Arnd Bergmann [off-list ref] wrote:

quoted

On Monday 03 September 2012, Greg Ungerer wrote:

quoted

quoted

I suspect
some of these platforms may have more users than we
believe.

I know the guys at www.opengear.com are still building hardware around
the KS8695. And they update to modern kernels from time to time. So its
not completely obsolete yet. I have some SnapGear boards based around it
too, though they went out of production about 2 years ago.

Ok, good to know. Maybe we can catch their interest with this mail thread
here and get them to contribute upstream as well.

Vision System GmbH are (or were) also using the KS8695.

Ok, cool. Definitely not a candidate for removal based on what we've
seen then.

I would like to consolidate some of the defconfigs though, since
there are currently three of them and the platform supports multi-board
kernels. Anyone objecting to moving over to ks8695_defconfig as a superset
of the current three ones (acs5k{,_tiny}_defconfigs)? I'll post a patch
to NAK tomorrow. :)


-Olof

Hi Arnd,

On 03/09/12 23:24, Arnd Bergmann wrote:

On Monday 03 September 2012, Greg Ungerer wrote:

quoted

quoted

I suspect
some of these platforms may have more users than we
believe.

I know the guys at www.opengear.com are still building hardware around
the KS8695. And they update to modern kernels from time to time. So its
not completely obsolete yet. I have some SnapGear boards based around it
too, though they went out of production about 2 years ago.

Ok, good to know. Maybe we can catch their interest with this mail thread
here and get them to contribute upstream as well.

I have just posted a patch for the SnapGear boards. I had a bit of
info and some code for the OpenGear boards too, so I posted a patch
for some of them too.

Regards
Greg



-- 
------------------------------------------------------------------------
Greg Ungerer  --  Principal Engineer        EMAIL:     gerg at snapgear.com
SnapGear Group, McAfee                      PHONE:       +61 7 3435 2888
8 Gardner Close                             FAX:         +61 7 3217 5323
Milton, QLD, 4064, Australia                WEB: http://www.SnapGear.com