Re: [PATCHv2] ARM: OMAP: gptimer based event monitor driver for oprofile

[Siarhei S. <sia...@no...>]

On Thursday 29 January 2009 22:10:06 ext Kevin Hilman wrote:
> Siarhei Siamashka <sia...@no...> writes:
> > Signed-off-by: Siarhei Siamashka <sia...@no...>
> > ---
> >
> > A second revision of gptimer oprofile patch
> > http://marc.info/?l=linux-omap&m=123143937515088&w=2
> > with the fixes suggested by Tony Lindgren
> >
> > Timers from the CORE domain seem to work best on OMAP3.
> > Also tested the patch on Nokia 770 (OMAP1710).
> >
> > Please let me know if anything else needs to be fixed.
>
> Sorry to review this so late, but...

Don't worry about this. Any kind of feedback is very much welcome. Thanks for
your comments.

> Why do you need to use a hardware timer for this?  If you just need a
> periodic event to fire, you should just use an hrtimer.

A bit more control about how the timer behaves is definitely not critical, but
nice to have nevertheless.

> This would be a good way to make an oprofile model that is generic
> and would not need any HW timer support.

Are there many other platforms which need it? For OMAP3 probably nobody would
even care about any kind generic model if PMU was working reliably.

I will try to check hrtimer and compare it to gptimer based implementation.The
most interesting thing to verify is whether there could be any noticeable
extra overhead related to the use of hrtimer framework.

Another thing to decide is what kind of configurability should be available? 
Should the frequency of periodic event specified in Hz, milliseconds, ticks
of the timer, or whatever else?

> Kevin
>
> >  arch/arm/Kconfig                          |    6 ++
> >  arch/arm/oprofile/Makefile                |    1 +
> >  arch/arm/oprofile/common.c                |    5 ++
> >  arch/arm/oprofile/op_arm_model.h          |    2 +
> >  arch/arm/oprofile/op_model_omap_gptimer.c |   93
> > +++++++++++++++++++++++++++++ 5 files changed, 107 insertions(+), 0
> > deletions(-)
> >  create mode 100644 arch/arm/oprofile/op_model_omap_gptimer.c
> >
> > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > index e7fb201..8774136 100644
> > --- a/arch/arm/Kconfig
> > +++ b/arch/arm/Kconfig
> > @@ -160,6 +160,12 @@ config GENERIC_HARDIRQS_NO__DO_IRQ
> >
> >  if OPROFILE
> >
> > +config OPROFILE_OMAP_GPTIMER
> > +	def_bool y
> > +	depends on ARCH_OMAP
> > +	select CONFIG_OMAP_32K_TIMER
> > +	select CONFIG_OMAP_DM_TIMER
> > +
> >  config OPROFILE_ARMV6
> >  	def_bool y
> >  	depends on CPU_V6 && !SMP
> > diff --git a/arch/arm/oprofile/Makefile b/arch/arm/oprofile/Makefile
> > index 88e31f5..fc2bc02 100644
> > --- a/arch/arm/oprofile/Makefile
> > +++ b/arch/arm/oprofile/Makefile
> > @@ -8,6 +8,7 @@ DRIVER_OBJS = $(addprefix ../../../drivers/oprofile/, \
> >
> >  oprofile-y				:= $(DRIVER_OBJS) common.o backtrace.o
> >  oprofile-$(CONFIG_CPU_XSCALE)		+= op_model_xscale.o
> > +oprofile-$(CONFIG_OPROFILE_OMAP_GPTIMER)	+= op_model_omap_gptimer.o
> >  oprofile-$(CONFIG_OPROFILE_ARM11_CORE)	+= op_model_arm11_core.o
> >  oprofile-$(CONFIG_OPROFILE_ARMV6)	+= op_model_v6.o
> >  oprofile-$(CONFIG_OPROFILE_MPCORE)	+= op_model_mpcore.o
> > diff --git a/arch/arm/oprofile/common.c b/arch/arm/oprofile/common.c
> > index 3fcd752..add3cb4 100644
> > --- a/arch/arm/oprofile/common.c
> > +++ b/arch/arm/oprofile/common.c
> > @@ -133,6 +133,11 @@ int __init oprofile_arch_init(struct
> > oprofile_operations *ops)
> >
> >  	ops->backtrace = arm_backtrace;
> >
> > +/* comes first, so that it can be overrided by a better implementation
> > */ +#ifdef CONFIG_OPROFILE_OMAP_GPTIMER
> > +	spec = &op_omap_gptimer_spec;
> > +#endif
> > +
> >  #ifdef CONFIG_CPU_XSCALE
> >  	spec = &op_xscale_spec;
> >  #endif
> > diff --git a/arch/arm/oprofile/op_arm_model.h
> > b/arch/arm/oprofile/op_arm_model.h index 8c4e4f6..db936da 100644
> > --- a/arch/arm/oprofile/op_arm_model.h
> > +++ b/arch/arm/oprofile/op_arm_model.h
> > @@ -24,6 +24,8 @@ struct op_arm_model_spec {
> >  extern struct op_arm_model_spec op_xscale_spec;
> >  #endif
> >
> > +extern struct op_arm_model_spec op_omap_gptimer_spec;
> > +
> >  extern struct op_arm_model_spec op_armv6_spec;
> >  extern struct op_arm_model_spec op_mpcore_spec;
> >  extern struct op_arm_model_spec op_armv7_spec;
> > diff --git a/arch/arm/oprofile/op_model_omap_gptimer.c
> > b/arch/arm/oprofile/op_model_omap_gptimer.c new file mode 100644
> > index 0000000..98f7d2b
> > --- /dev/null
> > +++ b/arch/arm/oprofile/op_model_omap_gptimer.c
> > @@ -0,0 +1,93 @@
> > +/**
> > + * OMAP gptimer based event monitor driver for oprofile
> > + *
> > + * Copyright (C) 2009 Nokia Corporation
> > + * Author: Siarhei Siamashka <sia...@no...>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2 as
> > + * published by the Free Software Foundation.
> > + *
> > + */
> > +
> > +#include <linux/types.h>
> > +#include <linux/oprofile.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/irq.h>
> > +
> > +#include <mach/dmtimer.h>
> > +
> > +#include "op_counter.h"
> > +#include "op_arm_model.h"
> > +
> > +static struct omap_dm_timer *gptimer;
> > +
> > +static int gptimer_init(void)
> > +{
> > +	return 0;
> > +}
> > +
> > +static int gptimer_setup(void)
> > +{
> > +	return 0;
> > +}
> > +
> > +static irqreturn_t gptimer_interrupt(int irq, void *arg)
> > +{
> > +	omap_dm_timer_write_status(gptimer, OMAP_TIMER_INT_OVERFLOW);
> > +	oprofile_add_sample(get_irq_regs(), 0);
> > +	return IRQ_HANDLED;
> > +}
> > +
> > +static int gptimer_start(void)
> > +{
> > +	int err;
> > +	u32 count = counter_config[0].count;
> > +
> > +	BUG_ON(gptimer != NULL);
> > +	/* First try to request timers from CORE power domain for OMAP3 */
> > +	if (cpu_is_omap34xx()) {
> > +		gptimer = omap_dm_timer_request_specific(10);
> > +		if (gptimer == NULL)
> > +			gptimer = omap_dm_timer_request_specific(11);
> > +	}
> > +	/* Just any timer would be fine */
> > +	if (gptimer == NULL)
> > +		gptimer = omap_dm_timer_request();
> > +	if (gptimer == NULL)
> > +		return -ENODEV;
> > +
> > +	omap_dm_timer_set_source(gptimer, OMAP_TIMER_SRC_32_KHZ);
> > +	err = request_irq(omap_dm_timer_get_irq(gptimer), gptimer_interrupt,
> > +				IRQF_DISABLED, "oprofile gptimer", NULL);
> > +	if (err) {
> > +		omap_dm_timer_free(gptimer);
> > +		gptimer = NULL;
> > +		printk(KERN_ERR "oprofile: unable to request gptimer IRQ\n");
> > +		return err;
> > +	}
> > +
> > +	if (count < 1)
> > +		count = 1;
> > +
> > +	omap_dm_timer_set_load_start(gptimer, 1, 0xffffffff - count);
> > +	omap_dm_timer_set_int_enable(gptimer, OMAP_TIMER_INT_OVERFLOW);
> > +	return 0;
> > +}
> > +
> > +static void gptimer_stop(void)
> > +{
> > +	omap_dm_timer_set_int_enable(gptimer, 0);
> > +	free_irq(omap_dm_timer_get_irq(gptimer), NULL);
> > +	omap_dm_timer_free(gptimer);
> > +	gptimer = NULL;
> > +}
> > +
> > +struct op_arm_model_spec op_omap_gptimer_spec = {
> > +	.init		= gptimer_init,
> > +	.num_counters	= 1,
> > +	.setup_ctrs	= gptimer_setup,
> > +	.start		= gptimer_start,
> > +	.stop		= gptimer_stop,
> > +	.name		= "hrtimer",
> > +};
> > --
> > 1.5.6.5