[RFC/RFT 1/3] iop: clocksource support

[linus.ml.walleij@gmail.com (Linus Walleij)]

Tjenare Mikael,

2009/8/22 Mikael Pettersson <mikpe@it.uu.se>:

> This updates the IOP platform to expose the free-running
> timer 1 as a clocksource object. This timer is now also
> properly initialised, which requires a new write_tcr1()
> function from the mach implementation code. Apart from the
> explicit initialisation, there is no functional change in
> how timer 1 is programmed.
>
> The one concern I have is whether the clocksource .shift
> value of 20 is appropriate for timer frequencies in the
> 200/266/333 MHz range which seem to be typical for IOP.
>
> Tested on n2100, compile-tested for all plat-iop machines.
>
> Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
> ---
> ?arch/arm/include/asm/hardware/iop3xx.h ? ?| ? ?5 +++++
> ?arch/arm/mach-iop13xx/include/mach/time.h | ? ?5 +++++
> ?arch/arm/plat-iop/time.c ? ? ? ? ? ? ? ? ?| ? 27 +++++++++++++++++++++++++++
> ?3 files changed, 37 insertions(+)
>
> diff -rupN linux-2.6.31-rc7/arch/arm/include/asm/hardware/iop3xx.h linux-2.6.31-rc7.arm-iop-1-clocksource/arch/arm/include/asm/hardware/iop3xx.h
> --- linux-2.6.31-rc7/arch/arm/include/asm/hardware/iop3xx.h ? ? 2008-10-11 10:43:49.000000000 +0200
> +++ linux-2.6.31-rc7.arm-iop-1-clocksource/arch/arm/include/asm/hardware/iop3xx.h ? ? ? 2009-08-22 12:06:28.000000000 +0200
> @@ -259,6 +259,11 @@ static inline u32 read_tcr1(void)
> ? ? ? ?return val;
> ?}
>
> +static inline void write_tcr1(u32 val)
> +{
> + ? ? ? asm volatile("mcr p6, 0, %0, c3, c1, 0" : : "r" (val));
> +}
> +
> ?static inline void write_trr0(u32 val)
> ?{
> ? ? ? ?asm volatile("mcr p6, 0, %0, c4, c1, 0" : : "r" (val));
> diff -rupN linux-2.6.31-rc7/arch/arm/mach-iop13xx/include/mach/time.h linux-2.6.31-rc7.arm-iop-1-clocksource/arch/arm/mach-iop13xx/include/mach/time.h
> --- linux-2.6.31-rc7/arch/arm/mach-iop13xx/include/mach/time.h ?2008-12-25 15:54:13.000000000 +0100
> +++ linux-2.6.31-rc7.arm-iop-1-clocksource/arch/arm/mach-iop13xx/include/mach/time.h ? ?2009-08-22 12:06:28.000000000 +0200
> @@ -90,6 +90,11 @@ static inline u32 read_tcr1(void)
> ? ? ? ?return val;
> ?}
>
> +static inline void write_tcr1(u32 val)
> +{
> + ? ? ? asm volatile("mcr p6, 0, %0, c3, c9, 0" : : "r" (val));
> +}
> +
> ?static inline void write_trr0(u32 val)
> ?{
> ? ? ? ?asm volatile("mcr p6, 0, %0, c4, c9, 0" : : "r" (val));
> diff -rupN linux-2.6.31-rc7/arch/arm/plat-iop/time.c linux-2.6.31-rc7.arm-iop-1-clocksource/arch/arm/plat-iop/time.c
> --- linux-2.6.31-rc7/arch/arm/plat-iop/time.c ? 2008-12-25 15:54:14.000000000 +0100
> +++ linux-2.6.31-rc7.arm-iop-1-clocksource/arch/arm/plat-iop/time.c ? ? 2009-08-22 12:06:28.000000000 +0200
> @@ -19,6 +19,7 @@
> ?#include <linux/init.h>
> ?#include <linux/timex.h>
> ?#include <linux/io.h>
> +#include <linux/clocksource.h>
> ?#include <mach/hardware.h>
> ?#include <asm/irq.h>
> ?#include <asm/uaccess.h>
> @@ -26,6 +27,23 @@
> ?#include <asm/mach/time.h>
> ?#include <mach/time.h>
>
> +/*
> + * IOP clocksource (free-running timer 1).
> + */
> +static cycle_t iop_clocksource_read(struct clocksource *unused)
> +{
> + ? ? ? return 0xffffffffu - read_tcr1();

So tcr1 counts downwards and wraps around?

> +}
> +
> +static struct clocksource iop_clocksource = {
> + ? ? ? .name ? ? ? ? ? = "iop_timer1",
> + ? ? ? .rating ? ? ? ? = 300,
> + ? ? ? .read ? ? ? ? ? = iop_clocksource_read,
> + ? ? ? .mask ? ? ? ? ? = CLOCKSOURCE_MASK(32),
> + ? ? ? .shift ? ? ? ? ?= 20, ? /* ??? crude guesstimate */

Calculate this using the algorithm in arch/mips/kernel/time.c
they have a dynamically changing clocksource...

> + ? ? ? .flags ? ? ? ? ?= CLOCK_SOURCE_IS_CONTINUOUS,
> +};
> +
> ?static unsigned long ticks_per_jiffy;
> ?static unsigned long ticks_per_usec;
> ?static unsigned long next_jiffy_time;
> @@ -99,8 +117,17 @@ void __init iop_init_time(unsigned long
> ? ? ? ? */
> ? ? ? ?write_trr0(ticks_per_jiffy - 1);
> ? ? ? ?write_tmr0(timer_ctl);
> +
> + ? ? ? /*
> + ? ? ? ?* Set up free-running clocksource timer 1.
> + ? ? ? ?*/
> ? ? ? ?write_trr1(0xffffffff);
> + ? ? ? write_tcr1(0xffffffff);
> ? ? ? ?write_tmr1(timer_ctl);
> + ? ? ? iop_clocksource.mult =
> + ? ? ? ? ? ? ? clocksource_hz2mult(tick_rate,
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? iop_clocksource.shift);
> + ? ? ? clocksource_register(&iop_clocksource);
>
> ? ? ? ?setup_irq(IRQ_IOP_TIMER0, &iop_timer_irq);
> ?}
>

Linus Walleij