On Mon, Jan 17, 2011 at 02:00:17PM -0700, Paul Walmsley wrote:
> On Mon, 17 Jan 2011, Russell King wrote:
>
> > On Mon, Jan 17, 2011 at 01:31:47PM -0700, Paul Walmsley wrote:
> > >
> > > OMAP15xx uses the MPU timer for its clocksource, since OMAP15xx doesn't
> > > have GPTIMERs or the 32k sync timer, and the MPU timer code in
> > > mach-omap1/time.c wasn't updated for sched_clock() support.
> > >
> > > Adding an init_fixed_sched_clock() into omap_init_clocksource() should
> > > fix the boot on OMAP15xx/7xx.
> >
> > No, it needs fixing properly. There's no reason the gpt clocksource
> > can't be used for sched_clock.
>
> There's a very good reason why it can't on OMAP15xx/7xx. GPTIMER/DMTIMER
> IP blocks are only present on OMAP1610 and later[1]. Nor is a
> SYNCTIMER_32K IP block present on OMAP15xx/7xx[2].
Yes I realise that. That doesn't negate what I said though. Let me
show you how to do it:
static DEFINE_CLOCK_DATA(cd);
static inline u32 32k_read_cycles(void)
{
...
}
static inline u32 gpt_read_cycles(void)
{
...
}
#if defined(GPTIMER) && defined(32KTIMER)
static u32 (*omap_read_cycles)(void);
#elif defined(32KTIMER)
#define SC_MULT 4000000000u
#define SC_SHIFT 17
#define omap_read_cycles 32k_read_cycles
#else
#define SC_MULT gpt_value_if_fixed
#define SC_SHIFT gpt_value_if_fixed
#define omap_read_cycles gpt_read_cycles
#endif
unsigned long long notrace sched_clock(void)
{
u32 cyc = omap_read_cycles();
#ifdef SC_MULT
return cyc_to_fixed_sched_clock(&cd, cyc, (u32)~0, SC_MULT, SC_SHIFT);
#else
return cyc_to_sched_clock(&cd, cyc, (u32)~0);
#endif
}
static void notrace omap_update_sched_clock(void)
{
u32 cyc = omap_read_cycles();
update_sched_clock(&cd, cyc, (u32)~0);
}
void omap_init_sched_clock(int gpt)
{
unsigned long rate;
#ifndef omap_read_cycles
omap_read_cycles = gpt ? gpt_read_cycles : 32k_read_cycles;
#endif
if (gpt)
rate = gpt_rate;
else
rate = 32768;
#ifdef SC_MULT
init_fixed_sched_clock(&cd, omap_update_sched_clock, 32, rate
SC_MULT, SC_SHIFT);
#else
init_sched_clock(&cd, omap_update_sched_clock, 32, rate);
#endif
}
Both a GPT _and_ 32K sched_clock implementation together, selectable
at runtime or build time depending on what is selected. I'll give you
that it isn't nice code, but it does what's required.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of:
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