On Fri, Mar 30, 2012 at 21:04:40, Hunter, Jon wrote:
> Hi Vaibhav,
>
> On 3/30/2012 8:54, Vaibhav Hiremath wrote:
>
> > Current OMAP code supports couple of clocksource options based
> > on compilation flag (CONFIG_OMAP_32K_TIMER). The 32KHz sync-timer
> > and a gptimer which can run on 32KHz or system clock (e.g 38.4 MHz).
> > So there can be 3 options -
> >
> > 1. 32KHz sync-timer
> > 2. Sys_clock based (e.g 13/19.2/26/38.4 MHz) gptimer
> > 3. 32KHz based gptimer.
> >
> > The optional gptimer based clocksource was added so that it can
> > give the high precision than sync-timer, so expected usage was 2
> > and not 3.
> > Unfortunately option 2, clocksource doesn't meet the requirement of
> > free-running clock as per clocksource need. It stops in low power states
> > when sys_clock is cut. That makes gptimer based clocksource option
> > useless for OMAP2/3/4 devices with sys_clock as a clock input.
> > Option 3 will still work but it is no better than 32K sync-timer
> > based clocksource.
> >
> > So ideally we can kill the gptimer based clocksource option but there
> > are some OMAP based derivative SoCs like AM33XX which doesn't have
> > 32K sync-timer hardware IP and need to fallback on 32KHz based gptimer
> > clocksource.
> > Considering above, make sync-timer and gptimer clocksource runtime
> > selectable so that both OMAP and AMXXXX continue to use the same code.
> >
> > Use hwmod database lookup mechanism, through which at run-time
> > we can identify availability of 32k-sync timer on the device,
> > else fall back to gptimer.
> >
> > Signed-off-by: Vaibhav Hiremath <hvaibhav@xxxxxx>
> > Signed-off-by: Felipe Balbi <balbi@xxxxxx>
> > CC: Santosh Shilimkar <santosh.shilimkar@xxxxxx>
> > Cc: Benoit Cousson <b-cousson@xxxxxx>
> > Cc: Tony Lindgren <tony@xxxxxxxxxxx>
> > Cc: Paul Walmsley <paul@xxxxxxxxx>
> > Cc: Tarun Kanti DebBarma <tarun.kanti@xxxxxx>
> > Cc: Ming Lei <tom.leiming@xxxxxxxxx>
> > ---
> > arch/arm/mach-omap1/timer32k.c | 6 ++-
> > arch/arm/mach-omap2/timer.c | 45 +++++++++-------
> > arch/arm/plat-omap/counter_32k.c | 86 ++++++++++++-----------------
> > arch/arm/plat-omap/include/plat/common.h | 2 +-
> > 4 files changed, 68 insertions(+), 71 deletions(-)
>
> [...]
>
> > @@ -280,13 +265,33 @@ static void __init omap2_gp_clocksource_init(int gptimer_id,
> > const char *fck_source)
> > {
> > int res;
> > + struct omap_hwmod *oh;
> > + const char *oh_name = "counter_32k";
> > +
> > + /*
> > + * First check for availability for 32k-sync timer.
> > + *
> > + * In case of failure in finding 32k_counter module or
> > + * registering it as clocksource, execution will fallback to
> > + * gp-timer.
> > + */
> > + oh = omap_hwmod_lookup(oh_name);
> > + if (oh && oh->slaves_cnt != 0) {
> > + u32 pbase;
> > + unsigned long size;
> > +
> > + pbase = oh->slaves[0]->addr->pa_start + 0x10;
> > + size = oh->slaves[0]->addr->pa_end -
> > + oh->slaves[0]->addr->pa_start;
> > + res = omap_init_clocksource_32k(pbase, size);
> > + if (!res)
> > + return;
>
>
> If omap_init_clocksource_32k() fails should we also call BUG_ON here?
>
I don't think we should do that, for following reasons,
- There will be platforms without 32k_counter modules, like am33xx.
For them, this BUG_ON will miss-leading.
- pr_err is already used to provide failure in this function.
- We have safe fallback option here.
> > + }
> >
> > + /* Fall back to gp-timer code */
> > res = omap_dm_timer_init_one(&clksrc, gptimer_id, fck_source);
> > BUG_ON(res);
> >
> > - pr_info("OMAP clocksource: GPTIMER%d at %lu Hz\n",
> > - gptimer_id, clksrc.rate);
> > -
> > __omap_dm_timer_load_start(&clksrc,
> > OMAP_TIMER_CTRL_ST | OMAP_TIMER_CTRL_AR, 0, 1);
> > setup_sched_clock(dmtimer_read_sched_clock, 32, clksrc.rate);
> > @@ -294,8 +299,10 @@ static void __init omap2_gp_clocksource_init(int gptimer_id,
> > if (clocksource_register_hz(&clocksource_gpt, clksrc.rate))
> > pr_err("Could not register clocksource %s\n",
> > clocksource_gpt.name);
> > + else
> > + pr_info("OMAP clocksource: GPTIMER%d at %lu Hz\n",
> > + gptimer_id, clksrc.rate);
> > }
> > -#endif
> >
> > #define OMAP_SYS_TIMER_INIT(name, clkev_nr, clkev_src, \
> > clksrc_nr, clksrc_src) \
> > diff --git a/arch/arm/plat-omap/counter_32k.c b/arch/arm/plat-omap/counter_32k.c
> > index 5068fe5..c1af18c 100644
> > --- a/arch/arm/plat-omap/counter_32k.c
> > +++ b/arch/arm/plat-omap/counter_32k.c
> > @@ -35,8 +35,6 @@
> > */
> > static void __iomem *timer_32k_base;
> >
> > -#define OMAP16XX_TIMER_32K_SYNCHRONIZED 0xfffbc410
> > -
> > static u32 notrace omap_32k_read_sched_clock(void)
> > {
> > return timer_32k_base ? __raw_readl(timer_32k_base) : 0;
> > @@ -68,54 +66,42 @@ void read_persistent_clock(struct timespec *ts)
> > *ts = *tsp;
> > }
> >
> > -int __init omap_init_clocksource_32k(void)
> > +int __init omap_init_clocksource_32k(u32 pbase, unsigned long size)
> > {
> > - static char err[] __initdata = KERN_ERR
> > - "%s: can't register clocksource!\n";
> > -
> > - if (cpu_is_omap16xx() || cpu_class_is_omap2()) {
> > - u32 pbase;
> > - unsigned long size = SZ_4K;
> > - void __iomem *base;
> > - struct clk *sync_32k_ick;
> > -
> > - if (cpu_is_omap16xx()) {
> > - pbase = OMAP16XX_TIMER_32K_SYNCHRONIZED;
> > - size = SZ_1K;
> > - } else if (cpu_is_omap2420())
> > - pbase = OMAP2420_32KSYNCT_BASE + 0x10;
> > - else if (cpu_is_omap2430())
> > - pbase = OMAP2430_32KSYNCT_BASE + 0x10;
> > - else if (cpu_is_omap34xx())
> > - pbase = OMAP3430_32KSYNCT_BASE + 0x10;
> > - else if (cpu_is_omap44xx())
> > - pbase = OMAP4430_32KSYNCT_BASE + 0x10;
> > - else
> > - return -ENODEV;
> > -
> > - /* For this to work we must have a static mapping in io.c for this area */
> > - base = ioremap(pbase, size);
> > - if (!base)
> > - return -ENODEV;
> > -
> > - sync_32k_ick = clk_get(NULL, "omap_32ksync_ick");
> > - if (!IS_ERR(sync_32k_ick))
> > - clk_enable(sync_32k_ick);
>
> > -
>
> > - timer_32k_base = base;
> > -
> > - /*
> > - * 120000 rough estimate from the calculations in
> > - * __clocksource_updatefreq_scale.
> > - */
> > - clocks_calc_mult_shift(&persistent_mult, &persistent_shift,
> > - 32768, NSEC_PER_SEC, 120000);
> > -
> > - if (clocksource_mmio_init(base, "32k_counter", 32768, 250, 32,
> > - clocksource_mmio_readl_up))
> > - printk(err, "32k_counter");
> > -
> > - setup_sched_clock(omap_32k_read_sched_clock, 32, 32768);
> > - }
> > + void __iomem *base;
> > + struct clk *sync_32k_ick;
> > +
> > + if (!pbase || !size)
> > + return -ENODEV;
> > + /*
> > + * For this to work we must have a static mapping in io.c
> > + * for this area
> > + */
> > + base = ioremap(pbase, size);
> > + if (!base)
> > + return -ENODEV;
> > +
> > + sync_32k_ick = clk_get(NULL, "omap_32ksync_ick");
> > + if (!IS_ERR(sync_32k_ick))
> > + clk_enable(sync_32k_ick);
>
>
> I know that this is carry over from the original code, but seems that if
> clk_get fails we should return an error. So maybe ...
>
I thought of this before, but again the next thought came to my mind was,
somebody might have done this for some specific reasons, may be OMAP1
dependency or something? So I choose it to keep it as is...
So before doing this, I thing we should conform from the original author
about this implementation.
May be Paul can comment and conform on this.
Thanks,
Vaibhav
>
> sync_32k_ick = clk_get(NULL, "omap_32ksync_ick");
> if (IS_ERR(sync_32k_ick))
> return -ENODEV;
>
> clk_enable(sync_32k_ick);
>
> > +
> > + timer_32k_base = base;
> > +
> > + /*
> > + * 120000 rough estimate from the calculations in
> > + * __clocksource_updatefreq_scale.
> > + */
> > + clocks_calc_mult_shift(&persistent_mult, &persistent_shift,
> > + 32768, NSEC_PER_SEC, 120000);
> > +
> > + if (clocksource_mmio_init(base, "32k_counter", 32768, 250, 32,
> > + clocksource_mmio_readl_up))
> > + pr_err("32k_counter: can't register clocksource!\n");
> > +
>
>
> Extra line added here that should be removed.
>
Ohhh ok. Will remove this in next version.
I will wait for Tony's comment on this patch series, I need to
align with Tony on selection of clocksource between 32k Vs gptimer.
Thanks,
Vaibhav
> Cheers
> Jon
>
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