RE: [PATCH-V2 3/3] ARM: OMAP: Make OMAP clocksource source selection runtime

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Index of Archives]     [Linux Arm (vger)]     [ARM Kernel]     [ARM MSM]     [Linux Tegra]     [Linux WPAN Networking]     [Linux Wireless Networking]     [Maemo Users]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite Trails]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux