On 11/12/2015 08:06 PM, Felipe Balbi wrote:
> Make sure to tell the kernel that AM437x has
> TWD and global timers.
>
> Signed-off-by: Felipe Balbi <balbi@xxxxxx>
> ---
>
> Hi Tony,
>
> now that all dependencies are in place, we can
> finally enable twd and global_timer for AM437x.
>
I'd appreciated if someone can clarify if all described below is valid.
(may be some questions are dummy - sorry).
After all last changes related to TI OMAP clock source/clock event/sched clock's
devices configuration we will have the following for am437x case:
clockevents:
"timer1", clockevent_gpt, .rating = 300, CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT, ti,timer-alwon,
"arm,twd-timer", twd_evt,.rating = 350, CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP
"arm_global_timer", gt_evt, rating = 300, CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERCPU
clocksources:
"jiffies", clocksource_jiffies, rating = 1
if use_gptimer_clksrc
"timer2", clocksource_gpt, .rating = 300, CLOCK_SOURCE_IS_CONTINUOUS,
|-sched_clock_register(dmtimer_read_sched_clock, 32, clksrc.rate);
else
"ti,omap-counter32k", ti_32k_timer, .rating = 250, CLOCK_SOURCE_IS_CONTINUOUS | CLOCK_SOURCE_SUSPEND_NONSTOP,
|-sched_clock_register(omap_32k_read_sched_clock, 32, 32768);
"arm,global-timer", gt_clocksource, .rating = 300, CLOCK_SOURCE_IS_CONTINUOUS
|-sched_clock_register(gt_sched_clock_read, 64, gt_clk_rate);
1) current clockevent device will be registered during registration of clockevent devices
and it will be "arm,twd-timer" - processing sequence follows the way they are listed above.
2) current clocksource will be selected from fs_initcall(clocksource_done_booting);
and it will be "arm,global-timer" or "timer2" if use_gptimer_clksrc
3) sched clock: "arm,global-timer" will be selected as sched_clock *always*,
because it depend on Makefile order (if someone will decide to sort entries
in drivers/clocksource/Makefile then "ti,omap-counter32k" most probably will
be always selected as sched clock).
Uh..
As for me, "timer1" is selected as clockevent device incorrectly, because it's
ti,timer-alwon.
I think, "ti,omap-counter32k" will crash if use_gptimer_clksrc == true, because
corresponding HWmod will not be enabled (not tested this case).
Not sure if "timer2" is selected correctly when both "arm,global-timer" and GP timer
registered as clocksources. ?
Also, It looks like the way sched clock is selected is a little bit unsafe/unclear
(especially taking into account that clocksource dev can be changed through the sysfs
and TI multiSoC kernel).
What is the policy/right way to configure all this clocks?
- should only one clock source be selected for each of them in config file?
- how to dial with sched clock if it depends only on Makefile order ? :(
- should we convert all of them to modules and load depending on current hw?
Could it be reasonable to configure sched clock together with clocksource dev
registration/selection?
- add read_sched field
struct clocksource {
u64 (*read_sched_clock)(void);
- configure sched clock from clocksource core if read_sched != null
Thanks.
> arch/arm/mach-omap2/Kconfig | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/arm/mach-omap2/Kconfig b/arch/arm/mach-omap2/Kconfig
> index 5076d3f334d2..bb3daf0fa7f7 100644
> --- a/arch/arm/mach-omap2/Kconfig
> +++ b/arch/arm/mach-omap2/Kconfig
> @@ -65,6 +65,9 @@ config SOC_AM43XX
> select MACH_OMAP_GENERIC
> select MIGHT_HAVE_CACHE_L2X0
> select HAVE_ARM_SCU
> + select HAVE_ARM_TWD
> + select ARM_GLOBAL_TIMER
> + select CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
>
> config SOC_DRA7XX
> bool "TI DRA7XX"
>
--
regards,
-grygorii
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