On 11/09/2018 20:42, Chris Brandt wrote:
> On Tuesday, September 11, 2018 1, Rob Herring wrote:
>> Well before we get to initcalls, the kernel calls the arch specific
>> time_init() which (on ARM) calls of_clk_init (for all the reasons
>> above) and then timer_probe(). When timer_probe returns, it is
>> expected that you have setup a clocksource and clockevent. If you
>> haven't, then at some point before we get to initcalls we should hang
>> because we're not getting any timer interrupts and time is not
>> advancing.
>
> What I get now is:
>
> [ 0.000000] timer_probe: no matching timers found
> ...
> ...
> [ 0.000000] clocksource: jiffies: mask: 0xffffffff max_cycles:
> 0xffffffff, max_idle_ns: 19112604462750000 ns
> ...
> ...
>
>
> But then later on in boot, I'll get (with my subsys_initcall timer fix)
>
> ...
> ...
> [ 0.000000] SCSI subsystem initialized
> [ 0.000000] usbcore: registered new interface driver usbfs
> [ 0.000000] usbcore: registered new interface driver hub
> [ 0.000000] usbcore: registered new device driver usb
> [ 0.000000] clocksource: ostm: mask: 0xffffffff max_cycles: 0xffffffff,
> max_idle_ns: 28958491609 ns
> [ 0.000619] sched_clock: 32 bits at 66MHz, resolution 15ns, wraps every
> 32537631224ns
> [ 0.008599] ostm: used for clocksource
> [ 0.018926] ostm: used for clock events
> [ 0.133339] clocksource: Switched to clocksource ostm
> [ 0.821474] NET: Registered protocol family 2
> [ 0.840624] tcp_listen_portaddr_hash hash table entries: 512 (order: 0,
> 4096 bytes)
> [ 0.850549] TCP established hash table entries: 1024 (order: 0, 4096 bytes)
> ...
> ...
>
>
>
>> Maybe you
>> just get lucky and it works as long as no thread blocks (e.g. on a
>> msleep).
>
> You're right. If I put in a msleep() before my timer is up and running, it
> hangs.
>
> As far as I can tell, nothing before device_initcall seems to call anything
> like msleep.
>
>> If things changed and you can setup a timer in an initcall,
>> then why are folks still trying to do things like early platform
>> drivers. Regular drivers would work and we should be able to
>> completely remove CLK_OF_DECLARE and TIMER_OF_DECLARE.
>
> I wonder if the reason is because you can't assign a priority to your
> driver when you declare it with xxx_initcall( ). So, your driver ends up
> in the same table as all the other drivers and you are not guaranteed the
> order in which they probe. So, the answer was to make a NEW table and
> register it using TIMER_OF_DECLARE and CLOCK_OF_DECLARE.
>
> I wonder they just didn't make a clock_initcall() and timer_initcall()
> instead.
What happens if you place the clk_init() before board_time_init() ? in
arch/sh/kernel/time.c
void __init time_init(void)
{
if (board_time_init)
board_time_init();
clk_init();
late_time_init = sh_late_time_init;
}
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