On Sun, Feb 26, 2017 at 03:40:49PM +0100, Andreas F?rber wrote:

Am 25.02.2017 um 22:59 schrieb Daniel Lezcano:

quoted

On Sat, Feb 25, 2017 at 12:25:32AM +0100, Andreas F?rber wrote:

quoted

Am 24.02.2017 um 23:29 schrieb Daniel Lezcano:

quoted

On Fri, Feb 24, 2017 at 04:40:42AM +0100, Andreas F?rber wrote:

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+static struct clock_event_device owl_clockevent = {
+	.name			= "owl_tick",
+	.rating			= 200,
+	.features		= CLOCK_EVT_FEAT_ONESHOT,

Did you consider adding CLOCK_EVT_FEAT_DYNIRQ ?

No, it was not present downstream. Got a good example?

https://lwn.net/Articles/541000/

Looking at your current Nomadik code, it seems I can literally should
just add this flag (done), without needing to implement any new hooks.

On a related topic, how do we determine the cpumask? Downstream and some
in-tree drivers use cpumask_of(0), others use cpu_possible_mask.

If you specify the CLOCK_EVT_FEAT_DYNIRQ, the cpumask is not important as it
will be changed dynamically.

Otherwise, cpumask_of(0) is often the default because it concentrates the
wakeup on a single cpu, allowing the other cpus to go to deep idle state and if
there are two clusters, it allows to have a cluster idle state. That results on
a better energy saving.

The usage of cpu_possible_mask will randomly wakeup any cpu.
 

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Do you spot anything functionally wrong in this driver? Despite adding
this new driver, I am only getting the following additional earlycon output:

[    0.000029] sched_clock: 32 bits at 24MHz, resolution 41ns, wraps
every 89478484971ns
[    0.007888] clocksource: timer: mask: 0xffffffff max_cycles:
0xffffffff, max_idle_ns: 79635851949 ns
[    0.017748] Console: colour dummy device 80x30
[    0.022243] Calibrating delay loop...
[    0.030895] random: fast init done
[    0.231021] random: crng init done

For S900 I'm using the generic timer instead.

I don't get the issue, can you elaborate ?

Found it myself: I forgot to clear the interrupt pending bit in the
interrupt handler routine.

+       writel(OWL_Tx_CTL_PD, owl_timer_base + OWL_T1_CTL);

Now it goes past this point, initializes the real serial driver and
boots up to not finding the rootfs:

[    0.000032] sched_clock: 32 bits at 24MHz, resolution 41ns, wraps
every 89478484971ns
[    0.007898] clocksource: timer: mask: 0xffffffff max_cycles:
0xffffffff, max_idle_ns: 79635851949 ns
[    0.017886] Console: colour dummy device 80x30
[    0.022386] Calibrating delay loop... 405.50 BogoMIPS (lpj=2027520)

May be you should also consider using register_current_timer_delay() instead of
jiffies based delay loops.

[    0.083523] pid_max: default: 32768 minimum: 301

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