[PATCHv4 2/2] clocksource: dw_apb_timer_of: Fix read_sched_clock

[Thomas Gleixner]

On Tue, 17 Sep 2013, dinguyen at altera.com wrote: 

> read_sched_clock() should be the same as __apbt_read_clocksource().

So why is it using a separate function in the first place?

> If a separate timer for the sched_clock exist, then read_sched_clock()
> will return an incorrect value. The (sched_io_base + 0x4) needs to be in
> the function for both cases.

It really took me some time to understand the "separate timer" part of
the above explanation. Though that made me look at the actual
implementation and I have to say, that this abuse of the device tree
is really a unique masterpiece:

static int num_called;
static void __init dw_apb_timer_init(struct device_node *timer)
{
        switch (num_called) {
        case 0:
                pr_debug("%s: found clockevent timer\n", __func__);
                add_clockevent(timer);
                of_node_put(timer);
                break;
        case 1:
                pr_debug("%s: found clocksource timer\n", __func__);
                add_clocksource(timer);
                of_node_put(timer);
                init_sched_clock();
                break;
        default:
                break;
        }

        num_called++;
}

So if you can use different nodes for clockevent and clocksource, why
is that supposed to be dependent on the ordering? That's not how DT is
supposed to be used. DT provides a clear description of the hardware,
not some ordering dependent magic amended by utterly useless pr_debug()
constructs.

Thanks,

	tglx