Re: [PATCH v3 2/3] clocksource: Add NPS400 timers driver

[Daniel Lezcano]

On 02/09/2016 10:47 PM, Noam Camus wrote:
> > From: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> Sent: Tuesday,
> > February 9, 2016 3:38 PM
>
> > Actually I was referring to clk_prepare_enable,
> > clocksource_register_hz. Agree clk_get_rate is always valid.
> Thanks for making this clear. Any way as you can see I do call
> pr_err() in case of error just like most drivers around. By "hang" do
> you mean calling panic()?

No. I meant the errors are caught but no action is taken, the execution
continues normally as nothing wrong happened. This is why I asked if you
expect the host to hang at boot time with the last error as a hint.

I was expecting to see a call to clk_disable_unprepare if
clocksource_register_hz fails, and returning 'ret' if clk_prepare_enable
fails.

> What if there is another clocksource in DT (even with worse rating)?
> I still prefer using it then having non workable machine.

You are right. This is why failing gracefully in the init function is
important.

> > > > You can simplify the driver even more by using
> > > > clocksource_mmio_init.
> > > Since my base address depends on cluster number, which CPU is
> > > part of,  this interface is not much of a use. On top of that it
> > > assumes that I am little endian by using readl family
> > > accessories.
>
> > Why can't you use ?
>
> > clocksource_mmio_init(nps_msu_reg_low_addr, "EZnps-tick",
> > nps_timer_rate, 32, nps_clksrc_read);
>
> I believe that the simplification is meant for drivers that can
> actually use the clocksource_mmio..() accessories. Could you explain
> what is the advantage here, for my case, to use clocksource_mmio
> driver?

Using the mmio generic code will save:

+static struct clocksource nps_counter = {
+	.name	= "EZnps-tick",
+	.rating = 301,
+	.read   = nps_clksrc_read,
+	.mask   = CLOCKSOURCE_MASK(32),
+	.flags  = CLOCK_SOURCE_IS_CONTINUOUS,
+};

Up to you.

  -- Daniel

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