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

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Date:	Tue, 9 Feb 2016 21:47:03 +0000
From:	Noam Camus <noamc@...hip.com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	"linux-snps-arc@...ts.infradead.org" 
	<linux-snps-arc@...ts.infradead.org>,
	"marc.zyngier@....com" <marc.zyngier@....com>,
	Chris Metcalf <cmetcalf@...hip.com>,
	Tal Zilcer <talz@...hip.com>,
	Gilad Ben Yossef <giladb@...hip.com>,
	Rob Herring <robh+dt@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <john.stultz@...aro.org>
Subject: Re: [PATCH v3 2/3] clocksource: Add NPS400 timers driver

>From: Daniel Lezcano <daniel.lezcano@...aro.org>
>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()?
What if there is another clocksource in DT (even with worse rating)?
I still prefer using it then having non workable machine.

>>
>>> 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?

Thanks for your patience
-Noam