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

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Date:	Tue, 9 Feb 2016 14:38:15 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Noam Camus <noamc@...hip.com>,
	"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

On 02/09/2016 01:36 PM, Noam Camus wrote:
>> From: Daniel Lezcano [mailto:daniel.lezcano@...aro.org] Sent:
>> Monday, February 08, 2016 4:22 PM
>
>>> +	ret = clk_prepare_enable(clk); +	if (ret) +		pr_err("Couldn't
>>> enable parent clock\n"); + +	nps_timer_rate = clk_get_rate(clk);
>
>> If there is an error, you continue the execution of the code. I
>> guess you expect the system to hang in any case with the error in
>> the >console, right ?
>
> Since our clock is root then returned value will always be valid. I
> am far from being expert here, but no one checks for clk_get_rate()
> return value for error. Could you refer to a single place at
> clocksource drivers that checks for error in the return value.

Actually I was referring to clk_prepare_enable, clocksource_register_hz.
Agree clk_get_rate is always valid.

>>> +	ret = clocksource_register_hz(clksrc, nps_timer_rate);
>
>> 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);



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