linux-kernel - Re: [PATCH v2 10/10] clocksource: import ARC timer driver

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Date:   Thu, 3 Nov 2016 15:50:21 -0700
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>
CC:     Noam Camus <noamca@...lanox.com>, <tglx@...utronix.de>,
        <linux-snps-arc@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <Alexey.Brodkin@...opsys.com>
Subject: Re: [PATCH v2 10/10] clocksource: import ARC timer driver

On 11/03/2016 03:38 PM, Daniel Lezcano wrote:
> On Thu, Nov 03, 2016 at 02:31:41PM -0700, Vineet Gupta wrote:
>> This adds support for
>>
>>  - CONFIG_ARC_TIMERS : legacy 32-bit TIMER0 and TIMER1 which count UP
>>    from @CNT to @LIMIT, before optionally triggering an interrupt.
>>    These are programmed using ARC auxiliary register interface.
>>    These are present in all ARC cores (ARC700 and ARC HS38)
>>    TIMER0 serves as clockevent for all ARC linux builds.
>>    TIMER1 is used for clocksource in arc700 builds.
>>
>>  - CONFIG_ARC_TIMERS_64BIT: 64-bit counters, RTC and GFRC found in
>>    ARC HS38 cores. These are independnet IP blocks with different
>>    programming model respectively.
>>
>> Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
>> ---
> 
> [ ... ]
> 
>>  #include <linux/of_irq.h>
>> -#include <asm/irq.h>
>>  
>>  #include <soc/arc/timers.h>
>>  #include <soc/arc/mcip.h>
>> @@ -263,7 +248,7 @@ static irqreturn_t timer_irq_handler(int irq, void *dev_id)
>>  	 * irq_set_chip_and_handler() asked for handle_percpu_devid_irq()
>>  	 */
>>  	struct clock_event_device *evt = this_cpu_ptr(&arc_clockevent_device);
>> -	int irq_reenable = clockevent_state_periodic(evt);
>> +	int irq_reenable __maybe_unused = clockevent_state_periodic(evt);
> 
> Why is needed __maybe_unused ? I see in the previous driver 'irq_reenable' is
> used or is there a change in the previous patches I missed ?

This is needed when not building for CONFIG_ARC (saw this when building for ARM)
write_aux_reg() becomes a no-op which causes a warning:

	write_aux_reg(ARC_REG_TIMER0_CTRL, irq_reenable | TIMER_CTRL_NH);