linux-kernel - Re: [PATCH v2 2/3] rtc: Add Realtek RTD1295

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Date:   Sun, 27 Aug 2017 04:30:08 +0200
From:   Andreas Färber <afaerber@...e.de>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        linux-rtc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        ????????? <jiang.liqin@...iatech.com>,
        linux-kernel@...r.kernel.org, Roc He <hepeng@...oo.tv>
Subject: Re: [PATCH v2 2/3] rtc: Add Realtek RTD1295

Am 27.08.2017 um 04:05 schrieb Andrew Lunn:
> n Sun, Aug 27, 2017 at 02:33:27AM +0200, Andreas Färber wrote:
>> +struct rtd119x_rtc {
>> +	void __iomem *base;
>> +	struct clk *clk;
>> +	struct rtc_device *rtcdev;
>> +	unsigned base_year;
>> +	spinlock_t lock;
> 
> Where is this lock initialised? I would expect a call to
> spin_lock_init() somewhere.

Hm, the spinlock in my irq mux series doesn't have that call either; my
reset driver did have it. The zero initialization appears to work OK,
but you're probably right that it should be there.

> I also wonder what this lock is protecting, which rtc->ops_lock does
> not protect?

By that same argument we could ask why so many drivers (and mine, too)
are calling rtc_valid_tm() when __rtc_read_time() calls it again...

The downstream code is locking inside individual functions such as
check_acr or set_enabled; I adopted it for whole operations only, but
you're right that so far it matches the RTC class ops granularity, so I
can drop it again. The latching discussion had reminded me of locking.

Cheers,
Andreas

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