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From: Thomas Gleixner <tglx@linutronix.de>
To: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: Russell King <linux@arm.linux.org.uk>,
	Jason Cooper <jason@lakedaemon.net>,
	Linus Walleij <linus.walleij@linaro.org>,
	Andrea Adami <andrea.adami@gmail.com>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	kernel list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/5] ARM: sa1100: use ioremapped memory to access SC registers
Date: Sat, 24 Jan 2015 20:24:26 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.11.1501242021210.5526@nanos> (raw)
In-Reply-To: <CALT56yP+PGCnbUN0BB4QTQ6phxmqL43vRoS_rtoMrgfjAtr3Rw@mail.gmail.com>

On Sat, 24 Jan 2015, Dmitry Eremin-Solenikov wrote:

> 2015-01-24 20:48 GMT+03:00 Thomas Gleixner <tglx@linutronix.de>:
> > On Thu, 15 Jan 2015, Dmitry Eremin-Solenikov wrote:
> >>  static void sa1100_mask_irq(struct irq_data *d)
> >>  {
> >> -     ICMR &= ~BIT(d->hwirq);
> >> +     u32 reg;
> >> +     unsigned long flags;
> >> +
> >> +     raw_spin_lock_irqsave(&lock, flags);
> >
> > What's the exact point of that lock? And how is it related to the
> > $subject of the patch?
> 
> It is needed to protect ICMR register during RMW cycle, isn't it?

The original code has no protection for the RMW either.

And there is a simple reason for this. These functions are guaranteed
to be called with interrupts disabled and this is a uniprocessor
machine and it will never grow SMP support. So interrupts disabled is
serialization enough.

Thanks,

	tglx

  reply	other threads:[~2015-01-24 19:25 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-15 10:09 [PATCH 1/5] ARM: sa1100: add platform functions to handle PWER settings Dmitry Eremin-Solenikov
2015-01-15 10:09 ` [PATCH 2/5] ARM: sa1100: use sa11x0_sc_set_wake() in irq driver Dmitry Eremin-Solenikov
2015-01-15 10:09 ` [PATCH 3/5] ARM: sa1100: use ioremapped memory to access SC registers Dmitry Eremin-Solenikov
2015-01-24 17:48   ` Thomas Gleixner
2015-01-24 17:50     ` Dmitry Eremin-Solenikov
2015-01-24 19:24       ` Thomas Gleixner [this message]
2015-01-24 19:25         ` Dmitry Eremin-Solenikov
2015-01-15 10:09 ` [PATCH 4/5] irqchip: add sa1100 driver Dmitry Eremin-Solenikov
2015-01-15 10:09 ` [PATCH 5/5] ARM: sa1100: drop irq driver Dmitry Eremin-Solenikov
2015-01-21 10:05 ` [PATCH 1/5] ARM: sa1100: add platform functions to handle PWER settings Linus Walleij
2015-01-21 13:37   ` Dmitry Eremin-Solenikov

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