Re: [PATCH 3/5] ARM: sa1100: use ioremapped memory to access SC registers

Dmitry Eremin-Solenikov
2015-01-24T19:25:49Z

2015-01-24 22:24 GMT+03:00 Thomas Gleixner <tglx@linutronix.de>:
> 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.

OK, thanks for pointing. I'll update the patchset in a few days.

--
With best wishes
Dmitry