From: bill4carson@gmail.com (bill4carson)
To: kernelnewbies@lists.kernelnewbies.org
Subject: fiq vs normal interrupt request mode
Date: Thu, 29 Mar 2012 17:18:10 +0800 [thread overview]
Message-ID: <4F7428D2.6030501@gmail.com> (raw)
In-Reply-To: <CAGA5_H5X+r-SJvA7yckgtPwOFr25ye-EkMq98w55FQQhA8XHDA@mail.gmail.com>
On 2012?03?29? 15:06, Rajasekhar Pulluru wrote:
> Hi,
>
> While registering for an interrupt handler, we could specify
> IRQF_DISABLED flag to request_irq() to disable all other interrupts
> while the handler's execution, except the one that's being registered.
> I understand that this flag's usage is reserved only for
> performance-sensitive interrupts that needs to execute quickly and
> setting this for general (non-performance sensitive cases) use is
> considered bad.
>
> Qn.1: Is this the fast way of interrupt handling? Does this flag
> distinguish between fast and slow interrupts?
>
> Arm supports several processor modes that includes FIQ and Interrupt
> request mode. FIQ has higher priority over normal interrupt mode.
>
> Qn.2: Is FIQ mode supported by ARM is equivalent to doing
> IRQF_DISABLED in hardware? What is/are the significance/advantages of
> FIQ mode?
>
From software side:
ARM FIQ implementation COPY FIQ handler right at FIQ vector, however
IRQ implementation needs to interrogate interrupt controller to find
which interrupt fired.
From hardware side:
FIQ save less registers than IRQ, also has higher priority than IRQ.
> Thanks& Regards,
> Rajasekhar
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>
--
Love each day!
--bill
prev parent reply other threads:[~2012-03-29 9:18 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-29 7:06 fiq vs normal interrupt request mode Rajasekhar Pulluru
2012-03-29 9:18 ` bill4carson [this message]
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