linux-kernel - Re: [PATCH 03/24] MIPS: Provide a generic plat_irq

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Date:	Wed, 17 Sep 2014 09:36:06 -0700
From:	Andrew Bresticker <abrestic@...omium.org>
To:	Qais Yousef <qais.yousef@...tec.com>
Cc:	Ralf Baechle <ralf@...ux-mips.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Jeffrey Deans <jeffrey.deans@...tec.com>,
	Markos Chandras <markos.chandras@...tec.com>,
	Paul Burton <paul.burton@...tec.com>,
	Jonas Gorski <jogo@...nwrt.org>,
	John Crispin <blogic@...nwrt.org>,
	David Daney <ddaney.cavm@...il.com>,
	Linux-MIPS <linux-mips@...ux-mips.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/24] MIPS: Provide a generic plat_irq_dispatch

On Wed, Sep 17, 2014 at 1:56 AM, Qais Yousef <qais.yousef@...tec.com> wrote:
> Hi Andrew,
>
>
> On 09/16/2014 12:51 AM, Andrew Bresticker wrote:
>>
>> For platforms which boot with device-tree or have correctly chained
>> all external interrupt controllers, a generic plat_irq_dispatch() can
>> be used.  Implement a plat_irq_dispatch() which simply handles all the
>> pending interrupts as reported by C0_Cause.
>>
>> Signed-off-by: Andrew Bresticker <abrestic@...omium.org>
>> ---
>>   arch/mips/kernel/irq_cpu.c | 15 +++++++++++++++
>>   1 file changed, 15 insertions(+)
>>
>> diff --git a/arch/mips/kernel/irq_cpu.c b/arch/mips/kernel/irq_cpu.c
>> index ca98a9f..f17bd08 100644
>> --- a/arch/mips/kernel/irq_cpu.c
>> +++ b/arch/mips/kernel/irq_cpu.c
>> @@ -94,6 +94,21 @@ static struct irq_chip mips_mt_cpu_irq_controller = {
>>         .irq_eoi        = unmask_mips_irq,
>>   };
>>   +asmlinkage void __weak plat_irq_dispatch(void)
>> +{
>> +       unsigned long pending = read_c0_cause() & read_c0_status() &
>> ST0_IM;
>> +       int irq;
>> +
>> +       if (!pending) {
>> +               spurious_interrupt();
>> +               return;
>> +       }
>> +
>> +       pending >>= CAUSEB_IP;
>> +       for_each_set_bit(irq, &pending, 8)
>> +               do_IRQ(MIPS_CPU_IRQ_BASE + irq);
>> +}
>> +
>
>
> If I read the for_each_set_bit() macro correctly it'll iterate through the
> bits from least to most significant ones which is the reversed priority
> expected. Some platforms set timer interrupt to bit 7 which is should be the
> highest priority interrupt. Also when cpu_has_vint is set the hardware
> prioritirise from most significant to least significant bits so if
> plat_irq_dispatch() is used with set_vi_handler() it'll cause interrupts to
> be serviced in the wrong order.

Ah, right.  I'll flip the order here.
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