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From: Segher Boessenkool <segher@kernel.crashing.org>
Subject: Re: [RFC PATCH 11/19] powerpc: gamecube/wii: flipper interrupt
	controller support
Date: Thu, 26 Nov 2009 22:52:04 +0100
To: Albert Herranz <albert_herranz@yahoo.es>
Cc: linuxppc-dev@lists.ozlabs.org
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>> Maybe using FLIPPER (or GAMECUBE_FLIPPER) instead of GAMECUBE_COMMON
>> is a good name?
>
> I'd prefer to not use a name that implies a specific hardware to  
> describe two (mostly) similar but different hardwares.

Hollywood is 100% compatible to Flipper though.

>>> +/*
>>> + * Each interrupt has a corresponding bit in both
>>> + * the Interrupt Cause (ICR) and Interrupt Mask (IMR) registers.
>>> + *
>>> + * Enabling/disabling an interrupt line involves asserting/clearing
>>> + * the corresponding bit in IMR. ACK'ing a request simply involves
>>> + * asserting the corresponding bit in ICR.
>>> + */

I looked it up in YAGCD; it says that _reading_ the ICR reg already
acks all interrupts (and clears the bits), you never write this reg!

>>> +static void flipper_pic_ack(unsigned int virq)
>>> +{
>>> +    int irq = virq_to_hw(virq);
>>> +    void __iomem *io_base = get_irq_chip_data(virq);
>>> +
>>> +    set_bit(irq, io_base + FLIPPER_ICR);
>>> +}
>>
>> So it should be a simple write instead of an RMW here, right?
>> As it is you are ACKing _all_ IRQs as far as I can see.
>>
>
> No, it acks just a single IRQ.

No it doesn't.  Say IRQs 1 and 3 are asserted, so the reg contains 0x0a.
Now you want to ack IRQ1; set_bit() will write 0x0a | 0x02, not just  
0x02.


Segher