Hello Kyungmin,
On Wed, 21 May 2008, Kyungmin Park wrote:
> On Wed, May 21, 2008 at 3:21 AM, Paul Walmsley <paul@xxxxxxxxx> wrote:
> >
> > static void omap_mask_irq(unsigned int irq)
> > {
> > - int offset = (irq >> 5) << 5;
> > + int offset = irq & (~(IRQ_BITS_PER_REG - 1));
> >
> > - if (irq >= 64)
> > - irq %= 64;
> > - else if (irq >= 32)
> > - irq %= 32;
> > + irq %= IRQ_BITS_PER_REG;
>
> Is it the right conversion?
> If the irq is greater then 32 and less then or equal to 64 it's
> result is different.
> E.g, If irq is 63 then original irq is 63, but new code is 31
Hmm, in that condition, the result looks the same to me: irq % 32, either
way?
More practically, if you look at what it does with that irq variable
afterwards, it seems to be a bug if irq is ever greater than 31:
intc_bank_write_reg(1 << irq, &irq_banks[0], INTC_MIR_CLEAR0 +
offset);
I think the only case where the new code would work differently than the
previous code is if irq > 95. But that would be a bug, since the shift
value would then be > 32, for a 32-bit register.
> And if this code is right, how about to use mask instead of modulo op?
> irq &= (IRQ_BITS_PER_REG - 1);
Hehe, very good point, that would probably save even more cycles! If you
agree with the above, perhaps I can convert the code to use that also,
and add your Signed-off-by also?
- Paul
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