[PATCH 1/2] arm: samsung: move timer irq numbers to end of linux irq space

[Thomas Abraham]

Hi Russell,

On 7 October 2011 03:45, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
> On Fri, Oct 07, 2011 at 02:41:42AM +0530, Thomas Abraham wrote:
>> All of Samsung's s5p platforms have timer irqs statically mapped from linux
>> irq numbers 11 to 15. These timer irqs are moved to end of the statically
>> mapped linux irq space and the hardware irqs, which were statically mapped
>> starting from 32 is moved to start from 0. The NR_IRQS macro is consolidated
>> for all the s5p platforms in this process.
>
> Am I reading this patch correctly - in that on platforms with the GIC,
> you add 32 to the GIC IRQ number _just_ to avoid the possibility that
> IRQs 11-15 are seen as valid?
>
> Or to put it another way, you're trying to ensure that if these timer
> IRQs are requested, they will fail?
>

This patch is applicable for s5p64x0, s5pc100, s5pv210 and exynos4.
Exynos4 has GIC and the rest use VIC.

For all these platforms, the five hardware timer irqs are connected to
GIC/VIC at some hardware irq number (in exynos it is GIC_ID 69 to 73
for five timers). When any of these hardware interrupt occurs, its
interrupt handler calls generic_handle_irq() with linux irq number
11/12/13/14/15 for timer 0/1/2/3/4 as the parameter. The code that
needs to be notified about the timer interrupts would have already
registered its handler for either of the interrupts 11 to 15. I am not
sure why such remapping is used. I think it is not needed but did not
intend to change it. All this is included in the file
"arch/arm/plat-samsung/irq-vic-timer.c".

Instead of using linux irq number 11 to 15 to which consumers of timer
interrupt attach their handler, this interrupt range is moved to the
end of linux irq space used. So there will be no interrupts statically
mapped between 0 to 31.

The GIC/VIC hardware interrupts, which were previously statically
mapped to start from linux irq 32 are now moved to start from linux
irq 0. In case of exynos, GIC_ID[0] (which is SGI[0]) which was
previously at linux irq 32, will not be at linux irq 0.

This was the intended change. This was required to use Rob Herring's
GIC OF bindings patches for Exynos4.

Thanks,
Thomas.