[Bug 1001456] HAL misses Interrupt Clear-Pending Registers handling: wasted processing power

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--- Comment #17 from Bernard Fouché <bernard.fouche@kuantic.com> 2012-02-23 09:05:21 GMT ---
If you have at hand "The definitive guide to the ARM Cortex-M3" by Joseph Yiu:
see chapter 7, "Interrupt Inputs and Pending Behavior" section,  especially
figure 7.13, this is exactly what I observed.

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--- Comment #17 from Bernard Fouché <bernard.fouche@kuantic.com> 2012-02-23 09:05:21 GMT ---
If you have at hand "The definitive guide to the ARM Cortex-M3" by Joseph Yiu:
see chapter 7, "Interrupt Inputs and Pending Behavior" section,  especially
figure 7.13, this is exactly what I observed.

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--- Comment #18 from Ilija Kocho <ilijak@siva.com.mk> 2012-02-23 09:58:31 GMT ---
(In reply to comment #17)
> If you have at hand "The definitive guide to the ARM Cortex-M3" by Joseph Yiu:
> see chapter 7, "Interrupt Inputs and Pending Behavior" section,  especially
> figure 7.13, this is exactly what I observed.

I guess that in context of this bug you probably mean fig 7.14. (i guess the
number at the bottom of fig.).

For solution I would return to cyg_drv_interrupt_acknowledge() since that's
what it's supposed to do: "Perform any processing required at the interrupt
controller and in the CPU to cancel the current interrupt request on the
vector. An ISR may also need to program the hardware of the device to prevent
an immediate re-triggering of the interrupt."
Only, it should be called later than it is called now. I acknowledge your
concern about generic serial driver but it has some conditional code already so
adding little-bit more wouldn't harm (or IMO the impact will be lower than
adding functions on Kernel level).

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