Re: [avr-gcc-list] Save RAMPZ register in interrupt handler routines

[Paulo Marques]

Quoting Anatoly Sokolov <address@hidden>:

> Hello.

Hi,

>  For FLASH memory access for 128KB avr-libc have pgm_read_*_far macros.
> These macros modify RAMPZ register and is non-reenterable. Using these
> macros in main loop/interrupts code can cause collisions of access to FLASH
> memory.
>
>  For solving of this problem I offer save RAMPZ register in interrupt
> handler routines for 128KB devices ('avr31' and 'avr51' architectures). The
> '-mno-save-rampz' switch restore old behaviour.

Wouldn't it be better to just disable interrupts / restore interrutps 
in the macros themselves? Or maybe just create _atomic variants that do 
this, or even just document that if you use pgm_read_*_far macros 
inside interrupts you have to make sure that in the main code you do 
that from atomic sections or at least with interrupts disabled...

Otherwise you will be paying a latency penalty on every interrupt call 
even when you don't need to (and that is probably most of the time).

--
Paulo Marques


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