Problem with ticker.exe for or1ksim/OpenRISC BSP

[Gedare Bloom]

I see you are kind of copying the file structure of ARM. I'm not sure
this is a good example for a simple port. m68k is more
straightforward.

-Gedare

On Fri, Jul 18, 2014 at 10:17 AM, Gedare Bloom <gedare at rtems.org> wrote:
> On Fri, Jul 18, 2014 at 1:35 AM, Hesham Moustafa
> <heshamelmatary at gmail.com> wrote:
>>
>> On Thu, Jul 17, 2014 at 3:10 PM, Joel Sherrill
>> <joel.sherrill at oarcorp.com> wrote:
>> > This definitely sounds like not handling the context switch necessary
>> > part of the
>> > IRQ processing properly so always returning to IDLE. I call this a
>> > simple return.
>> >
>> > All ports have a version of this code. no_cpu should have reasonable
>> > pseudo-code.
>> > m68k is likely the easiest to read as real code.
>> >
>> > You need to do a simple return if:
>> >
>> > (a) IRQ is nested, or
>> > (b) DISPATCH_NEEDED is false
>> >
>> This is a macro that defines the address of the corresponding variable
>> within the per cpu config table right? Please correct the following if
>> I it's wrong. From assembly (when doing restore after C ISR handler is
>> executed), I have to load this variable value, check if it's true
>> (greater than zero), and if yes, jump to _ISR_Dispatch. I am a little
>> confused what context should be loaded in both cases of: simple
>> return, and _ISR_Dispatch; In case of _ISR_Dispatch, should I save
>> stack pointer and return address and other context like normal context
>> switch (function call)? While in interrupt context (simple return), I
>> am saving almost all registers with some other necessary registers
>> related to exceptions.
>>
> Please see http://rtems.org/onlinedocs/doc-current/share/rtems/html/porting/Interrupts-Interrupt-Dispatching.html#Interrupts-Interrupt-Dispatching
>
> Summarizing:
>
> You need to update a few variables before calling the user ISR:
> _Thread_Dispatch_disable_level += 1
> _ISR_Nest_level += 1
>
> And decrement them after returning.
> If ISRs are nested you do a simple return.
>
> Then you need to check if _CPU_ISR_Dispatch_disable is set, if so do a
> simple return.
>
> Then you need to check if DISPATCH_NEEDED, if so you need to do the
> ISR_Dispatch.
>
>
>> One thing I have a problem with, is when using some macros like
>> DISPATCH_NEEDED (it's a variable address right?) I am normally
>> including rtems/score/percpu.h from the assembly file (which does the
>> magic) to get these definitions but the compiler suffers. I think I
>> have to provide compiler option or something to just include #define
>> macros? If yes, where to add it?
>>
> Make sure to include rtems/asm.h before including percpu.h so you get
> the ASM defines instead of C defines, since you are (presumably)
> writing this in assembly. You could also use inline assembly, but then
> you need to use expression operands [1] to provide access to these
> variables instead.
>
> [1]  https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html
>
> -Gedare
>
>> > Otherwise, you need to some CPU specific magic to get our of the IRQ and
>> > back to the thread. Make it look like it called _Thread_Dispatch with
>> > sufficient saved registers (e.g. callee destroyed). This is usually called
>> > _ISR_Dispatch.  When the call from _ISR_Dispatch to _Thread_Dispatch
>> > returns, you do the magic needed to return tot he interrupted thread
>> > (IDLE in this case) as if nothing happened.