Interrupt handling for RISCV

[Hesham Almatary]

On Mon, Jun 12, 2017 at 6:01 AM, Denis Obrezkov <denisobrezkov at gmail.com> wrote:
> 2017-06-11 22:43 GMT+03:00 Hesham Almatary <heshamelmatary at gmail.com>:
>>
>> Hi Denis,
>>
>>
>>
>> On Sun, Jun 11, 2017 at 11:52 PM, Denis Obrezkov
>> <denisobrezkov at gmail.com> wrote:
>> > Hello Hesham,
>> >
>> > I found out that your code in interrupt handling routine is outdated -
>> Which interrupt handling routine? The port doesn't handle interrupts.
>> The only relevant code is enable/disable interrupts, but it doesn't
>> matter at this stage that it's outdated (as we don't have interrupts).
>>
>> > the format of mstatus and sstatus registers was changed.
>> > I can produce some patches in a few days, though, I still don't
>> > understand
>> > how to deal with local and global interrupts.
>> >
>> Could you illustrate what do you mean by "global" and "local"
>> interrupts? I still argue for a simple port that runs hello world, you
>> don't need interrupts, so this shouldn't be a blocker for you.
>>
>> > --
>> > Regards, Denis Obrezkov
>>
>>
>>
>> --
>> Hesham
>
> RISC-V has local and global interrupt sources: Privileged ISA 1.10, chapter
> 7.2.
>
Thanks for the reference. After reading this part, global interrupts
are mapped to external interrupts that are not part of RISC-V ISA.
While local interrupts are per-hart and defined/controlled by RISC-V
ISA using mstatus/mip/sip registers. For example, if you're going to
implement interrupts-based UART driver (platform/BSP specific), you'll
need global/external interrupts hence PLIC. On the other hand, when
you implement timer driver, you'll use local interrupts (RISC-V/ISA
specific).

>
>
> --
> Regards, Denis Obrezkov



-- 
Hesham