[lowrisc-dev] PCR Interrupts

Francesco Viggiano francesco.vgg at gmail.com
Sat Jul 23 04:18:53 BST 2016


Thank you guys! I got it.

Also, Does this current untethered version support Linux kernel modules? I
am trying to use modules with "insmod" but it states that relocation is not
supported. Is there any way to install modules in this version?

Thank you,

Francesco

On Thu, Jul 21, 2016 at 1:40 PM Alex Bradbury <asb at asbradbury.org> wrote:

> On 21 July 2016 at 18:32, Wei Song <ws327 at cam.ac.uk> wrote:
> > Hello Francesco,
> >
> > The interrupt sources are simply or-reduced and connected to the irq pin
> of
> > each core.
> > There is an enable register (per core in PCR) which can be used to
> disable
> > certain interrupt source.
> > If a core decide to enable a source and response, it can read the pending
> > register in pcr (if level triggered) or poll actual devices to find out
> the
> > outstanding interrupts.
> > If level-triggered, core needs to handle interrupt directly with the
> source
> > device until the device withdraw its interrupt.
> >
> > I would say it is better to use a level triggered interrupt.
> > Edge triggered interrupt may need special hardware treatment.
> >
> > We will add a proper interrupt controller in the next code release.
>
> To clarify, this interrupt controller will be the PLIC described in
> the 1.9 draft privileged spec
> https://riscv.org/wp-content/uploads/2016/07/riscv-privileged-v1.9-1.pdf
>
> The slides+video from Krste's talk at the 4th RISC-V Workshop last
> week will hopefully go online soon, which outlines the principles
> behind this interrupt controller. For now you'll have to make do with
> the spec and my notes
> (
> http://www.lowrisc.org/blog/2016/07/notes-from-the-fourth-risc-v-workshop/
> )
> from the presentation. Krste describes the concept of an interrupt
> "gateway" that abstracts away differences between edge vs level
> triggered interrupts as they enter the PLIC. This is described in
> section 7.4 of the 1.9 RISC-V privileged spec.
>
> Best,
>
> Alex
>
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| Francesco Viggiano,  Columbia University, Staff associate researcher at
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| Phone: +1 646-9829-535, Skype ID: francesco.vgg |
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