Re: [PATCH v6 1/2] riscv-platform-spec: PLIC and CLINT for Linux-2022 platform


Abner Chang
 



Atish Patra <Atish.Patra@...> 於 2021年6月5日 週六 上午3:14寫道:
On Sat, 2021-05-29 at 22:42 +0800, Abner Chang wrote:
> From: Abner Chang <renba.chang@...>
>
> Initial description of PLIC  CLINT section of Linux-2022 platform.
>
> On v6 commit,
>   Remove the changes in Embedded-2022 section.
>
> On v5 commit,
> - Remove CLINT from platform spec
> - Require ACLINT on Linux2020 platform and have a link to   
> https://github.com/riscv/riscv-aclint/blob/master/riscv-aclint.adoc.
> - Remove Machine mode timer from previous patch because that is in
> the scope of ACLINT
> - For Embedded-2022 platform, mention Machine mode timer and refer to
> ACLINT for the definition of registers
>
> On v4 commit,
> - PLIC section with [DEPRECATED] in Linux- 2022 chapter
> - CLINT section in Linux- 2022 chapter for M-mode timer. We don't
> mention
>   IPI because AIA already supported it.
> - In Embedded-2022 Machine mode timer section, CLINT is not
> mandatory.
> - Separate section in appendix for the Machine mode timer registers
>
> On v3 commit,
> - Address review comments.
>
> On v2 commit,
> - CLINT is not deprecated.
>
> - Add a standalone section for Machine Mode Timer in System
> Peripherals.
>   Do you think this is a good place for Machine Mode Timer?
>   @Mayuresh, please check if you are ok with this change, not sure if
> this
>   overlaps with your text or not (The timer setion). I can remove
> this
>   if you prefer to put this with your patch.
>
> - In Embedded-2022, refer to Machine Mode Timer in System Peripherals
>   section and CLINT in Linux-2022 Platform.
>   @Alistair, is this ok?
>
> On v1 commit,
> - Not sure where to put the [DEPRECATED].
> - Change the reference of PLIC in section 2.2.2. Interrupt Controller
> to
>   1.1.3.2 PLIC + CLINT section.
>
> Signed-off-by: Abner Chang <renba.chang@...>
> Cc: Alistair Francis <alistair.francis@...>
> Cc: Sunil V L <sunilvl@...>
> Cc: Mayuresh Chitale <mchitale@...>
> ---
>  riscv-platform-spec.adoc | 25 ++++++++++++++++++++-----
>  1 file changed, 20 insertions(+), 5 deletions(-)
>
> diff --git a/riscv-platform-spec.adoc b/riscv-platform-spec.adoc
> index 160c74a..c0ee75d 100644
> --- a/riscv-platform-spec.adoc
> +++ b/riscv-platform-spec.adoc
> @@ -49,9 +49,24 @@ include::profiles.adoc[]
>  * Start Address
>  
>  ==== Interrupt Controller
> -* AIA
> -* PLIC + CLINT
> -* Interrupt Assignments
> +===== AIA[[AIA]]
> +===== PLIC[DEPRECATED][[PLIC]]
> +The Platform Level Interrupt Controller (PLIC) provides facilities
> to route
> +the non-local interrupts to the external interrupt of a hart context
> +with a given privilege mode in a given hart. The number of non-local
> interrupt
> +sources supported by PLIC and how does each of them connect to the
> hart
> +context is PLIC core implementation-specific. +
> +(Refer to   
> https://github.com/riscv/riscv-plic-spec/blob/master/riscv-plic.adoc[RISC-V
>  PLIC Specification]

IIRC, PLIC spec was never reviewed widely. As this group is more active
now, tt would be good to send it as a separate patch so we can do a
detailed review of that as well.
Hi Atish,
Do you mean to send the patch of PLIC spec on  https://github.com/riscv/riscv-plic-spec/blob/master/riscv-plic.adoc?


I am just concerned about semantics rather than technical details.

> +for the implementation reference of PLIC operation parameters)
> +
> +===== ACLINT
> +Linux-2020 platform 

We have now official names for the PLATFORM spec. We should refer to
that.
Yes, it's fair.

Abner

> requires the Advanced Core Local Interruptor (ACLINT,
> +refer to
> + 
> https://github.com/riscv/riscv-aclint/blob/master/riscv-aclint.adoc[RISC-V
>  ACLINT Specification])
> +to provide facilities to route inter-processor interrupt and Machine
> mode timer
> +interrupt to each RISC-V processor hart.
> +

> +===== Interrupt Assignments
>  
>  ==== System Peripherals
>  * UART/Serial Console
> @@ -289,8 +304,8 @@ Any RISC-V system that uses at least RV32/64G can
> meet the Embedded-2022
>  specification.
>  
>  ==== Interrupt Controller
> -Embedded systems are recommended to use a spec compliant
> -https://github.com/riscv/riscv-plic-spec[PLIC], a spec compliant
> +Embedded systems are recommended to use a spec compliant
> <<PLIC,PLIC>>,
> +a spec compliant
>  
> https://github.com/riscv/riscv-fast-interrupt/blob/master/clic.adoc[CLIC]
>  or both a CLIC and and PLIC.
>  

--
Regards,
Atish

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