linux-kernel - Re: [RFC PATCH 1/5] RISC-V: Make IPI triggering flexible

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Date:   Sat, 29 Sep 2018 12:36:03 +0530
From:   Anup Patel <anup@...infault.org>
To:     Palmer Dabbelt <palmer@...ive.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        Atish Patra <atish.patra@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-riscv@...ts.infradead.org
Subject: Re: [RFC PATCH 1/5] RISC-V: Make IPI triggering flexible

On Sat, Sep 29, 2018 at 7:15 AM Palmer Dabbelt <palmer@...ive.com> wrote:
>
> On Mon, 10 Sep 2018 06:34:18 PDT (-0700), Christoph Hellwig wrote:
> > On Thu, Sep 06, 2018 at 04:15:14PM +0530, Anup Patel wrote:
> >> This patch is doing two things:
> >> 1. Allow IRQCHIP driver to provide IPI trigger mechanism
> >
> > And the big questions is why do we want that?  The last thing we
> > want is for people to "innovate" on how they deliver IPIs.  RISC-V
> > has defined an SBI interface for it to hide all the details, and
> > we should not try to handle systems that are not SBI compliant.
> >
> > Eventuall we might want to revisit the SBI to improve on shortcomings
> > if there are any, but we should not allow random irqchip drivers to
> > override this.
>
> I agree.  The whole point of the SBI is to provide an interface that everyone
> uses so we can the go figure out how to make this fast later.  If each platform
> has their own magic IPI hooks then this will end up being a mess.
>
> We've got some schemes floating around to make the SBI fast (essentially an SBI
> VDSO), I'd prefer to push on that rather than adding a bunch of complexity
> here.

Yes, I have already removed the IPI triggering part from this patchset.

Regards,
Anup