linux-kernel - Re: simplified RISC-V interrupt and clocksource handling v2

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Date:   Thu, 02 Aug 2018 10:24:11 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...ive.com>
To:     Christoph Hellwig <hch@....de>
CC:     tglx@...utronix.de, jason@...edaemon.net, marc.zyngier@....com,
        robh+dt@...nel.org, mark.rutland@....com, anup@...infault.org,
        atish.patra@....com, devicetree@...r.kernel.org,
        aou@...s.berkeley.edu, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, shorne@...il.com
Subject:     Re: simplified RISC-V interrupt and clocksource handling v2

On Thu, 02 Aug 2018 04:49:57 PDT (-0700), Christoph Hellwig wrote:
> This series tries adds support for interrupt handling and timers
> for the RISC-V architecture.
>
> The basic per-hart interrupt handling implemented by the scause
> and sie CSRs is extremely simple and implemented directly in
> arch/riscv/kernel/irq.c.  In addition there is a irqchip driver
> for the PLIC external interrupt controller, which is called through
> the set_handle_irq API, and a clocksource driver that gets its
> timer interrupt directly from the low-level interrupt handling.
>
> Compared to previous iterations this version does not try to use an
> irqchip driver for the low-level interrupt handling.  This saves
> a couple indirect calls and an additional read of the scause CSR
> in the hot path, makes the code much simpler and last but not least
> avoid the dependency on a device tree for a mandatory architectural
> feature.
>
> A git tree is available here (contains a few more patches before
> the ones in this series)
>
>     git://git.infradead.org/users/hch/riscv.git riscv-irq-simple.2
>
> Gitweb:
>
>     http://git.infradead.org/users/hch/riscv.git/shortlog/refs/heads/riscv-irq-simple.2
>
> Changes since v1:
>  - rename the plic driver to irq-sifive-plic
>  - switch to a default compatible of sifive,plic0 (still supporting the
>    riscv,plic0 name for compatibility)
>  - add a reference for the SiFive PLIC register layout
>  - fix plic_toggle addressing for large numbers of hwirqs
>  - remove the call to ack_bad_irq
>  - use a raw spinlock for plic_toggle_lock
>  - use the irq_desc cpumask in the plic enable/disable methods
>  - add back OF contexid parsing in the plic driver
>  - don't allow COMPILE_TEST builds of the clocksource driver, as it
>    depends on <asm/sbi.h>
>  - default the clocksource driver to y
>  - clean up naming in the clocksource driver
>  - remove the MINDELTA and MAXDELTA #defines
>  - various DT binding fixes

Ah, thank you so much.  This is great!  With this patch set applied on top of 
rc7 I can boot QEMU master and get to the Fedora root file system.  I'll review 
the patch set properly, but at least for now I think a

Tested-by: Palmer Dabbelt <palmer@...ive.com>

is warranted.  What's the best way to go about merging this?  There's quite a 
bit of arch/riscv diff here so I don't mind taking it through the RISC-V tree, 
but there's also some irqchip and clocksource stuff as well so I'm not sure if 
that's OK to do.