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SubjectRe: [PATCH V4 2/3] dt-bindings: update riscv plic compatible string
On Sun, Oct 17, 2021 at 12:31 AM Heiko Stuebner <heiko@sntech.de> wrote:
>
> Am Samstag, 16. Oktober 2021, 14:56:51 CEST schrieb Guo Ren:
> > On Sat, Oct 16, 2021 at 6:35 PM Heiko Stuebner <heiko@sntech.de> wrote:
> > >
> > > Hi Guo,
> > >
> > > Am Samstag, 16. Oktober 2021, 05:21:59 CEST schrieb guoren@kernel.org:
> > > > From: Guo Ren <guoren@linux.alibaba.com>
> > > >
> > > > Add the compatible string "thead,c900-plic" to the riscv plic
> > > > bindings to support allwinner d1 SOC which contains c906 core.
> > >
> > > The compatible strings sound good now, but some things below
> > >
> > > >
> > > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> > > > Cc: Rob Herring <robh@kernel.org>
> > > > Cc: Palmer Dabbelt <palmerdabbelt@google.com>
> > > > Cc: Anup Patel <anup@brainfault.org>
> > > > Cc: Atish Patra <atish.patra@wdc.com>
> > > >
> > > > ---
> > > >
> > > > Changes since V4:
> > > > - Update description in errata style
> > > > - Update enum suggested by Anup, Heiko, Samuel
> > > >
> > > > Changes since V3:
> > > > - Rename "c9xx" to "c900"
> > > > - Add thead,c900-plic in the description section
> > > > ---
> > > > .../interrupt-controller/sifive,plic-1.0.0.yaml | 11 ++++++++++-
> > > > 1 file changed, 10 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/interrupt-controller/sifive,plic-1.0.0.yaml b/Documentation/devicetree/bindings/interrupt-controller/sifive,plic-1.0.0.yaml
> > > > index 08d5a57ce00f..272f29540135 100644
> > > > --- a/Documentation/devicetree/bindings/interrupt-controller/sifive,plic-1.0.0.yaml
> > > > +++ b/Documentation/devicetree/bindings/interrupt-controller/sifive,plic-1.0.0.yaml
> > > > @@ -35,6 +35,12 @@ description:
> > > > contains a specific memory layout, which is documented in chapter 8 of the
> > > > SiFive U5 Coreplex Series Manual <https://static.dev.sifive.com/U54-MC-RVCoreIP.pdf>.
> > > >
> > > > + The C9xx PLIC does not comply with the interrupt claim/completion process defined
> > > > + by the RISC-V PLIC specification because C9xx PLIC will mask an IRQ when it is
> > > > + claimed by PLIC driver (i.e. readl(claim) and the IRQ will be unmasked upon
> > > > + completion by PLIC driver (i.e. writel(claim). This behaviour breaks the handling
> > > > + of IRQS_ONESHOT by the generic handle_fasteoi_irq() used in the PLIC driver.
> > > > +
> > > > maintainers:
> > > > - Sagar Kadam <sagar.kadam@sifive.com>
> > > > - Paul Walmsley <paul.walmsley@sifive.com>
> > > > @@ -46,7 +52,10 @@ properties:
> > > > - enum:
> > > > - sifive,fu540-c000-plic
> > > > - canaan,k210-plic
> > > > - - const: sifive,plic-1.0.0
> > > > + - enmu:
> > >
> > > ^ spelling enum
> > >
> > > > + - sifive,plic-1.0.0
> > > > + - thead,c900-plic
> > > > + - allwinner,sun20i-d1-plic
> > >
> > > but in general I'd think that you want something like
> > >
> > > compatible:
> > > oneOf:
> > > - items:
> > > - enum:
> > > - sifive,fu540-c000-plic
> > > - canaan,k210-plic
> > > - const: sifive,plic-1.0.0
> > > - items:
> > > - enum:
> > > - allwinner,sun20i-d1-plic
> > > - const: thead,c900-plic
> > >
> > > Having only one item list would allow as valid combinations like
> > > "sifive,fu540-c000-plic", "thead,c900-plic" when checking the schema.
> > >
> > > With the oneOf and separate lists we can make sure that such
> > > "illegal" combinations get flagged by the dtbs_check
> > >
> > > [the enum with the single allwinner entry already leaves
> > > room for later addition to the c900-plic variant]
> > Thx, I'll fix it in the next version.
> >
> > another question: Is the allwinner_sun20i_d1_plic needed to IRQCHIP_DECLARE?
> >
> > +IRQCHIP_DECLARE(thead_c900_plic, "thead,c900-plic", thead_c900_plic_init);
> > +IRQCHIP_DECLARE(allwinner_sun20i_d1_plic, "allwinner,sun20i-d1-plic",
> > thead_c900_plic_init);
>
> Doing
> IRQCHIP_DECLARE(thead_c900_plic, "thead,c900-plic", thead_c900_plic_init);
> should be enough for now.
>
> Compatible-parsing happens from left to right, from most-specific to
> most-generic. So having the allwinner-d1 compatible in there is sort of a
> safeguard.
>
> If at some _later point in time_ , some specific new quirk of the D1
> implementation comes to light, we can _then_ just add a
> IRQCHIP_DECLARE(allwinner_d1_plic, "allwinner,sun20i-d1-plic", allwinner_d1_plic_init);
>
> Devicetrees should be stable and newer kernels should work with old
> devicetrees, so having the soc-specific compatible in there just makes it
> future proof :-)
Nice tip, thx.

>
>
> Heiko
>
>


--
Best Regards
Guo Ren

ML: https://lore.kernel.org/linux-csky/

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