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From:   Tomasz Jeznach <tjeznach@rivosinc.com>
Date:   Wed, 19 Jul 2023 14:43:51 -0700
Message-ID: <CAH2o1u5pZQ6iKThFLgnn+_BBZ=j8fu91URYYxwWbfVt3OyerAA@mail.gmail.com>
Subject: Re: [PATCH 01/11] RISC-V: drivers/iommu: Add RISC-V IOMMU - Ziommu support.
To:     Conor Dooley <conor@kernel.org>
Cc:     Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Anup Patel <apatel@ventanamicro.com>,
        Albert Ou <aou@eecs.berkeley.edu>, linux@rivosinc.com,
        linux-kernel@vger.kernel.org, Sebastien Boeuf <seb@rivosinc.com>,
        iommu@lists.linux.dev, Palmer Dabbelt <palmer@dabbelt.com>,
        Nick Kossifidis <mick@ics.forth.gr>,
        linux-riscv@lists.infradead.org
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On Wed, Jul 19, 2023 at 1:50=E2=80=AFPM Conor Dooley <conor@kernel.org> wro=
te:
>
> Hey Tomasz,
>
> On Wed, Jul 19, 2023 at 12:33:45PM -0700, Tomasz Jeznach wrote:
> > The patch introduces skeleton IOMMU device driver implementation as def=
ined
>
> This commit message reads like a cover letter IMO. At whatever point
> you send a v2, could you re-write this focusing on what is done in the
> patch itself?
>

ack. will amend the commit message.


> Also, since I am not going to reply to any of these iommu driver patches
> in a meaningful capacity, please run checkpatch.pl on your work. There
> are well over 100 style etc complaints that it has highlighted. Sparse
> has also gone a bit nuts, with many warnings along the lines of:
> drivers/iommu/riscv/iommu.c:1568:29: warning: incorrect type in assignmen=
t (different base types)
> drivers/iommu/riscv/iommu.c:1568:29:    expected unsigned long long [user=
type] iohgatp
> drivers/iommu/riscv/iommu.c:1568:29:    got restricted __le64 [usertype]
>
> I can provide you the full list when the patchwork automation has run
> through the series.
>

Thank you, a list of used lint checkers definitely would help.


> Anyway, what I wanted to ask was whether it was valid to use the IOMMU
> in a system if Ziommu is not present in whatever the ISA extension
> communication mechanism is? Eg, riscv,isa or the ISA string property in
> the ACPI tables.
>

Yes, this has been pointed out to me already. As far as I can recall,
there was a discussion
at some point to introduce those as Ziommu extensions, later agreeing
not to call IOMMU
using ISA string conventions.  Will remove remaining occurrences of
Ziommu from the series.


> Thanks,
> Conor.
>
> > References:
> >  - [1] https://github.com/riscv-non-isa/riscv-iommu
> >  - [2] https://github.com/tjeznach/linux/tree/tjeznach/riscv-iommu
> >  - [3] https://github.com/tjeznach/qemu/tree/tjeznach/riscv-iommu
>
> FYI, we have the Link: tag/trailer for this.
>


Thanks,
- Tomasz