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References: <20231020072140.900967-1-apatel@ventanamicro.com>
 <20231020072140.900967-9-apatel@ventanamicro.com> <87mswdbot2.fsf@all.your.base.are.belong.to.us>
In-Reply-To: <87mswdbot2.fsf@all.your.base.are.belong.to.us>
From:   Anup Patel <apatel@ventanamicro.com>
Date:   Fri, 20 Oct 2023 15:36:25 +0530
Message-ID: <CAK9=C2XrDCpq6cGCJu2CVowiksxunGwfF4JxwEZ_k85+3bU1+Q@mail.gmail.com>
Subject: Re: [PATCH v3 8/9] tty: Add SBI debug console support to HVC SBI driver
To:     =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Atish Patra <atishp@atishpatra.org>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        Conor Dooley <conor@kernel.org>,
        Andrew Jones <ajones@ventanamicro.com>, kvm@vger.kernel.org,
        kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org,
        linux-serial@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org, Atish Patra <atishp@rivosinc.com>
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On Fri, Oct 20, 2023 at 3:25=E2=80=AFPM Bj=C3=B6rn T=C3=B6pel <bjorn@kernel=
.org> wrote:
>
> Anup Patel <apatel@ventanamicro.com> writes:
>
> > From: Atish Patra <atishp@rivosinc.com>
> >
> > RISC-V SBI specification supports advanced debug console
> > support via SBI DBCN extension.
> >
> > Extend the HVC SBI driver to support it.
> >
> > Signed-off-by: Atish Patra <atishp@rivosinc.com>
> > Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> > ---
> >  drivers/tty/hvc/Kconfig         |  2 +-
> >  drivers/tty/hvc/hvc_riscv_sbi.c | 82 ++++++++++++++++++++++++++++++---
> >  2 files changed, 76 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/tty/hvc/Kconfig b/drivers/tty/hvc/Kconfig
> > index 4f9264d005c0..6e05c5c7bca1 100644
> > --- a/drivers/tty/hvc/Kconfig
> > +++ b/drivers/tty/hvc/Kconfig
> > @@ -108,7 +108,7 @@ config HVC_DCC_SERIALIZE_SMP
> >
> >  config HVC_RISCV_SBI
> >       bool "RISC-V SBI console support"
> > -     depends on RISCV_SBI_V01
> > +     depends on RISCV_SBI
> >       select HVC_DRIVER
> >       help
> >         This enables support for console output via RISC-V SBI calls, w=
hich
> > diff --git a/drivers/tty/hvc/hvc_riscv_sbi.c b/drivers/tty/hvc/hvc_risc=
v_sbi.c
> > index 31f53fa77e4a..56da1a4b5aca 100644
> > --- a/drivers/tty/hvc/hvc_riscv_sbi.c
> > +++ b/drivers/tty/hvc/hvc_riscv_sbi.c
> > @@ -39,21 +39,89 @@ static int hvc_sbi_tty_get(uint32_t vtermno, char *=
buf, int count)
> >       return i;
> >  }
> >
> > -static const struct hv_ops hvc_sbi_ops =3D {
> > +static const struct hv_ops hvc_sbi_v01_ops =3D {
> >       .get_chars =3D hvc_sbi_tty_get,
> >       .put_chars =3D hvc_sbi_tty_put,
> >  };
> >
> > -static int __init hvc_sbi_init(void)
> > +static int hvc_sbi_dbcn_tty_put(uint32_t vtermno, const char *buf, int=
 count)
> >  {
> > -     return PTR_ERR_OR_ZERO(hvc_alloc(0, 0, &hvc_sbi_ops, 16));
> > +     phys_addr_t pa;
> > +     struct sbiret ret;
> > +
> > +     if (is_vmalloc_addr(buf)) {
> > +             pa =3D page_to_phys(vmalloc_to_page(buf)) + offset_in_pag=
e(buf);
> > +             if (PAGE_SIZE < (offset_in_page(buf) + count))
> > +                     count =3D PAGE_SIZE - offset_in_page(buf);
>
> Thanks for fixing the cross-page issue. Now you're cutting the buffer
> off. What about doing two SBI calls instead? (Dito on the get side)

We don't need to handle that because the hvc_console framework
will ensure remaining characters are sent-out. Same applies to
get side as well.

Regards,
Anup