linux-kernel - Re: [PATCH v3 8/9] tty: Add SBI debug console support to HVC SBI driver

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Message-ID: <CAAhSdy1T-Ca7V21SSW=UCByujv39te7wRYGm40ZqDQ-JxH6pbA@mail.gmail.com>
Date:   Fri, 17 Nov 2023 18:41:23 +0530
From:   Anup Patel <anup@...infault.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Anup Patel <apatel@...tanamicro.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Atish Patra <atishp@...shpatra.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        Conor Dooley <conor@...nel.org>,
        Andrew Jones <ajones@...tanamicro.com>, kvm@...r.kernel.org,
        kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
        linux-serial@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, Atish Patra <atishp@...osinc.com>
Subject: Re: [PATCH v3 8/9] tty: Add SBI debug console support to HVC SBI driver

On Sat, Oct 21, 2023 at 10:16 PM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> On Fri, Oct 20, 2023 at 12:51:39PM +0530, Anup Patel wrote:
> > From: Atish Patra <atishp@...osinc.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@...osinc.com>
> > Signed-off-by: Anup Patel <apatel@...tanamicro.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, which
> > diff --git a/drivers/tty/hvc/hvc_riscv_sbi.c b/drivers/tty/hvc/hvc_riscv_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 = {
> > +static const struct hv_ops hvc_sbi_v01_ops = {
> >       .get_chars = hvc_sbi_tty_get,
> >       .put_chars = 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 = page_to_phys(vmalloc_to_page(buf)) + offset_in_page(buf);
> > +             if (PAGE_SIZE < (offset_in_page(buf) + count))
> > +                     count = PAGE_SIZE - offset_in_page(buf);
> > +     } else {
> > +             pa = __pa(buf);
> > +     }
> > +
> > +     if (IS_ENABLED(CONFIG_32BIT))
> > +             ret = sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_WRITE,
> > +                             count, lower_32_bits(pa), upper_32_bits(pa),
> > +                             0, 0, 0);
> > +     else
> > +             ret = sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_WRITE,
> > +                             count, pa, 0, 0, 0, 0);
>
> Again, you need a helper function here to keep you from having to keep
> this all in sync.

Sure, I will update.

>
> > +     if (ret.error)
> > +             return 0;
> > +
> > +     return count;
> >  }
> > -device_initcall(hvc_sbi_init);
> >
> > -static int __init hvc_sbi_console_init(void)
> > +static int hvc_sbi_dbcn_tty_get(uint32_t vtermno, char *buf, int count)
> >  {
> > -     hvc_instantiate(0, 0, &hvc_sbi_ops);
> > +     phys_addr_t pa;
> > +     struct sbiret ret;
> > +
> > +     if (is_vmalloc_addr(buf)) {
> > +             pa = page_to_phys(vmalloc_to_page(buf)) + offset_in_page(buf);
> > +             if (PAGE_SIZE < (offset_in_page(buf) + count))
> > +                     count = PAGE_SIZE - offset_in_page(buf);
> > +     } else {
> > +             pa = __pa(buf);
> > +     }
> > +
> > +     if (IS_ENABLED(CONFIG_32BIT))
> > +             ret = sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_READ,
> > +                             count, lower_32_bits(pa), upper_32_bits(pa),
> > +                             0, 0, 0);
> > +     else
> > +             ret = sbi_ecall(SBI_EXT_DBCN, SBI_EXT_DBCN_CONSOLE_READ,
> > +                             count, pa, 0, 0, 0, 0);
>
> And here too.

Okay.

>
> thanks,
>
> greg k-h

Regards,
Anup