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Message-ID: <CAK9=C2Vg8O_6OaND_s1MhpBHpm1petoU7DNXOOaSOxXYUY1iAw@mail.gmail.com>
Date: Fri, 20 Oct 2023 19:17:03 +0530
From: Anup Patel <apatel@...tanamicro.com>
To: Andrew Jones <ajones@...tanamicro.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>,
Atish Patra <atishp@...shpatra.org>,
Palmer Dabbelt <palmer@...belt.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jirislaby@...nel.org>,
Conor Dooley <conor@...nel.org>, 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 Fri, Oct 20, 2023 at 4:16 PM Andrew Jones <ajones@...tanamicro.com> 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))
>
> I thought checkpatch complained about uppercase constants being on the
> left in comparisons.
Nope checkpatch does not complain about this.
>
> > + 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);
> > + if (ret.error)
> > + return 0;
> > +
> > + return count;
>
> Shouldn't we return ret.value here in case it's less than count? I see we
> already do that below in get().
Ahh, yes. Good catch, I will update.
>
> > }
> > -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);
> > + if (ret.error)
> > + return 0;
> > +
> > + return ret.value;
> > +}
> > +
> > +static const struct hv_ops hvc_sbi_dbcn_ops = {
> > + .put_chars = hvc_sbi_dbcn_tty_put,
> > + .get_chars = hvc_sbi_dbcn_tty_get,
> > +};
> > +
> > +static int __init hvc_sbi_init(void)
> > +{
> > + int err;
> > +
> > + if ((sbi_spec_version >= sbi_mk_version(2, 0)) &&
> > + (sbi_probe_extension(SBI_EXT_DBCN) > 0)) {
> > + err = PTR_ERR_OR_ZERO(hvc_alloc(0, 0, &hvc_sbi_dbcn_ops, 16));
>
> Why an outbuf size of only 16?
The output buffer size of 16 is a very common choice across
HVC drivers. The next best choice is 256.
I guess 256 is better so I will go with that.
>
> > + if (err)
> > + return err;
> > + hvc_instantiate(0, 0, &hvc_sbi_dbcn_ops);
> > + } else {
> > + if (IS_ENABLED(CONFIG_RISCV_SBI_V01)) {
> > + err = PTR_ERR_OR_ZERO(hvc_alloc(0, 0, &hvc_sbi_v01_ops, 16));
> > + if (err)
> > + return err;
> > + hvc_instantiate(0, 0, &hvc_sbi_v01_ops);
> > + } else {
> > + return -ENODEV;
> > + }
> > + }
> >
> > return 0;
> > }
> > -console_initcall(hvc_sbi_console_init);
> > +device_initcall(hvc_sbi_init);
> > --
> > 2.34.1
> >
>
> Thanks,
> drew
Regards,
Anup
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