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Message-ID: <CAAhSdy2rvi1v4Txbd18JE6pad+iW8resE8_6+7ZnNiQKUMhgkQ@mail.gmail.com>
Date: Thu, 29 Jul 2021 10:14:44 +0530
From: Anup Patel <anup@...infault.org>
To: Palmer Dabbelt <palmer@...belt.com>
Cc: Anup Patel <Anup.Patel@....com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Albert Ou <aou@...s.berkeley.edu>,
Atish Patra <Atish.Patra@....com>,
Alistair Francis <Alistair.Francis@....com>,
linux-riscv <linux-riscv@...ts.infradead.org>,
"linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 1/1] RISC-V: Use SBI SRST extension when available
On Thu, Jul 29, 2021 at 10:00 AM Palmer Dabbelt <palmer@...belt.com> wrote:
>
> On Sun, 11 Jul 2021 11:59:33 PDT (-0700), Palmer Dabbelt wrote:
> > On Fri, 09 Jul 2021 22:01:02 PDT (-0700), Anup Patel wrote:
> >>
> >>
> >> On 08/07/21, 9:22 AM, "Anup Patel" <anup@...infault.org> wrote:
> >>
> >> On Wed, Jul 7, 2021 at 1:57 AM Palmer Dabbelt <palmerdabbelt@...gle.com> wrote:
> >> >
> >> > On Mon, 21 Jun 2021 21:46:46 PDT (-0700), anup@...infault.org wrote:
> >> > > Hi Palmer,
> >> > >
> >> > > On Wed, Jun 9, 2021 at 5:43 PM Anup Patel <anup.patel@....com> wrote:
> >> > >>
> >> > >> The SBI SRST extension provides a standard way to poweroff and
> >> > >> reboot the system irrespective to whether Linux RISC-V S-mode
> >> > >> is running natively (HS-mode) or inside Guest/VM (VS-mode).
> >> > >>
> >> > >> The SBI SRST extension is available in the SBI v0.3 specification.
> >> > >> (Refer, https://github.com/riscv/riscv-sbi-doc/releases/tag/v0.3.0-rc1)
> >> > >
> >> > > Can you please consider this patch for Linux-5.14-rc1 ?
> >> > >
> >> > > The SBI v0.3 spec is already frozen and this patch has been
> >> > > floating on LKML for quite a few months now.
> >> >
> >> > I didn't realize that SBI-0.3 had been frozed. That link is to a RC,
> >> > the cooresponding v0.3.0 tag isn't in that repo. Can you give me a
> >> > pointer to the frozen spec?
> >>
> >> Here's the link to SBI v0.3.0 tag:
> >> https://github.com/riscv/riscv-sbi-doc/releases/tag/v0.3.0
> >>
> >> We treat RC tags as frozen in SBI spec because no functional
> >> changes are done in SBI spec after it is tagged as RC. We only
> >> do typo fixes and clarifications on SBI spec RC release.
> >
> > Treating the 0.3.0-rc1 as frozen as soon as it's released is a
> > terrifying policy: some of the fixes I sent in after I saw rc1 released
> > change the actual meaning of the text, even if they were meant to change
> > them to what I thought the intended meaning was supposed to be. That
> > means the actual text of 0.3.0-rc1 and 0.3.0 conflict with each other.
> > Given that frozen comes with a guarntee of backwards compatibility, does
> > that mean that the behavior allowed by 0.3.0-rc1 is compliant with the
> > SBI, even if it was likely just allowed by a wording mistake?
> >
> > If you're going to freeze things at rc1 then you really need to be quite
> > explicit about that, as generally the point of RCs is to elicit
> > review/testing. Looks like I was the only person to have provided any
> > review, so I guess I was the only one who assumed "We don't expect any
> > significant functional changes. We will wait for any further feedback
> > and release the official v0.3 in a month or so." actually meant "this is
> > frozen".
> >
> >> Can you take this patch for Linux-5.14 ??
> >
> > No, sorry, it's way too late for that. Please be specific about when
> > you freeze specifications in the future, so we can all stay on the same
> > page.
>
> I went and talked to Krste, and he says that there's a whole process for
> freezing extensions that this hasn't gone through. They don't have
> anything written down that I can point to, but can you guys please just
> get on the same page about this? It seems like every time I talk to
> someone from the RISC-V foundation I get a conflicting description of
> what's going on, and I'm entirely out of patience when it comes to
> getting blamed for all the chaos over there.
The RISC-V SBI is a pure software specification and not a ISA specification.
In fact, this is not even non-ISA specification dealing with a MMIO
(or hardware) device. There is no process defined for RISC-V software
specifications.
The last SBI v0.2 release was done by you (Palmer). At that time, you
simply tagged the SBI v0.2 release and announced it everywhere.
Regards,
Anup
>
> >
> >>
> >> Regards,
> >> Anup
> >>
> >> Regards,
> >> Anup
> >>
> >> >
> >> > >
> >> > > Regards,
> >> > > Anup
> >> > >
> >> > >>
> >> > >> This patch extends Linux RISC-V SBI implementation to detect
> >> > >> and use SBI SRST extension.
> >> > >>
> >> > >> Signed-off-by: Anup Patel <anup.patel@....com>
> >> > >> Reviewed-by: Atish Patra <atish.patra@....com>
> >> > >> ---
> >> > >> arch/riscv/include/asm/sbi.h | 24 ++++++++++++++++++++++++
> >> > >> arch/riscv/kernel/sbi.c | 35 +++++++++++++++++++++++++++++++++++
> >> > >> 2 files changed, 59 insertions(+)
> >> > >>
> >> > >> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> >> > >> index 0d42693cb65e..289621da4a2a 100644
> >> > >> --- a/arch/riscv/include/asm/sbi.h
> >> > >> +++ b/arch/riscv/include/asm/sbi.h
> >> > >> @@ -27,6 +27,7 @@ enum sbi_ext_id {
> >> > >> SBI_EXT_IPI = 0x735049,
> >> > >> SBI_EXT_RFENCE = 0x52464E43,
> >> > >> SBI_EXT_HSM = 0x48534D,
> >> > >> + SBI_EXT_SRST = 0x53525354,
> >> > >> };
> >> > >>
> >> > >> enum sbi_ext_base_fid {
> >> > >> @@ -70,6 +71,21 @@ enum sbi_hsm_hart_status {
> >> > >> SBI_HSM_HART_STATUS_STOP_PENDING,
> >> > >> };
> >> > >>
> >> > >> +enum sbi_ext_srst_fid {
> >> > >> + SBI_EXT_SRST_RESET = 0,
> >> > >> +};
> >> > >> +
> >> > >> +enum sbi_srst_reset_type {
> >> > >> + SBI_SRST_RESET_TYPE_SHUTDOWN = 0,
> >> > >> + SBI_SRST_RESET_TYPE_COLD_REBOOT,
> >> > >> + SBI_SRST_RESET_TYPE_WARM_REBOOT,
> >> > >> +};
> >> > >> +
> >> > >> +enum sbi_srst_reset_reason {
> >> > >> + SBI_SRST_RESET_REASON_NONE = 0,
> >> > >> + SBI_SRST_RESET_REASON_SYS_FAILURE,
> >> > >> +};
> >> > >> +
> >> > >> #define SBI_SPEC_VERSION_DEFAULT 0x1
> >> > >> #define SBI_SPEC_VERSION_MAJOR_SHIFT 24
> >> > >> #define SBI_SPEC_VERSION_MAJOR_MASK 0x7f
> >> > >> @@ -148,6 +164,14 @@ static inline unsigned long sbi_minor_version(void)
> >> > >> return sbi_spec_version & SBI_SPEC_VERSION_MINOR_MASK;
> >> > >> }
> >> > >>
> >> > >> +/* Make SBI version */
> >> > >> +static inline unsigned long sbi_mk_version(unsigned long major,
> >> > >> + unsigned long minor)
> >> > >> +{
> >> > >> + return ((major & SBI_SPEC_VERSION_MAJOR_MASK) <<
> >> > >> + SBI_SPEC_VERSION_MAJOR_SHIFT) | minor;
> >> > >> +}
> >> > >> +
> >> > >> int sbi_err_map_linux_errno(int err);
> >> > >> #else /* CONFIG_RISCV_SBI */
> >> > >> static inline int sbi_remote_fence_i(const unsigned long *hart_mask) { return -1; }
> >> > >> diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> >> > >> index 7402a417f38e..9a84f0cb5175 100644
> >> > >> --- a/arch/riscv/kernel/sbi.c
> >> > >> +++ b/arch/riscv/kernel/sbi.c
> >> > >> @@ -7,6 +7,7 @@
> >> > >>
> >> > >> #include <linux/init.h>
> >> > >> #include <linux/pm.h>
> >> > >> +#include <linux/reboot.h>
> >> > >> #include <asm/sbi.h>
> >> > >> #include <asm/smp.h>
> >> > >>
> >> > >> @@ -501,6 +502,32 @@ int sbi_remote_hfence_vvma_asid(const unsigned long *hart_mask,
> >> > >> }
> >> > >> EXPORT_SYMBOL(sbi_remote_hfence_vvma_asid);
> >> > >>
> >> > >> +static void sbi_srst_reset(unsigned long type, unsigned long reason)
> >> > >> +{
> >> > >> + sbi_ecall(SBI_EXT_SRST, SBI_EXT_SRST_RESET, type, reason,
> >> > >> + 0, 0, 0, 0);
> >> > >> + pr_warn("%s: type=0x%lx reason=0x%lx failed\n",
> >> > >> + __func__, type, reason);
> >> > >> +}
> >> > >> +
> >> > >> +static int sbi_srst_reboot(struct notifier_block *this,
> >> > >> + unsigned long mode, void *cmd)
> >> > >> +{
> >> > >> + sbi_srst_reset((mode == REBOOT_WARM || mode == REBOOT_SOFT) ?
> >> > >> + SBI_SRST_RESET_TYPE_WARM_REBOOT :
> >> > >> + SBI_SRST_RESET_TYPE_COLD_REBOOT,
> >> > >> + SBI_SRST_RESET_REASON_NONE);
> >> > >> + return NOTIFY_DONE;
> >> > >> +}
> >> > >> +
> >> > >> +static struct notifier_block sbi_srst_reboot_nb;
> >> > >> +
> >> > >> +static void sbi_srst_power_off(void)
> >> > >> +{
> >> > >> + sbi_srst_reset(SBI_SRST_RESET_TYPE_SHUTDOWN,
> >> > >> + SBI_SRST_RESET_REASON_NONE);
> >> > >> +}
> >> > >> +
> >> > >> /**
> >> > >> * sbi_probe_extension() - Check if an SBI extension ID is supported or not.
> >> > >> * @extid: The extension ID to be probed.
> >> > >> @@ -608,6 +635,14 @@ void __init sbi_init(void)
> >> > >> } else {
> >> > >> __sbi_rfence = __sbi_rfence_v01;
> >> > >> }
> >> > >> + if ((sbi_spec_version >= sbi_mk_version(0, 3)) &&
> >> > >> + (sbi_probe_extension(SBI_EXT_SRST) > 0)) {
> >> > >> + pr_info("SBI SRST extension detected\n");
> >> > >> + pm_power_off = sbi_srst_power_off;
> >> > >> + sbi_srst_reboot_nb.notifier_call = sbi_srst_reboot;
> >> > >> + sbi_srst_reboot_nb.priority = 192;
> >> > >> + register_restart_handler(&sbi_srst_reboot_nb);
> >> > >> + }
> >> > >> } else {
> >> > >> __sbi_set_timer = __sbi_set_timer_v01;
> >> > >> __sbi_send_ipi = __sbi_send_ipi_v01;
> >> > >> --
> >> > >> 2.25.1
> >> > >>
> >>
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