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Message-ID: <mhng-6c25dda6-4c85-447c-ad9c-7641f2858b10@palmerdabbelt-glaptop>
Date: Sun, 11 Jul 2021 11:59:33 -0700 (PDT)
From: Palmer Dabbelt <palmerdabbelt@...gle.com>
To: Anup Patel <Anup.Patel@....com>
CC: anup@...infault.org, Paul Walmsley <paul.walmsley@...ive.com>,
aou@...s.berkeley.edu, Atish Patra <Atish.Patra@....com>,
Alistair Francis <Alistair.Francis@....com>,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 1/1] RISC-V: Use SBI SRST extension when available
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.
>
> 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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