Messages in this thread | | | Date | Sun, 11 Jul 2021 11:59:33 -0700 (PDT) | Subject | Re: [PATCH v7 1/1] RISC-V: Use SBI SRST extension when available | From | Palmer Dabbelt <> |
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On Fri, 09 Jul 2021 22:01:02 PDT (-0700), Anup Patel wrote: > > > On 08/07/21, 9:22 AM, "Anup Patel" <anup@brainfault.org> wrote: > > On Wed, Jul 7, 2021 at 1:57 AM Palmer Dabbelt <palmerdabbelt@google.com> wrote: > > > > On Mon, 21 Jun 2021 21:46:46 PDT (-0700), anup@brainfault.org wrote: > > > Hi Palmer, > > > > > > On Wed, Jun 9, 2021 at 5:43 PM Anup Patel <anup.patel@wdc.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@wdc.com> > > >> Reviewed-by: Atish Patra <atish.patra@wdc.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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