[RFC PATCH 1/1] riscv: sbi: Introduce system suspend support
Conor Dooley
conor at kernel.org
Tue Jan 10 14:23:00 PST 2023
Hey Drew!
On Fri, Jan 06, 2023 at 12:32:16PM +0100, Andrew Jones wrote:
> When the SUSP SBI extension is present it implies that the standard
> "suspend to RAM" type is available. Wire it up to the generic
> platform suspend support, also applying the already present support
> for non-retentive CPU suspend. When the kernel is built with
> CONFIG_SUSPEND, one can do 'echo mem > /sys/power/state' to suspend.
> Resumption will occur when a platform-specific wake-up event arrives.
>
> Signed-off-by: Andrew Jones <ajones at ventanamicro.com>
First things first, anything SBI depends on !m-mode, so you've gotta add
some sort of gating unfortunately around those ECALLs. But I figure you
may have already seen the build failures on patchwork for nommu?
Also, when there's an actual spec would you mind doing a Link: spec.pdf?
> ---
> arch/riscv/Kconfig | 5 ++++-
> arch/riscv/include/asm/sbi.h | 9 ++++++++
> arch/riscv/kernel/suspend.c | 41 ++++++++++++++++++++++++++++++++++++
> 3 files changed, 54 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index e2b656043abf..a53d94c1953e 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -52,7 +52,7 @@ config RISCV
> select CLONE_BACKWARDS
> select CLINT_TIMER if !MMU
> select COMMON_CLK
> - select CPU_PM if CPU_IDLE
> + select CPU_PM if (SUSPEND || CPU_IDLE)
> select EDAC_SUPPORT
> select GENERIC_ARCH_TOPOLOGY
> select GENERIC_ATOMIC64 if !64BIT
> @@ -686,6 +686,9 @@ config PORTABLE
> select OF
> select MMU
>
> +config ARCH_SUSPEND_POSSIBLE
> + def_bool y
Since the content you're adding depends on having an SBI extention,
does this need to be s/y/RISCV_SBI/?
> menu "Power management options"
>
> source "kernel/power/Kconfig"
> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> index 4ca7fbacff42..9834ba4ce3e4 100644
> --- a/arch/riscv/include/asm/sbi.h
> +++ b/arch/riscv/include/asm/sbi.h
> @@ -29,6 +29,7 @@ enum sbi_ext_id {
> SBI_EXT_RFENCE = 0x52464E43,
> SBI_EXT_HSM = 0x48534D,
> SBI_EXT_SRST = 0x53525354,
> + SBI_EXT_SUSP = 0x53555350,
> SBI_EXT_PMU = 0x504D55,
>
> /* Experimentals extensions must lie within this range */
> @@ -113,6 +114,14 @@ enum sbi_srst_reset_reason {
> SBI_SRST_RESET_REASON_SYS_FAILURE,
> };
>
> +enum sbi_ext_susp_fid {
> + SBI_EXT_SUSP_SUSPEND = 0,
> +};
> +
> +enum sbi_ext_susp_sleep_type {
> + SBI_SUSP_SLEEP_TYPE_SUSPEND = 0,
> +};
> +
> enum sbi_ext_pmu_fid {
> SBI_EXT_PMU_NUM_COUNTERS = 0,
> SBI_EXT_PMU_COUNTER_GET_INFO,
> diff --git a/arch/riscv/kernel/suspend.c b/arch/riscv/kernel/suspend.c
> index 9ba24fb8cc93..bc26e9ae4782 100644
> --- a/arch/riscv/kernel/suspend.c
> +++ b/arch/riscv/kernel/suspend.c
> @@ -4,8 +4,12 @@
> * Copyright (c) 2022 Ventana Micro Systems Inc.
> */
>
> +#define pr_fmt(fmt) "suspend: " fmt
> +
> #include <linux/ftrace.h>
> +#include <linux/suspend.h>
> #include <asm/csr.h>
> +#include <asm/sbi.h>
> #include <asm/suspend.h>
>
> static void suspend_save_csrs(struct suspend_context *context)
> @@ -85,3 +89,40 @@ int cpu_suspend(unsigned long arg,
>
> return rc;
> }
And then from here down needs to be #ifdef RISCV_SBI?
Anyways, probably stating the obvious on an RFC, but ¯\_(ツ)_/¯
Thanks,
Conor.
> +
> +static int sbi_system_suspend(unsigned long sleep_type,
> + unsigned long resume_addr,
> + unsigned long opaque)
> +{
> + struct sbiret ret;
> +
> + ret = sbi_ecall(SBI_EXT_SUSP, SBI_EXT_SUSP_SUSPEND,
> + sleep_type, resume_addr, opaque, 0, 0, 0);
> + if (ret.error)
> + return sbi_err_map_linux_errno(ret.error);
> +
> + return ret.value;
> +}
> +
> +static int sbi_system_suspend_enter(suspend_state_t state)
> +{
> + return cpu_suspend(SBI_SUSP_SLEEP_TYPE_SUSPEND, sbi_system_suspend);
> +}
> +
> +static const struct platform_suspend_ops sbi_system_suspend_ops = {
> + .valid = suspend_valid_only_mem,
> + .enter = sbi_system_suspend_enter,
> +};
> +
> +static int __init sbi_system_suspend_init(void)
> +{
> + if (!sbi_spec_is_0_1() && sbi_probe_extension(SBI_EXT_SUSP) > 0) {
> + pr_info("SBI SUSP extension detected\n");
> + if (IS_ENABLED(CONFIG_SUSPEND))
> + suspend_set_ops(&sbi_system_suspend_ops);
> + }
> +
> + return 0;
> +}
> +
> +arch_initcall(sbi_system_suspend_init);
> --
> 2.39.0
>
>
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>
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