[PATCH] riscv: add SBI SUSP extension support

[Conor Dooley]

Hey Woody,

On Thu, Jul 20, 2023 at 08:23:19AM +0800, Woody Zhang wrote:
> RISC-V SBI spec 2.0 [1] introduces System Suspend Extension which can be
> used to suspend the platform via SBI firmware.
> 
> This patch can be tested on Qemu with recent OpenSBI with
> `system-suspend-test` enabled like [2] in DTB.
> 
> [1] https://github.com/riscv-non-isa/riscv-sbi-doc/blob/master/riscv-sbi.adoc
> [2] https://github.com/woodyzhang666/qemu/commit/e4a5120133c1dc354e6ac437ec1f870f6c0f6d05
> 
> Signed-off-by: Woody Zhang <woodylab at foxmail.com>
> ---
>  arch/riscv/include/asm/sbi.h | 10 ++++++++++
>  arch/riscv/kernel/sbi.c      | 26 ++++++++++++++++++++++++++

There's prior art here, that is seemingly more complete:
https://lore.kernel.org/all/20230118180338.6484-2-ajones@ventanamicro.com/
IIRC, the reason it is still in RFC status is that the 2.0 SBI spec is
not yet frozen, so this cannot be merged.

Thanks,
Conor.

>  2 files changed, 36 insertions(+)
> 
> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> index 5b4a1bf5f439..3b04016da671 100644
> --- a/arch/riscv/include/asm/sbi.h
> +++ b/arch/riscv/include/asm/sbi.h
> @@ -30,6 +30,7 @@ enum sbi_ext_id {
>  	SBI_EXT_HSM = 0x48534D,
>  	SBI_EXT_SRST = 0x53525354,
>  	SBI_EXT_PMU = 0x504D55,
> +	SBI_EXT_SUSP = 0x53555350,
>  
>  	/* Experimentals extensions must lie within this range */
>  	SBI_EXT_EXPERIMENTAL_START = 0x08000000,
> @@ -236,6 +237,15 @@ enum sbi_pmu_ctr_type {
>  /* Flags defined for counter stop function */
>  #define SBI_PMU_STOP_FLAG_RESET (1 << 0)
>  
> +enum sbi_ext_susp_fid {
> +	SBI_EXT_SUSP_SYSTEM_SUSPEND = 0,
> +};
> +
> +/* SBI suspend sleep types */
> +enum sbi_susp_sleep_type {
> +	SBI_SUSP_SLEEP_TYPE_SUSPEND = 0x0,
> +};
> +
>  #define SBI_SPEC_VERSION_DEFAULT	0x1
>  #define SBI_SPEC_VERSION_MAJOR_SHIFT	24
>  #define SBI_SPEC_VERSION_MAJOR_MASK	0x7f
> diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> index c672c8ba9a2a..9a68959f9f18 100644
> --- a/arch/riscv/kernel/sbi.c
> +++ b/arch/riscv/kernel/sbi.c
> @@ -9,8 +9,10 @@
>  #include <linux/init.h>
>  #include <linux/pm.h>
>  #include <linux/reboot.h>
> +#include <linux/suspend.h>
>  #include <asm/sbi.h>
>  #include <asm/smp.h>
> +#include <asm/suspend.h>
>  
>  /* default SBI version is 0.1 */
>  unsigned long sbi_spec_version __ro_after_init = SBI_SPEC_VERSION_DEFAULT;
> @@ -520,6 +522,26 @@ static void sbi_srst_power_off(void)
>  		       SBI_SRST_RESET_REASON_NONE);
>  }
>  
> +static int sbi_system_suspend(unsigned long arg,
> +		unsigned long resume_entry, unsigned long context)
> +{
> +	struct sbiret ret = {0};
> +
> +	ret = sbi_ecall(SBI_EXT_SUSP, SBI_EXT_SUSP_SYSTEM_SUSPEND,
> +			SBI_SUSP_SLEEP_TYPE_SUSPEND, resume_entry, context, 0, 0, 0);
> +	return ret.error;
> +}
> +
> +static int sbi_system_suspend_enter(suspend_state_t state)
> +{
> +	return cpu_suspend(0, sbi_system_suspend);
> +}
> +
> +static const struct platform_suspend_ops sbi_suspend_ops = {
> +	.valid          = suspend_valid_only_mem,
> +	.enter          = sbi_system_suspend_enter,
> +};
> +
>  /**
>   * sbi_probe_extension() - Check if an SBI extension ID is supported or not.
>   * @extid: The extension ID to be probed.
> @@ -624,6 +646,10 @@ void __init sbi_init(void)
>  			sbi_srst_reboot_nb.priority = 192;
>  			register_restart_handler(&sbi_srst_reboot_nb);
>  		}
> +		if (sbi_probe_extension(SBI_EXT_SUSP)) {
> +			pr_info("SBI SUSP extension detected\n");
> +			suspend_set_ops(&sbi_suspend_ops);
> +		}
>  	} else {
>  		__sbi_set_timer = __sbi_set_timer_v01;
>  		__sbi_send_ipi	= __sbi_send_ipi_v01;
> -- 
> 2.39.2
> 
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