[PATCH] riscv: add SBI SUSP extension support

[Woody Zhang]

On Thu, Jul 20, 2023 at 07:31:42AM +0100, Conor Dooley wrote:
>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.
>

OK. I didn't notice that. Drop this patch then.

Woody

>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
>>