[RFC,v2,3/3] cpuidle/powernv: save-restore sprs in opal

From: Abhishek Goel <huntbag@linux.vnet.ibm.com>

This patch moves the saving and restoring of sprs for P9 cpuidle
from kernel to opal.
In an attempt to make the powernv idle code backward compatible,
and to some extent forward compatible, add support for pre-stop entry
and post-stop exit actions in OPAL. If a kernel knows about this
opal call, then just a firmware supporting newer hardware is required,
instead of waiting for kernel updates.

Signed-off-by: Abhishek Goel <huntbag@linux.vnet.ibm.com>
Signed-off-by: Akshay Adiga <akshay.adiga@linux.vnet.ibm.com>
---
Changes from v1 :
 - Code is rebased on Nick Piggin's v4 patch "powerpc/64s: reimplement book3s
   idle code in C"
 - Set a global variable "request_opal_call" to indicate that deep
   states should make opal_call.
 - All the states that loses hypervisor states will be handled by OPAL
 - All the decision making such as identifying first thread in
   the core and taking locks before restoring in such cases have also been
   moved to OPAL
 arch/powerpc/include/asm/opal-api.h           |  4 +-
 arch/powerpc/include/asm/opal.h               |  3 +
 arch/powerpc/include/asm/processor.h          |  3 +-
 arch/powerpc/kernel/idle_book3s.S             |  6 +-
 arch/powerpc/platforms/powernv/idle.c         | 88 +++++++++++++------
 .../powerpc/platforms/powernv/opal-wrappers.S |  2 +
 6 files changed, 77 insertions(+), 29 deletions(-)

+ devicetree mail list

On 10/11/18 06:22, Akshay Adiga wrote:
> From: Abhishek Goel <huntbag@linux.vnet.ibm.com>
> 
> This patch moves the saving and restoring of sprs for P9 cpuidle
> from kernel to opal.
> In an attempt to make the powernv idle code backward compatible,
> and to some extent forward compatible, add support for pre-stop entry
> and post-stop exit actions in OPAL. If a kernel knows about this
> opal call, then just a firmware supporting newer hardware is required,
> instead of waiting for kernel updates.
> 
> Signed-off-by: Abhishek Goel <huntbag@linux.vnet.ibm.com>
> Signed-off-by: Akshay Adiga <akshay.adiga@linux.vnet.ibm.com>
> ---
> Changes from v1 :
>  - Code is rebased on Nick Piggin's v4 patch "powerpc/64s: reimplement book3s
>    idle code in C"
>  - Set a global variable "request_opal_call" to indicate that deep
>    states should make opal_call.
>  - All the states that loses hypervisor states will be handled by OPAL
>  - All the decision making such as identifying first thread in
>    the core and taking locks before restoring in such cases have also been
>    moved to OPAL
>  arch/powerpc/include/asm/opal-api.h           |  4 +-
>  arch/powerpc/include/asm/opal.h               |  3 +
>  arch/powerpc/include/asm/processor.h          |  3 +-
>  arch/powerpc/kernel/idle_book3s.S             |  6 +-
>  arch/powerpc/platforms/powernv/idle.c         | 88 +++++++++++++------
>  .../powerpc/platforms/powernv/opal-wrappers.S |  2 +
>  6 files changed, 77 insertions(+), 29 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/opal-api.h b/arch/powerpc/include/asm/opal-api.h
> index 8365353330b4..93ea1f79e295 100644
> --- a/arch/powerpc/include/asm/opal-api.h
> +++ b/arch/powerpc/include/asm/opal-api.h
> @@ -210,7 +210,9 @@
>  #define OPAL_PCI_GET_PBCQ_TUNNEL_BAR		164
>  #define OPAL_PCI_SET_PBCQ_TUNNEL_BAR		165
>  #define	OPAL_NX_COPROC_INIT			167
> -#define OPAL_LAST				167
> +#define OPAL_IDLE_SAVE				170
> +#define OPAL_IDLE_RESTORE			171
> +#define OPAL_LAST				171
>  
>  #define QUIESCE_HOLD			1 /* Spin all calls at entry */
>  #define QUIESCE_REJECT			2 /* Fail all calls with OPAL_BUSY */
> diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
> index ff3866473afe..26995e16171e 100644
> --- a/arch/powerpc/include/asm/opal.h
> +++ b/arch/powerpc/include/asm/opal.h
> @@ -356,6 +356,9 @@ extern int opal_handle_hmi_exception(struct pt_regs *regs);
>  extern void opal_shutdown(void);
>  extern int opal_resync_timebase(void);
>  
> +extern int opal_cpuidle_save(u64 psscr);
> +extern int opal_cpuidle_restore(u64 psscr, u64 srr1);
> +
>  extern void opal_lpc_init(void);
>  
>  extern void opal_kmsg_init(void);
> diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
> index 822d3236ad7f..26fa6c1836f4 100644
> --- a/arch/powerpc/include/asm/processor.h
> +++ b/arch/powerpc/include/asm/processor.h
> @@ -510,7 +510,8 @@ static inline unsigned long get_clean_sp(unsigned long sp, int is_32)
>  
>  /* asm stubs */
>  extern unsigned long isa300_idle_stop_noloss(unsigned long psscr_val);
> -extern unsigned long isa300_idle_stop_mayloss(unsigned long psscr_val);
> +extern unsigned long isa300_idle_stop_mayloss(unsigned long psscr_val,
> +						bool request_opal_call);
>  extern unsigned long isa206_idle_insn_mayloss(unsigned long type);
>  
>  extern unsigned long cpuidle_disable;
> diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
> index ffdee1ab4388..a2014d152035 100644
> --- a/arch/powerpc/kernel/idle_book3s.S
> +++ b/arch/powerpc/kernel/idle_book3s.S
> @@ -52,14 +52,16 @@ _GLOBAL(isa300_idle_stop_noloss)
>  _GLOBAL(isa300_idle_stop_mayloss)
>  	mtspr 	SPRN_PSSCR,r3
>  	std	r1,PACAR1(r13)
> -	mflr	r4
> +	mflr	r7
>  	mfcr	r5
>  	/* use stack red zone rather than a new frame */
>  	addi	r6,r1,-INT_FRAME_SIZE
>  	SAVE_GPR(2, r6)
>  	SAVE_NVGPRS(r6)
> -	std	r4,_LINK(r6)
> +	std	r7,_LINK(r6)
>  	std	r5,_CCR(r6)
> +	cmpwi	r4,0
> +	bne	opal_cpuidle_save
>  	PPC_STOP
>  	b	.	/* catch bugs */
>  
> diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
> index 681a23a066bb..bcfe08022e65 100644
> --- a/arch/powerpc/platforms/powernv/idle.c
> +++ b/arch/powerpc/platforms/powernv/idle.c
> @@ -171,6 +171,7 @@ static void pnv_fastsleep_workaround_apply(void *info)
>  
>  static bool power7_fastsleep_workaround_entry = true;
>  static bool power7_fastsleep_workaround_exit = true;
> +static bool request_opal_call = false;
>  
>  /*
>   * Used to store fastsleep workaround state
> @@ -604,6 +605,7 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
>  	unsigned long mmcr0 = 0;
>  	struct p9_sprs sprs;
>  	bool sprs_saved = false;
> +	bool is_hv_loss = false;
>  
>  	memset(&sprs, 0, sizeof(sprs));
>  
> @@ -648,7 +650,9 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
>  		  */
>  		mmcr0		= mfspr(SPRN_MMCR0);
>  	}
> -	if ((psscr & PSSCR_RL_MASK) >= pnv_first_hv_loss_level) {
> +
> +	is_hv_loss = (psscr & PSSCR_RL_MASK) >= pnv_first_hv_loss_level;
> +	if (is_hv_loss && (!request_opal_call)) {
>  		sprs.lpcr	= mfspr(SPRN_LPCR);
>  		sprs.hfscr	= mfspr(SPRN_HFSCR);
>  		sprs.fscr	= mfspr(SPRN_FSCR);
> @@ -674,7 +678,8 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
>  		atomic_start_thread_idle();
>  	}
>  
> -	srr1 = isa300_idle_stop_mayloss(psscr);
> +	srr1 = isa300_idle_stop_mayloss(psscr,
> +			is_hv_loss && request_opal_call);
>  
>  #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
>  	local_paca->requested_psscr = 0;
> @@ -685,6 +690,25 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
>  	WARN_ON_ONCE(!srr1);
>  	WARN_ON_ONCE(mfmsr() & (MSR_IR|MSR_DR));
>  
> +	/*
> +	 * On POWER9, SRR1 bits do not match exactly as expected.
> +	 * SRR1_WS_GPRLOSS (10b) can also result in SPR loss, so
> +	 * always test PSSCR if there is any state loss.
> +	 */
> +	if (likely(((psscr & PSSCR_PLS) >> 60) < pnv_first_hv_loss_level)) {
> +		if (sprs_saved)
> +			atomic_stop_thread_idle();
> +		goto out;
> +	}
> +
> +	if (request_opal_call) {
> +		opal_cpuidle_restore(psscr, srr1);
> +		goto opal_return;
> +	}
> +
> +	/* HV state loss */
> +	BUG_ON(!sprs_saved);
> +
>  	if ((srr1 & SRR1_WAKESTATE) != SRR1_WS_NOLOSS) {
>  		unsigned long mmcra;
>  
> @@ -712,19 +736,6 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
>  	if (unlikely((srr1 & SRR1_WAKEMASK_P8) == SRR1_WAKEHMI))
>  		hmi_exception_realmode(NULL);
>  
> -	/*
> -	 * On POWER9, SRR1 bits do not match exactly as expected.
> -	 * SRR1_WS_GPRLOSS (10b) can also result in SPR loss, so
> -	 * always test PSSCR if there is any state loss.
> -	 */
> -	if (likely((psscr & PSSCR_RL_MASK) < pnv_first_hv_loss_level)) {
> -		if (sprs_saved)
> -			atomic_stop_thread_idle();
> -		goto out;
> -	}
> -
> -	/* HV state loss */
> -	BUG_ON(!sprs_saved);
>  
>  	atomic_lock_thread_idle();
>  
> @@ -771,6 +782,7 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
>  
>  	mtspr(SPRN_SPRG3,	local_paca->sprg_vdso);
>  
> +opal_return:
>  	if (!radix_enabled())
>  		__slb_restore_bolted_realmode();
>  
> @@ -1284,6 +1296,7 @@ static int pnv_parse_cpuidle_dt(void)
>  	u32 *temp_u32;
>  	u64 *temp_u64;
>  	const char **temp_string;
> +	bool fall_back_to_opal = false;
>  
>  	np = of_find_node_by_path("/ibm,opal/power-mgt");
>  	if (!np) {
> @@ -1396,23 +1409,48 @@ static int pnv_parse_cpuidle_dt(void)
>  	/* Parse each child node with appropriate parser_fn */
>  	for_each_child_of_node(np1, dt_node) {
>  		bool found_known_version = false;
> -		/* we don't have state falling back to opal*/
> -		for (i = 0; i < nr_known_versions ; i++) {
> -			if (of_device_is_compatible(dt_node, known_versions[i].name)) {
> -				rc = known_versions[i].parser_fn(dt_node);
> +		if (!fall_back_to_opal) {
> +			/* we don't have state falling back to opal*/
> +			for (i = 0; i < nr_known_versions ; i++) {
> +				if (of_device_is_compatible(dt_node, known_versions[i].name)) {
> +					rc = known_versions[i].parser_fn(dt_node);
> +					if (rc) {
> +						pr_err("%s could not parse\n", known_versions[i].name);
> +						continue;
> +					}
> +					found_known_version = true;
> +				}
> +			}
> +		}
> +
> +		/*
> +		 * If any previous state falls back to opal_call
> +		 * Then all futher states will either call opal_call
> +		 * or not be included for cpuidle/cpuoffline.
> +		 *
> +		 * Moreover, having any intermediate state with no
> +		 * kernel support or opal support can be potentially
> +		 * dangerous, as hardware can potentially wakeup from
> +		 * that state. Hence, no futher states are added to
> +		 * to cpuidle/cpuoffline
> +		 */
> +		if (!found_known_version || fall_back_to_opal) {
> +			if (of_device_is_compatible(dt_node, "opal-support")) {
> +				rc = known_versions[0].parser_fn(dt_node);
>  				if (rc) {
> -					pr_err("%s could not parse\n", known_versions[i].name);
> +					pr_err("%s could not parse\n", "opal-support");
>  					continue;
>  				}
> -				found_known_version = true;
> +				fall_back_to_opal = true;
> +			} else {
> +				pr_info("Unsupported state, skipping all further state\n");
> +				goto out;
>  			}
>  		}
> -		if (!found_known_version) {
> -			pr_info("Unsupported state, skipping all further state\n");
> -			goto out;
> -		}
>  		nr_pnv_idle_states++;
>  	}
> +	if (fall_back_to_opal)
> +		request_opal_call = true;
>  out:
>  	kfree(temp_u32);
>  	kfree(temp_u64);
> diff --git a/arch/powerpc/platforms/powernv/opal-wrappers.S b/arch/powerpc/platforms/powernv/opal-wrappers.S
> index 251528231a9e..7a039a81a67e 100644
> --- a/arch/powerpc/platforms/powernv/opal-wrappers.S
> +++ b/arch/powerpc/platforms/powernv/opal-wrappers.S
> @@ -331,3 +331,5 @@ OPAL_CALL(opal_pci_set_pbcq_tunnel_bar,		OPAL_PCI_SET_PBCQ_TUNNEL_BAR);
>  OPAL_CALL(opal_sensor_read_u64,			OPAL_SENSOR_READ_U64);
>  OPAL_CALL(opal_sensor_group_enable,		OPAL_SENSOR_GROUP_ENABLE);
>  OPAL_CALL(opal_nx_coproc_init,			OPAL_NX_COPROC_INIT);
> +OPAL_CALL(opal_cpuidle_save,			OPAL_IDLE_SAVE);
> +OPAL_CALL(opal_cpuidle_restore,			OPAL_IDLE_RESTORE);
>