| Message ID | 1417678103-32571-3-git-send-email-shreyas@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
On Thu, Dec 04, 2014 at 12:58:21PM +0530, Shreyas B. Prabhu wrote: > From: "Preeti U. Murthy" <preeti@linux.vnet.ibm.com> > > The secondary threads should enter deep idle states so as to gain maximum > powersavings when the entire core is offline. To do so the offline path > must be made aware of the available deepest idle state. Hence probe the > device tree for the possible idle states in powernv core code and > expose the deepest idle state through flags. > > Since the device tree is probed by the cpuidle driver as well, move > the parameters required to discover the idle states into an appropriate > common place to both the driver and the powernv core code. > > Another point is that fastsleep idle state may require workarounds in > the kernel to function properly. This workaround is introduced in the > subsequent patches. However neither the cpuidle driver or the hotplug > path need be bothered about this workaround. > > They will be taken care of by the core powernv code. > > Originally-by: Srivatsa S. Bhat <srivatsa@mit.edu> > Signed-off-by: Preeti U. Murthy <preeti@linux.vnet.ibm.com> > Signed-off-by: Shreyas B. Prabhu <shreyas@linux.vnet.ibm.com> Reviewed-by: Paul Mackerras <paulus@samba.org>
On Thu, 2014-04-12 at 07:28:21 UTC, "Shreyas B. Prabhu" wrote: > From: "Preeti U. Murthy" <preeti@linux.vnet.ibm.com> > > The secondary threads should enter deep idle states so as to gain maximum > powersavings when the entire core is offline. To do so the offline path > must be made aware of the available deepest idle state. Hence probe the > device tree for the possible idle states in powernv core code and > expose the deepest idle state through flags. > > Since the device tree is probed by the cpuidle driver as well, move > the parameters required to discover the idle states into an appropriate > common place to both the driver and the powernv core code. > > Another point is that fastsleep idle state may require workarounds in > the kernel to function properly. This workaround is introduced in the > subsequent patches. However neither the cpuidle driver or the hotplug > path need be bothered about this workaround. > > They will be taken care of by the core powernv code. ... > diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c > index 4753958..3dc4cec 100644 > --- a/arch/powerpc/platforms/powernv/smp.c > +++ b/arch/powerpc/platforms/powernv/smp.c > @@ -159,13 +160,17 @@ static void pnv_smp_cpu_kill_self(void) > generic_set_cpu_dead(cpu); > smp_wmb(); > > + idle_states = pnv_get_supported_cpuidle_states(); > /* We don't want to take decrementer interrupts while we are offline, > * so clear LPCR:PECE1. We keep PECE2 enabled. > */ > mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) & ~(u64)LPCR_PECE1); > while (!generic_check_cpu_restart(cpu)) { > ppc64_runlatch_off(); > - power7_nap(1); > + if (idle_states & OPAL_PM_SLEEP_ENABLED) > + power7_sleep(); > + else > + power7_nap(1); So I might be missing something subtle here, but aren't we potentially enabling sleep here, prior to your next patch which makes it safe to actually use sleep? Shouldn't we only allow sleep after patch 3? Or in other words shouldn't this be patch 3 (or 4)? cheers
On Sunday 14 December 2014 03:35 PM, Michael Ellerman wrote: > On Thu, 2014-04-12 at 07:28:21 UTC, "Shreyas B. Prabhu" wrote: >> From: "Preeti U. Murthy" <preeti@linux.vnet.ibm.com> >> >> The secondary threads should enter deep idle states so as to gain maximum >> powersavings when the entire core is offline. To do so the offline path >> must be made aware of the available deepest idle state. Hence probe the >> device tree for the possible idle states in powernv core code and >> expose the deepest idle state through flags. >> >> Since the device tree is probed by the cpuidle driver as well, move >> the parameters required to discover the idle states into an appropriate >> common place to both the driver and the powernv core code. >> >> Another point is that fastsleep idle state may require workarounds in >> the kernel to function properly. This workaround is introduced in the >> subsequent patches. However neither the cpuidle driver or the hotplug >> path need be bothered about this workaround. >> >> They will be taken care of by the core powernv code. > > ... > >> diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c >> index 4753958..3dc4cec 100644 >> --- a/arch/powerpc/platforms/powernv/smp.c >> +++ b/arch/powerpc/platforms/powernv/smp.c >> @@ -159,13 +160,17 @@ static void pnv_smp_cpu_kill_self(void) >> generic_set_cpu_dead(cpu); >> smp_wmb(); >> >> + idle_states = pnv_get_supported_cpuidle_states(); >> /* We don't want to take decrementer interrupts while we are offline, >> * so clear LPCR:PECE1. We keep PECE2 enabled. >> */ >> mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) & ~(u64)LPCR_PECE1); >> while (!generic_check_cpu_restart(cpu)) { >> ppc64_runlatch_off(); >> - power7_nap(1); >> + if (idle_states & OPAL_PM_SLEEP_ENABLED) >> + power7_sleep(); >> + else >> + power7_nap(1); > > So I might be missing something subtle here, but aren't we potentially enabling > sleep here, prior to your next patch which makes it safe to actually use sleep? > > Shouldn't we only allow sleep after patch 3? Or in other words shouldn't this > be patch 3 (or 4)? > A point to note here, when sleep is exposed in device tree under ibm,cpu-idle-state-flags, we use 2 bits, OPAL_PM_SLEEP_ENABLED and OPAL_PM_SLEEP_ENABLED_ER1. This patch only enables sleep in OPAL_PM_SLEEP_ENABLED case. In current POWER8 chips, sleep is exposed as OPAL_PM_SLEEP_ENABLED_ER1, indicating the hardware bug and the need for fastsleep workaround. And bulk of the redesign introduced in next patch helps fastsleep workaround and winkle. That said, using sleep without "powernv: cpuidle: Redesign idle states management" does expose us to a bug with performing VM migration onto subcores. But not enabling here (i.e offline case) until next patch doesn't make much difference as the cpuidle framework has already enabled sleep. In other words, OPAL_PM_SLEEP_ENABLED case will come into picture when the hardware bug around fastsleep is fixed. And in this case running any kernel without "powernv: cpuidle: Redesign idle states management" does expose us to a bug with sleep + VM migration onto subcores, because cpuidle enables sleep based on OPAL_PM_SLEEP_ENABLED bit. IMO delaying enabling of sleep in OPAL_PM_SLEEP_ENABLED case until next patch, only for offline cpus should not gain us much. But I'll be happy to resend the patches with the change if you think it is required. Thanks, Shreyas
On Sun, 2014-12-14 at 17:19 +0530, Shreyas B Prabhu wrote: > > On Sunday 14 December 2014 03:35 PM, Michael Ellerman wrote: > > On Thu, 2014-04-12 at 07:28:21 UTC, "Shreyas B. Prabhu" wrote: > >> From: "Preeti U. Murthy" <preeti@linux.vnet.ibm.com> > >> > >> The secondary threads should enter deep idle states so as to gain maximum > >> powersavings when the entire core is offline. To do so the offline path > >> must be made aware of the available deepest idle state. Hence probe the > >> device tree for the possible idle states in powernv core code and > >> expose the deepest idle state through flags. > >> > >> Since the device tree is probed by the cpuidle driver as well, move > >> the parameters required to discover the idle states into an appropriate > >> common place to both the driver and the powernv core code. > >> > >> Another point is that fastsleep idle state may require workarounds in > >> the kernel to function properly. This workaround is introduced in the > >> subsequent patches. However neither the cpuidle driver or the hotplug > >> path need be bothered about this workaround. > >> > >> They will be taken care of by the core powernv code. > > > > ... > > > >> diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c > >> index 4753958..3dc4cec 100644 > >> --- a/arch/powerpc/platforms/powernv/smp.c > >> +++ b/arch/powerpc/platforms/powernv/smp.c > >> @@ -159,13 +160,17 @@ static void pnv_smp_cpu_kill_self(void) > >> generic_set_cpu_dead(cpu); > >> smp_wmb(); > >> > >> + idle_states = pnv_get_supported_cpuidle_states(); > >> /* We don't want to take decrementer interrupts while we are offline, > >> * so clear LPCR:PECE1. We keep PECE2 enabled. > >> */ > >> mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) & ~(u64)LPCR_PECE1); > >> while (!generic_check_cpu_restart(cpu)) { > >> ppc64_runlatch_off(); > >> - power7_nap(1); > >> + if (idle_states & OPAL_PM_SLEEP_ENABLED) > >> + power7_sleep(); > >> + else > >> + power7_nap(1); > > > > So I might be missing something subtle here, but aren't we potentially enabling > > sleep here, prior to your next patch which makes it safe to actually use sleep? > > > > Shouldn't we only allow sleep after patch 3? Or in other words shouldn't this > > be patch 3 (or 4)? > > A point to note here, when sleep is exposed in device tree under ibm,cpu-idle-state-flags, > we use 2 bits, OPAL_PM_SLEEP_ENABLED and OPAL_PM_SLEEP_ENABLED_ER1. This patch only enables > sleep in OPAL_PM_SLEEP_ENABLED case. In current POWER8 chips, sleep is exposed as > OPAL_PM_SLEEP_ENABLED_ER1, indicating the hardware bug and the need for fastsleep > workaround. And bulk of the redesign introduced in next patch helps fastsleep workaround > and winkle. > > That said, using sleep without "powernv: cpuidle: Redesign idle states management" > does expose us to a bug with performing VM migration onto subcores. But not enabling > here (i.e offline case) until next patch doesn't make much difference as the cpuidle > framework has already enabled sleep. > > In other words, OPAL_PM_SLEEP_ENABLED case will come into picture when the hardware > bug around fastsleep is fixed. And in this case running any kernel without "powernv: > cpuidle: Redesign idle states management" does expose us to a bug with sleep + VM > migration onto subcores, because cpuidle enables sleep based on OPAL_PM_SLEEP_ENABLED > bit. IMO delaying enabling of sleep in OPAL_PM_SLEEP_ENABLED case until next patch, > only for offline cpus should not gain us much. But I'll be happy to resend the patches > with the change if you think it is required. OK, thanks for the explanation. I'll put it in as-is. In future if you can add that sort of explanation to the changelog that would be great. cheers
diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h index 9124b0e..f8b95c0 100644 --- a/arch/powerpc/include/asm/opal.h +++ b/arch/powerpc/include/asm/opal.h @@ -155,6 +155,14 @@ struct opal_sg_list { #define OPAL_REGISTER_DUMP_REGION 101 #define OPAL_UNREGISTER_DUMP_REGION 102 +/* Device tree flags */ + +/* Flags set in power-mgmt nodes in device tree if + * respective idle states are supported in the platform. + */ +#define OPAL_PM_NAP_ENABLED 0x00010000 +#define OPAL_PM_SLEEP_ENABLED 0x00020000 + #ifndef __ASSEMBLY__ #include <linux/notifier.h> diff --git a/arch/powerpc/platforms/powernv/powernv.h b/arch/powerpc/platforms/powernv/powernv.h index 6c8e2d1..604c48e 100644 --- a/arch/powerpc/platforms/powernv/powernv.h +++ b/arch/powerpc/platforms/powernv/powernv.h @@ -29,6 +29,8 @@ static inline u64 pnv_pci_dma_get_required_mask(struct pci_dev *pdev) } #endif +extern u32 pnv_get_supported_cpuidle_states(void); + extern void pnv_lpc_init(void); bool cpu_core_split_required(void); diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c index 3f9546d..34c6665 100644 --- a/arch/powerpc/platforms/powernv/setup.c +++ b/arch/powerpc/platforms/powernv/setup.c @@ -290,6 +290,55 @@ static void __init pnv_setup_machdep_rtas(void) } #endif /* CONFIG_PPC_POWERNV_RTAS */ +static u32 supported_cpuidle_states; + +u32 pnv_get_supported_cpuidle_states(void) +{ + return supported_cpuidle_states; +} + +static int __init pnv_init_idle_states(void) +{ + struct device_node *power_mgt; + int dt_idle_states; + const __be32 *idle_state_flags; + u32 len_flags, flags; + int i; + + supported_cpuidle_states = 0; + + if (cpuidle_disable != IDLE_NO_OVERRIDE) + return 0; + + if (!firmware_has_feature(FW_FEATURE_OPALv3)) + return 0; + + power_mgt = of_find_node_by_path("/ibm,opal/power-mgt"); + if (!power_mgt) { + pr_warn("opal: PowerMgmt Node not found\n"); + return 0; + } + + idle_state_flags = of_get_property(power_mgt, + "ibm,cpu-idle-state-flags", &len_flags); + if (!idle_state_flags) { + pr_warn("DT-PowerMgmt: missing ibm,cpu-idle-state-flags\n"); + return 0; + } + + dt_idle_states = len_flags / sizeof(u32); + + for (i = 0; i < dt_idle_states; i++) { + flags = be32_to_cpu(idle_state_flags[i]); + supported_cpuidle_states |= flags; + } + + return 0; +} + +subsys_initcall(pnv_init_idle_states); + + static int __init pnv_probe(void) { unsigned long root = of_get_flat_dt_root(); diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c index 4753958..3dc4cec 100644 --- a/arch/powerpc/platforms/powernv/smp.c +++ b/arch/powerpc/platforms/powernv/smp.c @@ -149,6 +149,7 @@ static int pnv_smp_cpu_disable(void) static void pnv_smp_cpu_kill_self(void) { unsigned int cpu; + u32 idle_states; /* Standard hot unplug procedure */ local_irq_disable(); @@ -159,13 +160,17 @@ static void pnv_smp_cpu_kill_self(void) generic_set_cpu_dead(cpu); smp_wmb(); + idle_states = pnv_get_supported_cpuidle_states(); /* We don't want to take decrementer interrupts while we are offline, * so clear LPCR:PECE1. We keep PECE2 enabled. */ mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) & ~(u64)LPCR_PECE1); while (!generic_check_cpu_restart(cpu)) { ppc64_runlatch_off(); - power7_nap(1); + if (idle_states & OPAL_PM_SLEEP_ENABLED) + power7_sleep(); + else + power7_nap(1); ppc64_runlatch_on(); /* Clear the IPI that woke us up */ diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c index 7d3a349..0a7d827 100644 --- a/drivers/cpuidle/cpuidle-powernv.c +++ b/drivers/cpuidle/cpuidle-powernv.c @@ -16,13 +16,10 @@ #include <asm/machdep.h> #include <asm/firmware.h> +#include <asm/opal.h> #include <asm/runlatch.h> -/* Flags and constants used in PowerNV platform */ - #define MAX_POWERNV_IDLE_STATES 8 -#define IDLE_USE_INST_NAP 0x00010000 /* Use nap instruction */ -#define IDLE_USE_INST_SLEEP 0x00020000 /* Use sleep instruction */ struct cpuidle_driver powernv_idle_driver = { .name = "powernv_idle", @@ -198,7 +195,7 @@ static int powernv_add_idle_states(void) * target residency to be 10x exit_latency */ latency_ns = be32_to_cpu(idle_state_latency[i]); - if (flags & IDLE_USE_INST_NAP) { + if (flags & OPAL_PM_NAP_ENABLED) { /* Add NAP state */ strcpy(powernv_states[nr_idle_states].name, "Nap"); strcpy(powernv_states[nr_idle_states].desc, "Nap"); @@ -211,7 +208,7 @@ static int powernv_add_idle_states(void) nr_idle_states++; } - if (flags & IDLE_USE_INST_SLEEP) { + if (flags & OPAL_PM_SLEEP_ENABLED) { /* Add FASTSLEEP state */ strcpy(powernv_states[nr_idle_states].name, "FastSleep"); strcpy(powernv_states[nr_idle_states].desc, "FastSleep");