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Date: Tue, 07 Oct 2014 16:06:16 +1100
From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
To: "Shreyas B. Prabhu" <shreyas@...ux.vnet.ibm.com>
Cc: linux-kernel@...r.kernel.org,
"Srivatsa S. Bhat" <srivatsa@....edu>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>,
"Rafael J. Wysocki" <rjw@...ysocki.net>, linux-pm@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org,
"Preeti U. Murthy" <preeti@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 1/3] powerpc/powernv: Enable Offline CPUs to enter
deep idle states
On Wed, 2014-10-01 at 13:15 +0530, Shreyas B. Prabhu wrote:
> From: "Srivatsa S. Bhat" <srivatsa@....edu>
>
> The offline cpus
Arguably "cpus" here should be "secondary threads" to make the commit
message a bit more comprehensible. A few more nits below...
> 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.
>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> Cc: linux-pm@...r.kernel.org
> Cc: linuxppc-dev@...ts.ozlabs.org
> Signed-off-by: Srivatsa S. Bhat <srivatsa@....edu>
> Signed-off-by: Shreyas B. Prabhu <shreyas@...ux.vnet.ibm.com>
> [ Changelog modified by preeti@...ux.vnet.ibm.com ]
> Signed-off-by: Preeti U. Murthy <preeti@...ux.vnet.ibm.com>
> ---
> arch/powerpc/include/asm/opal.h | 4 +++
> arch/powerpc/platforms/powernv/powernv.h | 7 +++++
> arch/powerpc/platforms/powernv/setup.c | 51 ++++++++++++++++++++++++++++++++
> arch/powerpc/platforms/powernv/smp.c | 11 ++++++-
> drivers/cpuidle/cpuidle-powernv.c | 7 ++---
> 5 files changed, 75 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
> index 86055e5..28b8342 100644
> --- a/arch/powerpc/include/asm/opal.h
> +++ b/arch/powerpc/include/asm/opal.h
> @@ -772,6 +772,10 @@ extern struct kobject *opal_kobj;
> /* /ibm,opal */
> extern struct device_node *opal_node;
>
> +/* Flags used for idle state discovery from the device tree */
> +#define IDLE_INST_NAP 0x00010000 /* nap instruction can be used */
> +#define IDLE_INST_SLEEP 0x00020000 /* sleep instruction can be used */
Please provide a better explanation if what this is about, maybe a
commend describing the device-tree property. Also those macros have
names too likely to collide or be confused with other uses. Use
something a bit less ambiguous such as OPAL_PM_NAP_AVAILABLE,
OPAL_PM_SLEEP_ENABLED,...
Also put that in the part of opal.h that isn't the linux internal
implementation, but instead the "API" part. This will help when we
finally split the file.
> /* API functions */
> int64_t opal_invalid_call(void);
> int64_t opal_console_write(int64_t term_number, __be64 *length,
> diff --git a/arch/powerpc/platforms/powernv/powernv.h b/arch/powerpc/platforms/powernv/powernv.h
> index 75501bf..31ece13 100644
> --- a/arch/powerpc/platforms/powernv/powernv.h
> +++ b/arch/powerpc/platforms/powernv/powernv.h
> @@ -23,6 +23,13 @@ static inline int pnv_pci_dma_set_mask(struct pci_dev *pdev, u64 dma_mask)
> }
> #endif
>
> +/* Flags to indicate which of the CPU idle states are available for use */
> +
> +#define IDLE_USE_NAP (1UL << 0)
> +#define IDLE_USE_SLEEP (1UL << 1)
This somewhat duplicates the opal.h definitions, can't we just re-use
them ?
> +extern unsigned int 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 5a0e2dc..2dca1d8 100644
> --- a/arch/powerpc/platforms/powernv/setup.c
> +++ b/arch/powerpc/platforms/powernv/setup.c
> @@ -282,6 +282,57 @@ static void __init pnv_setup_machdep_rtas(void)
> }
> #endif /* CONFIG_PPC_POWERNV_RTAS */
>
> +static unsigned int supported_cpuidle_states;
> +
> +unsigned int pnv_get_supported_cpuidle_states(void)
> +{
> + return supported_cpuidle_states;
> +}
Will this be used by a module ? Doesn't it need to be exported ? Also
keep the prefix pnv on the variable, I don't like globals with such a
confusing name.
> +static int __init pnv_probe_idle_states(void)
> +{
> + struct device_node *power_mgt;
> + struct property *prop;
> + int dt_idle_states;
> + u32 *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;
> + }
> +
> + prop = of_find_property(power_mgt, "ibm,cpu-idle-state-flags", NULL);
> + if (!prop) {
> + pr_warn("DT-PowerMgmt: missing ibm,cpu-idle-state-flags\n");
> + return 0;
> + }
> +
> + dt_idle_states = prop->length / sizeof(u32);
> + flags = (u32 *) prop->value;
> +
> + for (i = 0; i < dt_idle_states; i++) {
> + if (flags[i] & IDLE_INST_NAP)
> + supported_cpuidle_states |= IDLE_USE_NAP;
> +
> + if (flags[i] & IDLE_INST_SLEEP)
> + supported_cpuidle_states |= IDLE_USE_SLEEP;
> + }
> +
> + return 0;
> +}
> +
> +subsys_initcall(pnv_probe_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 5fcfcf4..3ad31d2 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;
> + unsigned long idle_states;
>
> /* Standard hot unplug procedure */
> local_irq_disable();
> @@ -159,13 +160,21 @@ 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 sleep is supported, go to sleep, instead of nap */
> + if (idle_states & IDLE_USE_SLEEP)
> + power7_sleep();
> + else
> + power7_nap(1);
> +
> ppc64_runlatch_on();
>
> /* Reenable IRQs briefly to clear the IPI that woke us */
> diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
> index a64be57..23d2743 100644
> --- a/drivers/cpuidle/cpuidle-powernv.c
> +++ b/drivers/cpuidle/cpuidle-powernv.c
> @@ -16,13 +16,12 @@
>
> #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",
> @@ -185,7 +184,7 @@ static int powernv_add_idle_states(void)
> for (i = 0; i < dt_idle_states; i++) {
>
> flags = be32_to_cpu(idle_state_flags[i]);
> - if (flags & IDLE_USE_INST_NAP) {
> + if (flags & IDLE_INST_NAP) {
> /* Add NAP state */
> strcpy(powernv_states[nr_idle_states].name, "Nap");
> strcpy(powernv_states[nr_idle_states].desc, "Nap");
> @@ -196,7 +195,7 @@ static int powernv_add_idle_states(void)
> nr_idle_states++;
> }
>
> - if (flags & IDLE_USE_INST_SLEEP) {
> + if (flags & IDLE_INST_SLEEP) {
> /* Add FASTSLEEP state */
> strcpy(powernv_states[nr_idle_states].name, "FastSleep");
> strcpy(powernv_states[nr_idle_states].desc, "FastSleep");
--
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