[PATCH v3 06/51] cpuidle,tegra: Push RCU-idle into driver

Peter Zijlstra
2023-01-12T20:05:01Z

Doing RCU-idle outside the driver, only to then temporarily enable it
again, at least twice, before going idle is daft.

Notably once implicitly through the cpu_pm_*() calls and once
explicitly doing RCU_NONIDLE().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Ulf Hansson <ulf.hansson@linaro.org>
---
drivers/cpuidle/cpuidle-tegra.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)

--- a/drivers/cpuidle/cpuidle-tegra.c
+++ b/drivers/cpuidle/cpuidle-tegra.c
@@ -180,9 +180,11 @@ static int tegra_cpuidle_state_enter(str
}

local_fiq_disable();
- RCU_NONIDLE(tegra_pm_set_cpu_in_lp2());
+ tegra_pm_set_cpu_in_lp2();
cpu_pm_enter();

+ ct_idle_enter();
+
switch (index) {
case TEGRA_C7:
err = tegra_cpuidle_c7_enter();
@@ -197,8 +199,10 @@ static int tegra_cpuidle_state_enter(str
break;
}

+ ct_idle_exit();
+
cpu_pm_exit();
- RCU_NONIDLE(tegra_pm_clear_cpu_in_lp2());
+ tegra_pm_clear_cpu_in_lp2();
local_fiq_enable();

return err ?: index;
@@ -226,6 +230,7 @@ static int tegra_cpuidle_enter(struct cp
struct cpuidle_driver *drv,
int index)
{
+ bool do_rcu = drv->states[index].flags & CPUIDLE_FLAG_RCU_IDLE;
unsigned int cpu = cpu_logical_map(dev->cpu);
int ret;

@@ -233,9 +238,13 @@ static int tegra_cpuidle_enter(struct cp
if (dev->states_usage[index].disable)
return -1;

- if (index == TEGRA_C1)
+ if (index == TEGRA_C1) {
+ if (do_rcu)
+ ct_idle_enter();
ret = arm_cpuidle_simple_enter(dev, drv, index);
- else
+ if (do_rcu)
+ ct_idle_exit();
+ } else
ret = tegra_cpuidle_state_enter(dev, index, cpu);

if (ret < 0) {
@@ -285,7 +294,8 @@ static struct cpuidle_driver tegra_idle_
.exit_latency = 2000,
.target_residency = 2200,
.power_usage = 100,
- .flags = CPUIDLE_FLAG_TIMER_STOP,
+ .flags = CPUIDLE_FLAG_TIMER_STOP |
+ CPUIDLE_FLAG_RCU_IDLE,
.name = "C7",
.desc = "CPU core powered off",
},
@@ -295,6 +305,7 @@ static struct cpuidle_driver tegra_idle_
.target_residency = 10000,
.power_usage = 0,
.flags = CPUIDLE_FLAG_TIMER_STOP |
+ CPUIDLE_FLAG_RCU_IDLE |
CPUIDLE_FLAG_COUPLED,
.name = "CC6",
.desc = "CPU cluster powered off",