Re: [PATCH v6 4/5] arm64: add support for ACPI Low Power Idle(LPI)
From: Sudeep Holla
Date: Mon Jun 27 2016 - 13:08:10 EST
On 27/06/16 17:29, Daniel Lezcano wrote:
On 06/22/2016 04:17 PM, Lorenzo Pieralisi wrote:
Hi Sudeep,
On Tue, Jun 14, 2016 at 03:48:38PM +0100, Sudeep Holla wrote:
This patch adds appropriate callbacks to support ACPI Low Power Idle
(LPI) on ARM64.
Now that arm_enter_idle_state is exactly same in both generic ARM{32,64}
CPUIdle driver and ARM64 backend for ACPI processor idle driver, we can
unify it and move to cpuidle-arm.h header.
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
---
arch/arm64/kernel/cpuidle.c | 17 +++++++++++++
drivers/cpuidle/cpuidle-arm.c | 23 ++----------------
drivers/firmware/psci.c | 56
+++++++++++++++++++++++++++++++++++++++++++
include/linux/cpuidle-arm.h | 30 +++++++++++++++++++++++
4 files changed, 105 insertions(+), 21 deletions(-)
create mode 100644 include/linux/cpuidle-arm.h
This patch seems fine by me, it would be good if Daniel can have
a look too.
Some minor comments below.
[...]
diff --git a/drivers/firmware/psci.c b/drivers/firmware/psci.c
index 03e04582791c..c6caa863d156 100644
--- a/drivers/firmware/psci.c
+++ b/drivers/firmware/psci.c
@@ -13,6 +13,7 @@
#define pr_fmt(fmt) "psci: " fmt
+#include <linux/acpi.h>
#include <linux/arm-smccc.h>
#include <linux/cpuidle.h>
#include <linux/errno.h>
@@ -310,11 +311,66 @@ static int psci_dt_cpu_init_idle(struct
device_node *cpu_node, int cpu)
return ret;
}
+#ifdef CONFIG_ACPI
+#include <acpi/processor.h>
+
+static int __maybe_unused psci_acpi_cpu_init_idle(unsigned int cpu)
+{
+ int i, count;
+ u32 *psci_states;
+ struct acpi_processor *pr;
+ struct acpi_lpi_state *lpi;
+
+ pr = per_cpu(processors, cpu);
+ if (unlikely(!pr || !pr->flags.has_lpi))
+ return -EINVAL;
+
+ /*
+ * If the PSCI cpu_suspend function hook has not been initialized
+ * idle states must not be enabled, so bail out
+ */
+ if (!psci_ops.cpu_suspend)
+ return -EOPNOTSUPP;
+
+ count = pr->power.count - 1;
+ if (count <= 0)
+ return -ENODEV;
+
+ psci_states = kcalloc(count, sizeof(*psci_states), GFP_KERNEL);
+ if (!psci_states)
+ return -ENOMEM;
+
+ for (i = 0; i < count; i++) {
+ u32 state;
+
+ lpi = &pr->power.lpi_states[i + 1];
+ state = lpi->address & 0xFFFFFFFF;
Why mask 'address' if 'state' is u32 ?
Agreed, I overlooked it.
+ if (!psci_power_state_is_valid(state)) {
+ pr_warn("Invalid PSCI power state %#x\n", state);
+ kfree(psci_states);
+ return -EINVAL;
+ }
+ psci_states[i] = state;
+ }
+ /* Idle states parsed correctly, initialize per-cpu pointer */
+ per_cpu(psci_power_state, cpu) = psci_states;
+ return 0;
The ACPI and the PSCI code are not self contained here.
It would be nice to move this function to the ACPI code.
+}
+#else
+static int __maybe_unused psci_acpi_cpu_init_idle(unsigned int cpu)
+{
+ return -EINVAL;
+}
+#endif
+
int psci_cpu_init_idle(unsigned int cpu)
{
struct device_node *cpu_node;
int ret;
+ if (!acpi_disabled)
+ return psci_acpi_cpu_init_idle(cpu);
+
acpi_disabled - acpi_disabled - acpi_disabled everywhere :/
The enable-method approach is not straightforward and now it is polluted
by acpi-disabled.
So IIUC,
smp_init_cpus (contains acpi_disabled)
smp_cpu_setup
cpu_read_ops
cpu_read_enable_method (contains acpi_disabled)
acpi_get_enable_method (returns 'psci' after checking
psci_is_present)
Then psci_cpu_init_idle is called... and check again acpi_disabled.
IMO, the circumlocution with the psci vs acpi vs acpi_disabled is
getting unnecessary too complex, is prone to error and will lead to
unmaintainable code very soon.
I suggest to sort out encapsulation and self-contained code before
adding more feature in this area.
I understand your concern but I have no idea on how to clean up. Lorenzo
asked to factor our common code between psci_{dt,acpi}_cpu_init_idle and
I think you might not like the refactoring[1]. I didn't want to change
cpuidle_ops and hence psci_dt_cpu_init_idle parameters. I will see if
changing that simplifies things.
cpu_node = of_get_cpu_node(cpu, NULL);
if (!cpu_node)
return -ENODEV;
diff --git a/include/linux/cpuidle-arm.h b/include/linux/cpuidle-arm.h
new file mode 100644
index 000000000000..b99bcb3f43dd
--- /dev/null
+++ b/include/linux/cpuidle-arm.h
arm-cpuidle.h for consistency with other (ARM) include/linux files ?
@@ -0,0 +1,30 @@
+#include <linux/cpu_pm.h>
+
+#include <asm/cpuidle.h>
+
+/*
+ * arm_enter_idle_state - Programs CPU to enter the specified state
+ */
+static int arm_generic_enter_idle_state(int idx)
+{
+ int ret;
+
+ if (!idx) {
+ cpu_do_idle();
+ return idx;
+ }
+
+ ret = cpu_pm_enter();
+ if (!ret) {
+ /*
+ * Pass idle state index to cpu_suspend which in turn will
+ * call the CPU ops suspend protocol with idle index as a
+ * parameter.
+ */
+ ret = arm_cpuidle_suspend(idx);
+
+ cpu_pm_exit();
+ }
+
+ return ret ? -1 : idx;
+}
Either you do this, or we have to add it somehow somewhere in
drivers/cpuidle to avoid duplicating it.
@Daniel: do you have an opinion on this please ?
I don't like the idea to add an ARM arch specific header in
include/linux. I thought this directory was supposed to contain as much
as possible arch agnostic headers.
While I agree, but what we have is ARM specific code here and calling it
generic might not make it any usable on other architecture unless they
have the same semantics. I am fine if you and Rafael are OK with that.
May be the name can be changed to something more generic:
eg.
int cpuidle_generic_enter(int idx);
and then add an option:
HAVE_CPUIDLE_GENERIC_ENTER
, then in the generic header:
#ifdef HAVE_CPUIDLE_GENERIC_ENTER
int cpuidle_generic_enter(int idx);
#endif
, change the function name in cpuidle-arm .c
and finally add in the ARM and ARM64 Kconfig's option
HAVE_CPUIDLE_GENERIC_ENTER.
-- Daniel
[1]
http://git.kernel.org/cgit/linux/kernel/git/sudeep.holla/linux.git/commit/?h=for_review/arm64_lpi&id=9b516ad4442b4168e962ba4ca87bd568d605053b
--
Regards,
Sudeep