[+ Daniel, Kevin]
On Wed, May 11, 2016 at 04:37:41PM +0100, Sudeep Holla wrote:
> This patch adds appropriate callbacks to support ACPI Low Power Idle
> (LPI) on ARM64.
>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> Cc: Mark Rutland <mark.rutland@xxxxxxx>
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
> ---
> arch/arm64/kernel/acpi.c | 48 +++++++++++++++++++++++++++++++++++++++++
> drivers/firmware/psci.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 104 insertions(+)
>
> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
I think we can add this to arm64/kernel/cpuidle.c so that we have all
arch code managing idle in one place.
> index d1ce8e2f98b9..bf82ce5c8fce 100644
> --- a/arch/arm64/kernel/acpi.c
> +++ b/arch/arm64/kernel/acpi.c
> @@ -18,6 +18,7 @@
> #include <linux/acpi.h>
> #include <linux/bootmem.h>
> #include <linux/cpumask.h>
> +#include <linux/cpu_pm.h>
> #include <linux/init.h>
> #include <linux/irq.h>
> #include <linux/irqdomain.h>
> @@ -25,6 +26,9 @@
> #include <linux/of_fdt.h>
> #include <linux/smp.h>
>
> +#include <acpi/processor.h>
> +
> +#include <asm/cpuidle.h>
> #include <asm/cputype.h>
> #include <asm/cpu_ops.h>
> #include <asm/smp_plat.h>
> @@ -211,6 +215,50 @@ void __init acpi_boot_table_init(void)
> }
> }
>
> +int acpi_processor_ffh_lpi_probe(unsigned int cpu)
> +{
> + return arm_cpuidle_init(cpu);
> +}
> +
> +#define ACPI_FFH_LPI_ARM_FLAGS_CORE_CONTEXT BIT(0)
> +#define ACPI_FFH_LPI_ARM_FLAGS_TRACE_CONTEXT BIT(1)
> +#define ACPI_FFH_LPI_ARM_FLAGS_GICR_CONTEXT BIT(2)
> +#define ACPI_FFH_LPI_ARM_FLAGS_GICD_CONTEXT BIT(3)
> +#define ACPI_FFH_LPI_ARM_FLAGS_ALL_CONTEXT \
> + (ACPI_FFH_LPI_ARM_FLAGS_CORE_CONTEXT | \
> + ACPI_FFH_LPI_ARM_FLAGS_TRACE_CONTEXT | \
> + ACPI_FFH_LPI_ARM_FLAGS_GICR_CONTEXT | \
> + ACPI_FFH_LPI_ARM_FLAGS_GICD_CONTEXT)
> +
> +struct acpi_lpi_state *lpi;
> +int acpi_processor_ffh_lpi_enter(struct acpi_lpi_state *lpi, int idx)
> +{
> + int ret = 0;
> + bool save_ctx = lpi->arch_flags & ACPI_FFH_LPI_ARM_FLAGS_ALL_CONTEXT;
I am not really that keen on this, as you know. Those flags are
there to say "save these components registers". I see the CPU PM
notifiers as a way to save/restore CPU peripheral state, but
they should *not* carry out any action that affects the power
state itself, that's down to the suspend finisher (eg PSCI),
because that's where the specific idle states are managed.
I agree we have no clue whatsoever on what we *really* need
to save/restore, but that's orthogonal to what you are solving
here.
See eg gic_cpu_if_down(). Do we call it from the GIC CPU PM notifier ?
No. We should not handle the same problem differently.
On top of that, we have no way to solve this problem for DT,
all I am saying is that it is ill-defined and given that LPI
is new I'd rather we got it right from the beginning.
I am open to suggestions here.
> +
> + if (!idx) {
> + cpu_do_idle();
> + return idx;
> + }
> +
> + /* TODO cpu_pm_{enter,exit} can be done in generic code ? */
> + if (save_ctx)
> + 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);
> +
> + if (save_ctx)
> + cpu_pm_exit();
> + }
> +
> + return ret ? -1 : idx;
The body of this function (if we remove save_ctx) is identical
to arm_enter_idle_state(), it would be nice if we found a way
where to put this code and share it with the ARM CPUidle driver,
but I am not too fussed about that either.
> +}
> +
> #ifdef CONFIG_ACPI_APEI
> pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
> {
> diff --git a/drivers/firmware/psci.c b/drivers/firmware/psci.c
> index fa4ea22ca12e..e06bfee68e1d 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;
Nit: I am not sure this can happen, but you really do not want
count to become == -1.
> + if (!count)
> + 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;
> + 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;
> +}
> +#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);
> +
> cpu_node = of_get_cpu_node(cpu, NULL);
> if (!cpu_node)
> return -ENODEV;
save_ctx notwithstanding the patch is fine, let's define what to
do with that, remainder of the code is ok.
Thanks,
Lorenzo
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