[PATCH v8 5/7] qcom: cpuidle: Add cpuidle driver for QCOM cpus

Lina Iyer
2014-10-07T21:41:44Z

Add cpuidle driver interface to allow cpus to go into C-States. Use the
cpuidle DT interface, common across ARM architectures, to provide the
C-State information to the cpuidle framework.

Supported modes at this time are Standby and Standalone Power Collapse.

Signed-off-by: Lina Iyer <lina.iyer@linaro.org>
---
.../bindings/arm/msm/qcom,idle-state.txt | 81 ++++++++++++++++++++++
drivers/cpuidle/Kconfig.arm | 7 ++
drivers/cpuidle/Makefile | 1 +
drivers/cpuidle/cpuidle-qcom.c | 79 +++++++++++++++++++++
4 files changed, 168 insertions(+)
create mode 100644 Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt
create mode 100644 drivers/cpuidle/cpuidle-qcom.c

diff --git a/Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt b/Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt
new file mode 100644
index 0000000..87f1742
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt
@@ -0,0 +1,81 @@
+QCOM Idle States for cpuidle driver
+
+ARM provides idle-state node to define the cpuidle states, as defined in [1].
+cpuidle-qcom is the cpuidle driver for Qualcomm SoCs and uses these idle
+states. Idle states have different enter/exit latency and residency values.
+The idle states supported by the QCOM SoC are defined as -
+
+ * Standby
+ * Retention
+ * Standalone Power Collapse (Standalone PC or SPC)
+ * Power Collapse (PC)
+
+Standby: Standby does a little more in addition to architectural clock gating.
+When the WFI instruction is executed the ARM core would gate its internal
+clocks. In addition to gating the clocks, QCOM cpus use this instruction as a
+trigger to execute the SPM state machine. The SPM state machine waits for the
+interrupt to trigger the core back in to active. This triggers the cache
+heirarchy to enter standby states, when all cpus are idle. An interrupt brings
+the SPM state machine out of its wait, the next step is to ensure that the
+cache heirarchy is also out of standby, and then the cpu is allowed to resume
+execution.
+
+Retention: Retention is a low power state where the core is clock gated and
+the memory and the registers associated with the core are retained. The
+voltage may be reduced to the minimum value needed to keep the processor
+registers active. The SPM should be configured to execute the retention
+sequence and would wait for interrupt, before restoring the cpu to execution
+state. Retention may have a slightly higher latency than Standby.
+
+Standalone PC: A cpu can power down and warmboot if there is a sufficient time
+between the time it enters idle and the next known wake up. SPC mode is used
+to indicate a core entering a power down state without consulting any other
+cpu or the system resources. This helps save power only on that core. The SPM
+sequence for this idle state is programmed to power down the supply to the
+core, wait for the interrupt, restore power to the core, and ensure the
+system state including cache hierarchy is ready before allowing core to
+resume. Applying power and resetting the core causes the core to warmboot
+back into Elevation Level (EL) which trampolines the control back to the
+kernel. Entering a power down state for the cpu, needs to be done by trapping
+into a EL. Failing to do so, would result in a crash enforced by the warm boot
+code in the EL for the SoC. On SoCs with write-back L1 cache, the cache has to
+be flushed in s/w, before powering down the core.
+
+Power Collapse: This state is similar to the SPC mode, but distinguishes
+itself in that the cpu acknowledges and permits the SoC to enter deeper sleep
+modes. In a hierarchical power domain SoC, this means L2 and other caches can
+be flushed, system bus, clocks - lowered, and SoC main XO clock gated and
+voltages reduced, provided all cpus enter this state. Since the span of low
+power modes possible at this state is vast, the exit latency and the residency
+of this low power mode would be considered high even though at a cpu level,
+this essentially is cpu power down. The SPM in this state also may handshake
+with the Resource power manager processor in the SoC to indicate a complete
+application processor subsystem shut down.
+
+The idle-state for QCOM SoCs are distinguished by the compatible property of
+the idle-states device node.
+The devicetree representation of the idle state should be -
+
+Required properties:
+
+- compatible: Must be one of -
+ "qcom,idle-state-stby",
+ "qcom,idle-state-ret",
+ "qcom,idle-state-spc",
+ "qcom,idle-state-pc",
+ and "arm,idle-state".
+
+Other required and optional properties are specified in [1].
+
+Example:
+
+ idle-states {
+ CPU_SPC: spc {
+ compatible = "qcom,idle-state-spc", "arm,idle-state";
+ entry-latency-us = <150>;
+ exit-latency-us = <200>;
+ min-residency-us = <2000>;
+ };
+ };
+
+[1]. Documentation/devicetree/bindings/arm/idle-states.txt
diff --git a/drivers/cpuidle/Kconfig.arm b/drivers/cpuidle/Kconfig.arm
index 38cff69..6a9ee12 100644
--- a/drivers/cpuidle/Kconfig.arm
+++ b/drivers/cpuidle/Kconfig.arm
@@ -62,3 +62,10 @@ config ARM_MVEBU_V7_CPUIDLE
depends on ARCH_MVEBU
help
Select this to enable cpuidle on Armada 370, 38x and XP processors.
+
+config ARM_QCOM_CPUIDLE
+ bool "CPU Idle drivers for Qualcomm processors"
+ depends on QCOM_PM
+ select DT_IDLE_STATES
+ help
+ Select this to enable cpuidle for QCOM processors
diff --git a/drivers/cpuidle/Makefile b/drivers/cpuidle/Makefile
index 4d177b9..6c222d5 100644
--- a/drivers/cpuidle/Makefile
+++ b/drivers/cpuidle/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_ARM_ZYNQ_CPUIDLE) += cpuidle-zynq.o
obj-$(CONFIG_ARM_U8500_CPUIDLE) += cpuidle-ux500.o
obj-$(CONFIG_ARM_AT91_CPUIDLE) += cpuidle-at91.o
obj-$(CONFIG_ARM_EXYNOS_CPUIDLE) += cpuidle-exynos.o
+obj-$(CONFIG_ARM_QCOM_CPUIDLE) += cpuidle-qcom.o

###############################################################################
# MIPS drivers
diff --git a/drivers/cpuidle/cpuidle-qcom.c b/drivers/cpuidle/cpuidle-qcom.c
new file mode 100644
index 0000000..0a65065
--- /dev/null
+++ b/drivers/cpuidle/cpuidle-qcom.c
@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2014, Linaro Limited.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/cpu_pm.h>
+#include <linux/cpuidle.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#include <soc/qcom/pm.h>
+#include "dt_idle_states.h"
+
+static void (*qcom_idle_enter)(enum pm_sleep_mode);
+
+static int qcom_lpm_enter_stby(struct cpuidle_device *dev,
+ struct cpuidle_driver *drv, int index)
+{
+ qcom_idle_enter(PM_SLEEP_MODE_STBY);
+ local_irq_enable();
+
+ return index;
+}
+
+static int qcom_lpm_enter_spc(struct cpuidle_device *dev,
+ struct cpuidle_driver *drv, int index)
+{
+ cpu_pm_enter();
+ qcom_idle_enter(PM_SLEEP_MODE_SPC);
+ cpu_pm_exit();
+ local_irq_enable();
+
+ return index;
+}
+
+static struct cpuidle_driver qcom_cpuidle_driver = {
+ .name = "qcom_cpuidle",
+};
+
+static const struct of_device_id qcom_idle_state_match[] = {
+ { .compatible = "qcom,idle-state-stby", .data = qcom_lpm_enter_stby},
+ { .compatible = "qcom,idle-state-spc", .data = qcom_lpm_enter_spc },
+ { },
+};
+
+static int qcom_cpuidle_probe(struct platform_device *pdev)
+{
+ struct cpuidle_driver *drv = &qcom_cpuidle_driver;
+ int ret;
+
+ qcom_idle_enter = pdev->dev.platform_data;
+ if (!qcom_idle_enter)
+ return -EFAULT;
+
+ /* Probe for other states, including standby */
+ ret = dt_init_idle_driver(drv, qcom_idle_state_match, 0);
+ if (ret < 0)
+ return ret;
+
+ return cpuidle_register(drv, NULL);
+}
+
+static struct platform_driver qcom_cpuidle_plat_driver = {
+ .probe = qcom_cpuidle_probe,
+ .driver = {
+ .name = "qcom_cpuidle",
+ },
+};
+
+module_platform_driver(qcom_cpuidle_plat_driver);
--
1.9.1