idle: introduce cpuidle generic module

This module will load the various lowlevel cpuidle modules' implementations
during initialiation. If it finds one available module, it will change
the global gCpuIdleFunc as its own better one.

When idle, cpuidle module will select the best cstate and enter it by
calling the lowlevel module's implementation.

Signed-off-by: Yongcong Du <ycdu.vmcore@gmail.com>
Signed-off-by: Fredrik Holmqvist <fredrik.holmqvist@gmail.com>

headers/os/drivers/cpuidle.h

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2012, Haiku, Inc. All Rights Reserved.
+ * Distributed under the terms of the MIT License.
+ */
+#ifndef _CPUIDLE_MODULE_H
+#define _CPUIDLE_MODULE_H
+
+
+#include <module.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define CPUIDLE_CSTATE_MAX	8
+#define CSTATE_NAME_LENGTH	32
+#define B_CPUIDLE_MODULE_NAME "idle/generic/cpuidle/v1"
+
+
+struct CpuidleStats {
+	uint64		usageCount;
+	bigtime_t	usageTime;
+};
+
+
+struct CpuidleInfo {
+	int32			cstateSleep;
+	CpuidleStats	stats[CPUIDLE_CSTATE_MAX];
+};
+
+
+struct CpuidleCstate {
+	char	name[CSTATE_NAME_LENGTH];
+	int32	latency;
+	int32	(*EnterIdle)(int32 state, CpuidleCstate *cstate);
+	void	*pData;
+};
+
+
+struct CpuidleModuleInfo {
+	module_info		info;
+	CpuidleCstate	cStates[CPUIDLE_CSTATE_MAX];
+	int32			cStateCount;
+};
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif		// _CPUIDLE_MODULE_H

src/add-ons/kernel/idle/Jamfile

@@ -0,0 +1,3 @@
+SubDir HAIKU_TOP src add-ons kernel idle ;
+
+SubInclude HAIKU_TOP src add-ons kernel idle generic ;

src/add-ons/kernel/idle/generic/Jamfile

@@ -0,0 +1,7 @@
+SubDir HAIKU_TOP src add-ons kernel idle generic ;
+
+UsePrivateKernelHeaders ;
+
+KernelAddon <module>cpuidle :
+	cpuidle.cpp
+	;

src/add-ons/kernel/idle/generic/cpuidle.cpp

@@ -0,0 +1,119 @@
+/*
+ * Copyright 2012, Haiku, Inc. All Rights Reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Yongcong Du <ycdu.vmcore@gmail.com>
+ */
+
+#include <KernelExport.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <smp.h>
+#include <cpuidle.h>
+
+
+static CpuidleInfo sPerCPU[B_MAX_CPU_COUNT];
+static CpuidleModuleInfo *sCpuidleModule;
+
+extern void (*gCpuIdleFunc)(void);
+
+
+/*
+ * next cstate selection algorithm is based on NetBSD's
+ * it's simple, stupid
+ */
+static int32
+SelectCstate(CpuidleInfo *info)
+{
+	static const int32 csFactor = 3;
+
+	for (int32 i = sCpuidleModule->cStateCount - 1; i > 0; i--) {
+		CpuidleCstate *cState = &sCpuidleModule->cStates[i];
+		if (info->cstateSleep > cState->latency * csFactor)
+			return i;
+	}
+
+	/* Choose C1 if there's no state found */
+	return 1;
+}
+
+
+static inline void
+EnterCstate(int32 state, CpuidleInfo *info)
+{
+	CpuidleCstate *cstate = &sCpuidleModule->cStates[state];
+	bigtime_t now = system_time();
+	if (cstate->EnterIdle(state, cstate) > 0) {
+		bigtime_t diff = system_time() - now;
+		info->cstateSleep = diff;
+		info->stats[state].usageCount++;
+		info->stats[state].usageTime += diff;
+	} else {
+		info->cstateSleep = 0;
+	}
+}
+
+
+static void
+CpuCstateIdle(void)
+{
+	CpuidleInfo *info = &sPerCPU[smp_get_current_cpu()];
+	int32 state = SelectCstate(info);
+	EnterCstate(state, info);
+}
+
+
+static status_t
+std_ops(int32 op, ...)
+{
+	switch (op) {
+		case B_MODULE_INIT:
+		{
+			dprintf("generic cpuidle init\n");
+			void *cookie = open_module_list("idle/cpuidles");
+			if (cookie == NULL)
+				return B_ERROR;
+
+			char name[B_FILE_NAME_LENGTH];
+			size_t nameLength = sizeof(name);
+
+			while (read_next_module_name(cookie, name, &nameLength) == B_OK) {
+				if (get_module(name, (module_info **)&sCpuidleModule) == B_OK) {
+					break;
+				}
+			}
+
+			close_module_list(cookie);
+			if (sCpuidleModule->cStateCount < 2) {
+				dprintf("no enough available cstates, exiting...\n");
+				put_module(sCpuidleModule->info.name);
+				return B_ERROR;
+			} else {
+				dprintf("using %s\n", sCpuidleModule->info.name);
+				gCpuIdleFunc = CpuCstateIdle;
+				return B_OK;
+			}
+		}
+		case B_MODULE_UNINIT:
+			dprintf("generic cpuidle uninit\n");
+			put_module(sCpuidleModule->info.name);
+			return B_OK;
+	}
+
+	return B_ERROR;
+}
+
+
+static module_info sModule = {
+	B_CPUIDLE_MODULE_NAME,
+	0,
+	std_ops
+};
+
+
+module_info *modules[] = {
+	(module_info *)&sModule,
+	NULL
+};