ARM: OMAP2+: CM: prepare for use of cm_ll_data function pointers

There are several CM operations which behave similarly across OMAP2+
SoCs, but which have slight differences in their underlying
implementations.

This patch creates the support code for this function pointer
registration process.  No function pointers are included yet, but a
subsequent patch will create these for the module IDLEST registers.

This patch allows other code to use CM-provided data and operations
without needing to know which SoC is currently in use.  A further
description of the concept is provided in the patch entitled
"ARM: OMAP2+: PRM: prepare for use of prm_ll_data function pointers".
Signed-off-by: Paul Walmsley <paul@pwsan.com>

arch/arm/mach-omap2/Makefile

@@ -93,7 +93,7 @@ obj-$(CONFIG_ARCH_OMAP4)                += cpuidle44xx.o
 endif
 
 # PRCM
-obj-y					+= prcm.o prm_common.o
+obj-y					+= prcm.o prm_common.o cm_common.o
 obj-$(CONFIG_ARCH_OMAP2)		+= prm2xxx_3xxx.o prm2xxx.o cm2xxx.o
 obj-$(CONFIG_ARCH_OMAP3)		+= prm2xxx_3xxx.o prm3xxx.o cm3xxx.o
 obj-$(CONFIG_ARCH_OMAP3)		+= vc3xxx_data.o vp3xxx_data.o

arch/arm/mach-omap2/cm.h

@@ -33,4 +33,16 @@
  */
 #define MAX_MODULE_DISABLE_TIME		5000
 
+# ifndef __ASSEMBLER__
+
+/**
+ * struct cm_ll_data - fn ptrs to per-SoC CM function implementations
+ */
+struct cm_ll_data {};
+
+extern int cm_register(struct cm_ll_data *cld);
+extern int cm_unregister(struct cm_ll_data *cld);
+
+# endif
+
 #endif

arch/arm/mach-omap2/cm_common.c

+/*
+ * OMAP2+ common Clock Management (CM) IP block functions
+ *
+ * Copyright (C) 2012 Texas Instruments, Inc.
+ * Paul Walmsley <paul@pwsan.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * XXX This code should eventually be moved to a CM driver.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+
+#include "cm2xxx.h"
+#include "cm3xxx.h"
+#include "cm44xx.h"
+
+/*
+ * cm_ll_data: function pointers to SoC-specific implementations of
+ * common CM functions
+ */
+static struct cm_ll_data null_cm_ll_data;
+static struct cm_ll_data *cm_ll_data = &null_cm_ll_data;
+
+/**
+ * cm_register - register per-SoC low-level data with the CM
+ * @cld: low-level per-SoC OMAP CM data & function pointers to register
+ *
+ * Register per-SoC low-level OMAP CM data and function pointers with
+ * the OMAP CM common interface.  The caller must keep the data
+ * pointed to by @cld valid until it calls cm_unregister() and
+ * it returns successfully.  Returns 0 upon success, -EINVAL if @cld
+ * is NULL, or -EEXIST if cm_register() has already been called
+ * without an intervening cm_unregister().
+ */
+int cm_register(struct cm_ll_data *cld)
+{
+	if (!cld)
+		return -EINVAL;
+
+	if (cm_ll_data != &null_cm_ll_data)
+		return -EEXIST;
+
+	cm_ll_data = cld;
+
+	return 0;
+}
+
+/**
+ * cm_unregister - unregister per-SoC low-level data & function pointers
+ * @cld: low-level per-SoC OMAP CM data & function pointers to unregister
+ *
+ * Unregister per-SoC low-level OMAP CM data and function pointers
+ * that were previously registered with cm_register().  The
+ * caller may not destroy any of the data pointed to by @cld until
+ * this function returns successfully.  Returns 0 upon success, or
+ * -EINVAL if @cld is NULL or if @cld does not match the struct
+ * cm_ll_data * previously registered by cm_register().
+ */
+int cm_unregister(struct cm_ll_data *cld)
+{
+	if (!cld || cm_ll_data != cld)
+		return -EINVAL;
+
+	cm_ll_data = &null_cm_ll_data;
+
+	return 0;
+}