clk: bcm281xx: add initial clock framework support

Add code for device tree support of clocks in the BCM281xx family of
SoCs.  Machines in this family use peripheral clocks implemented by
"Kona" clock control units (CCUs).  (Other Broadcom SoC families use
Kona style CCUs as well, but support for them is not yet upstream.)

A BCM281xx SoC has multiple CCUs, each of which manages a set of
clocks on the SoC.  A Kona peripheral clock is composite clock that
may include a gate, a parent clock multiplexor, and zero, one
or two dividers.  There is a variety of gate types, and many gates
implement hardware-managed gating (often called "auto-gating").
Most dividers divide their input clock signal by an integer value
(one or more).  There are also "fractional" dividers which allow
division by non-integer values.  To accomodate such dividers,
clock rates and dividers are generally maintained by the code in
"scaled" form, which allows integer and fractional dividers to
be handled in a uniform way.

If present, the gate for a Kona peripheral clock must be enabled
when a change is made to its multiplexor or one of its dividers.
Additionally, dividers and multiplexors have trigger registers which
must be used whenever the divider value or selected parent clock is
changed.  The same trigger is often used for a divider and
multiplexor, and a BCM281xx peripheral clock occasionally has two
triggers.

The gate, dividers, and parent clock selector are treated in this
code as "components" of a peripheral clock.  Their functionality is
implemented directly--e.g. the common clock framework gate
implementation is not used for a Kona peripheral clock gate.  (This
has being considered though, and the intention is to evolve this
code to leverage common code as much as possible.)

The source code is divided into three general portions:

    drivers/clk/bcm/clk-kona.h
    drivers/clk/bcm/clk-kona.c
        These implement the basic Kona clock functionality,
        including the clk_ops methods and various routines to
        manipulate registers and interpret their values.  This
        includes some functions used to set clocks to a desired
        initial state (though this feature is only partially
        implemented here).

    drivers/clk/bcm/clk-kona-setup.c
        This contains generic run-time initialization code for
        data structures representing Kona CCUs and clocks.  This
        encapsulates the clock structure initialization that can't
        be done statically.  Note that there is a great deal of
        validity-checking code here, making explicit certain
        assumptions in the code.   This is mostly useful for adding
        new clock definitions and could possibly be disabled for
        production use.

    drivers/clk/bcm/clk-bcm281xx.c
        This file defines the specific CCUs used by BCM281XX family
        SoCs, as well as the specific clocks implemented by each.
        It declares a device tree clock match entry for each CCU
        defined.

    include/dt-bindings/clock/bcm281xx.h
        This file defines the selector (index) values used to
        identify a particular clock provided by a CCU.  It consists
        entirely of C preprocessor constants, to be used by both the
        C source and device tree source files.

Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Tim Kryger <tim.kryger@linaro.org>
Reviewed-by: Matt Porter <mporter@linaro.org>
Acked-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Matt Porter <mporter@linaro.org>

1 files changed, 410 insertions, 0 deletions

diff --git a/drivers/clk/bcm/clk-kona.h b/drivers/clk/bcm/clk-kona.h
new file mode 100644
index 000000000000..5e139adc3dc5
--- /dev/null
+++ b/drivers/clk/bcm/clk-kona.h
@@ -0,0 +1,410 @@
+/*
+ * Copyright (C) 2013 Broadcom Corporation
+ * Copyright 2013 Linaro Limited
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation version 2.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef _CLK_KONA_H
+#define _CLK_KONA_H
+
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+#include <linux/of.h>
+#include <linux/clk-provider.h>
+
+#define	BILLION		1000000000
+
+/* The common clock framework uses u8 to represent a parent index */
+#define PARENT_COUNT_MAX	((u32)U8_MAX)
+
+#define BAD_CLK_INDEX		U8_MAX	/* Can't ever be valid */
+#define BAD_CLK_NAME		((const char *)-1)
+
+#define BAD_SCALED_DIV_VALUE	U64_MAX
+
+/*
+ * Utility macros for object flag management.  If possible, flags
+ * should be defined such that 0 is the desired default value.
+ */
+#define FLAG(type, flag)		BCM_CLK_ ## type ## _FLAGS_ ## flag
+#define FLAG_SET(obj, type, flag)	((obj)->flags |= FLAG(type, flag))
+#define FLAG_CLEAR(obj, type, flag)	((obj)->flags &= ~(FLAG(type, flag)))
+#define FLAG_FLIP(obj, type, flag)	((obj)->flags ^= FLAG(type, flag))
+#define FLAG_TEST(obj, type, flag)	(!!((obj)->flags & FLAG(type, flag)))
+
+/* Clock field state tests */
+
+#define gate_exists(gate)		FLAG_TEST(gate, GATE, EXISTS)
+#define gate_is_enabled(gate)		FLAG_TEST(gate, GATE, ENABLED)
+#define gate_is_hw_controllable(gate)	FLAG_TEST(gate, GATE, HW)
+#define gate_is_sw_controllable(gate)	FLAG_TEST(gate, GATE, SW)
+#define gate_is_sw_managed(gate)	FLAG_TEST(gate, GATE, SW_MANAGED)
+#define gate_is_no_disable(gate)	FLAG_TEST(gate, GATE, NO_DISABLE)
+
+#define gate_flip_enabled(gate)		FLAG_FLIP(gate, GATE, ENABLED)
+
+#define divider_exists(div)		FLAG_TEST(div, DIV, EXISTS)
+#define divider_is_fixed(div)		FLAG_TEST(div, DIV, FIXED)
+#define divider_has_fraction(div)	(!divider_is_fixed(div) && \
+						(div)->frac_width > 0)
+
+#define selector_exists(sel)		((sel)->width != 0)
+#define trigger_exists(trig)		FLAG_TEST(trig, TRIG, EXISTS)
+
+/* Clock type, used to tell common block what it's part of */
+enum bcm_clk_type {
+	bcm_clk_none,		/* undefined clock type */
+	bcm_clk_bus,
+	bcm_clk_core,
+	bcm_clk_peri
+};
+
+/*
+ * Each CCU defines a mapped area of memory containing registers
+ * used to manage clocks implemented by the CCU.  Access to memory
+ * within the CCU's space is serialized by a spinlock.  Before any
+ * (other) address can be written, a special access "password" value
+ * must be written to its WR_ACCESS register (located at the base
+ * address of the range).  We keep track of the name of each CCU as
+ * it is set up, and maintain them in a list.
+ */
+struct ccu_data {
+	void __iomem *base;	/* base of mapped address space */
+	spinlock_t lock;	/* serialization lock */
+	bool write_enabled;	/* write access is currently enabled */
+	struct list_head links;	/* for ccu_list */
+	struct device_node *node;
+	struct clk_onecell_data data;
+	const char *name;
+	u32 range;		/* byte range of address space */
+};
+
+/*
+ * Gating control and status is managed by a 32-bit gate register.
+ *
+ * There are several types of gating available:
+ * - (no gate)
+ *     A clock with no gate is assumed to be always enabled.
+ * - hardware-only gating (auto-gating)
+ *     Enabling or disabling clocks with this type of gate is
+ *     managed automatically by the hardware.  Such clocks can be
+ *     considered by the software to be enabled.  The current status
+ *     of auto-gated clocks can be read from the gate status bit.
+ * - software-only gating
+ *     Auto-gating is not available for this type of clock.
+ *     Instead, software manages whether it's enabled by setting or
+ *     clearing the enable bit.  The current gate status of a gate
+ *     under software control can be read from the gate status bit.
+ *     To ensure a change to the gating status is complete, the
+ *     status bit can be polled to verify that the gate has entered
+ *     the desired state.
+ * - selectable hardware or software gating
+ *     Gating for this type of clock can be configured to be either
+ *     under software or hardware control.  Which type is in use is
+ *     determined by the hw_sw_sel bit of the gate register.
+ */
+struct bcm_clk_gate {
+	u32 offset;		/* gate register offset */
+	u32 status_bit;		/* 0: gate is disabled; 0: gatge is enabled */
+	u32 en_bit;		/* 0: disable; 1: enable */
+	u32 hw_sw_sel_bit;	/* 0: hardware gating; 1: software gating */
+	u32 flags;		/* BCM_CLK_GATE_FLAGS_* below */
+};
+
+/*
+ * Gate flags:
+ *   HW         means this gate can be auto-gated
+ *   SW         means the state of this gate can be software controlled
+ *   NO_DISABLE means this gate is (only) enabled if under software control
+ *   SW_MANAGED means the status of this gate is under software control
+ *   ENABLED    means this software-managed gate is *supposed* to be enabled
+ */
+#define BCM_CLK_GATE_FLAGS_EXISTS	((u32)1 << 0)	/* Gate is valid */
+#define BCM_CLK_GATE_FLAGS_HW		((u32)1 << 1)	/* Can auto-gate */
+#define BCM_CLK_GATE_FLAGS_SW		((u32)1 << 2)	/* Software control */
+#define BCM_CLK_GATE_FLAGS_NO_DISABLE	((u32)1 << 3)	/* HW or enabled */
+#define BCM_CLK_GATE_FLAGS_SW_MANAGED	((u32)1 << 4)	/* SW now in control */
+#define BCM_CLK_GATE_FLAGS_ENABLED	((u32)1 << 5)	/* If SW_MANAGED */
+
+/*
+ * Gate initialization macros.
+ *
+ * Any gate initially under software control will be enabled.
+ */
+
+/* A hardware/software gate initially under software control */
+#define HW_SW_GATE(_offset, _status_bit, _en_bit, _hw_sw_sel_bit)	\
+	{								\
+		.offset = (_offset),					\
+		.status_bit = (_status_bit),				\
+		.en_bit = (_en_bit),					\
+		.hw_sw_sel_bit = (_hw_sw_sel_bit),			\
+		.flags = FLAG(GATE, HW)|FLAG(GATE, SW)|			\
+			FLAG(GATE, SW_MANAGED)|FLAG(GATE, ENABLED)|	\
+			FLAG(GATE, EXISTS),				\
+	}
+
+/* A hardware/software gate initially under hardware control */
+#define HW_SW_GATE_AUTO(_offset, _status_bit, _en_bit, _hw_sw_sel_bit)	\
+	{								\
+		.offset = (_offset),					\
+		.status_bit = (_status_bit),				\
+		.en_bit = (_en_bit),					\
+		.hw_sw_sel_bit = (_hw_sw_sel_bit),			\
+		.flags = FLAG(GATE, HW)|FLAG(GATE, SW)|			\
+			FLAG(GATE, EXISTS),				\
+	}
+
+/* A hardware-or-enabled gate (enabled if not under hardware control) */
+#define HW_ENABLE_GATE(_offset, _status_bit, _en_bit, _hw_sw_sel_bit)	\
+	{								\
+		.offset = (_offset),					\
+		.status_bit = (_status_bit),				\
+		.en_bit = (_en_bit),					\
+		.hw_sw_sel_bit = (_hw_sw_sel_bit),			\
+		.flags = FLAG(GATE, HW)|FLAG(GATE, SW)|			\
+			FLAG(GATE, NO_DISABLE)|FLAG(GATE, EXISTS),	\
+	}
+
+/* A software-only gate */
+#define SW_ONLY_GATE(_offset, _status_bit, _en_bit)			\
+	{								\
+		.offset = (_offset),					\
+		.status_bit = (_status_bit),				\
+		.en_bit = (_en_bit),					\
+		.flags = FLAG(GATE, SW)|FLAG(GATE, SW_MANAGED)|		\
+			FLAG(GATE, ENABLED)|FLAG(GATE, EXISTS),		\
+	}
+
+/* A hardware-only gate */
+#define HW_ONLY_GATE(_offset, _status_bit)				\
+	{								\
+		.offset = (_offset),					\
+		.status_bit = (_status_bit),				\
+		.flags = FLAG(GATE, HW)|FLAG(GATE, EXISTS),		\
+	}
+
+/*
+ * Each clock can have zero, one, or two dividers which change the
+ * output rate of the clock.  Each divider can be either fixed or
+ * variable.  If there are two dividers, they are the "pre-divider"
+ * and the "regular" or "downstream" divider.  If there is only one,
+ * there is no pre-divider.
+ *
+ * A fixed divider is any non-zero (positive) value, and it
+ * indicates how the input rate is affected by the divider.
+ *
+ * The value of a variable divider is maintained in a sub-field of a
+ * 32-bit divider register.  The position of the field in the
+ * register is defined by its offset and width.  The value recorded
+ * in this field is always 1 less than the value it represents.
+ *
+ * In addition, a variable divider can indicate that some subset
+ * of its bits represent a "fractional" part of the divider.  Such
+ * bits comprise the low-order portion of the divider field, and can
+ * be viewed as representing the portion of the divider that lies to
+ * the right of the decimal point.  Most variable dividers have zero
+ * fractional bits.  Variable dividers with non-zero fraction width
+ * still record a value 1 less than the value they represent; the
+ * added 1 does *not* affect the low-order bit in this case, it
+ * affects the bits above the fractional part only.  (Often in this
+ * code a divider field value is distinguished from the value it
+ * represents by referring to the latter as a "divisor".)
+ *
+ * In order to avoid dealing with fractions, divider arithmetic is
+ * performed using "scaled" values.  A scaled value is one that's
+ * been left-shifted by the fractional width of a divider.  Dividing
+ * a scaled value by a scaled divisor produces the desired quotient
+ * without loss of precision and without any other special handling
+ * for fractions.
+ *
+ * The recorded value of a variable divider can be modified.  To
+ * modify either divider (or both), a clock must be enabled (i.e.,
+ * using its gate).  In addition, a trigger register (described
+ * below) must be used to commit the change, and polled to verify
+ * the change is complete.
+ */
+struct bcm_clk_div {
+	union {
+		struct {	/* variable divider */
+			u32 offset;	/* divider register offset */
+			u32 shift;	/* field shift */
+			u32 width;	/* field width */
+			u32 frac_width;	/* field fraction width */
+
+			u64 scaled_div;	/* scaled divider value */
+		};
+		u32 fixed;	/* non-zero fixed divider value */
+	};
+	u32 flags;		/* BCM_CLK_DIV_FLAGS_* below */
+};
+
+/*
+ * Divider flags:
+ *   EXISTS means this divider exists
+ *   FIXED means it is a fixed-rate divider
+ */
+#define BCM_CLK_DIV_FLAGS_EXISTS	((u32)1 << 0)	/* Divider is valid */
+#define BCM_CLK_DIV_FLAGS_FIXED		((u32)1 << 1)	/* Fixed-value */
+
+/* Divider initialization macros */
+
+/* A fixed (non-zero) divider */
+#define FIXED_DIVIDER(_value)						\
+	{								\
+		.fixed = (_value),					\
+		.flags = FLAG(DIV, EXISTS)|FLAG(DIV, FIXED),		\
+	}
+
+/* A divider with an integral divisor */
+#define DIVIDER(_offset, _shift, _width)				\
+	{								\
+		.offset = (_offset),					\
+		.shift = (_shift),					\
+		.width = (_width),					\
+		.scaled_div = BAD_SCALED_DIV_VALUE,			\
+		.flags = FLAG(DIV, EXISTS),				\
+	}
+
+/* A divider whose divisor has an integer and fractional part */
+#define FRAC_DIVIDER(_offset, _shift, _width, _frac_width)		\
+	{								\
+		.offset = (_offset),					\
+		.shift = (_shift),					\
+		.width = (_width),					\
+		.frac_width = (_frac_width),				\
+		.scaled_div = BAD_SCALED_DIV_VALUE,			\
+		.flags = FLAG(DIV, EXISTS),				\
+	}
+
+/*
+ * Clocks may have multiple "parent" clocks.  If there is more than
+ * one, a selector must be specified to define which of the parent
+ * clocks is currently in use.  The selected clock is indicated in a
+ * sub-field of a 32-bit selector register.  The range of
+ * representable selector values typically exceeds the number of
+ * available parent clocks.  Occasionally the reset value of a
+ * selector field is explicitly set to a (specific) value that does
+ * not correspond to a defined input clock.
+ *
+ * We register all known parent clocks with the common clock code
+ * using a packed array (i.e., no empty slots) of (parent) clock
+ * names, and refer to them later using indexes into that array.
+ * We maintain an array of selector values indexed by common clock
+ * index values in order to map between these common clock indexes
+ * and the selector values used by the hardware.
+ *
+ * Like dividers, a selector can be modified, but to do so a clock
+ * must be enabled, and a trigger must be used to commit the change.
+ */
+struct bcm_clk_sel {
+	u32 offset;		/* selector register offset */
+	u32 shift;		/* field shift */
+	u32 width;		/* field width */
+
+	u32 parent_count;	/* number of entries in parent_sel[] */
+	u32 *parent_sel;	/* array of parent selector values */
+	u8 clk_index;		/* current selected index in parent_sel[] */
+};
+
+/* Selector initialization macro */
+#define SELECTOR(_offset, _shift, _width)				\
+	{								\
+		.offset = (_offset),					\
+		.shift = (_shift),					\
+		.width = (_width),					\
+		.clk_index = BAD_CLK_INDEX,				\
+	}
+
+/*
+ * Making changes to a variable divider or a selector for a clock
+ * requires the use of a trigger.  A trigger is defined by a single
+ * bit within a register.  To signal a change, a 1 is written into
+ * that bit.  To determine when the change has been completed, that
+ * trigger bit is polled; the read value will be 1 while the change
+ * is in progress, and 0 when it is complete.
+ *
+ * Occasionally a clock will have more than one trigger.  In this
+ * case, the "pre-trigger" will be used when changing a clock's
+ * selector and/or its pre-divider.
+ */
+struct bcm_clk_trig {
+	u32 offset;		/* trigger register offset */
+	u32 bit;		/* trigger bit */
+	u32 flags;		/* BCM_CLK_TRIG_FLAGS_* below */
+};
+
+/*
+ * Trigger flags:
+ *   EXISTS means this trigger exists
+ */
+#define BCM_CLK_TRIG_FLAGS_EXISTS	((u32)1 << 0)	/* Trigger is valid */
+
+/* Trigger initialization macro */
+#define TRIGGER(_offset, _bit)						\
+	{								\
+		.offset = (_offset),					\
+		.bit = (_bit),						\
+		.flags = FLAG(TRIG, EXISTS),				\
+	}
+
+struct peri_clk_data {
+	struct bcm_clk_gate gate;
+	struct bcm_clk_trig pre_trig;
+	struct bcm_clk_div pre_div;
+	struct bcm_clk_trig trig;
+	struct bcm_clk_div div;
+	struct bcm_clk_sel sel;
+	const char *clocks[];	/* must be last; use CLOCKS() to declare */
+};
+#define CLOCKS(...)	{ __VA_ARGS__, NULL, }
+#define NO_CLOCKS	{ NULL, }	/* Must use of no parent clocks */
+
+struct kona_clk {
+	struct clk_hw hw;
+	struct clk_init_data init_data;
+	const char *name;	/* name of this clock */
+	struct ccu_data *ccu;	/* ccu this clock is associated with */
+	enum bcm_clk_type type;
+	union {
+		void *data;
+		struct peri_clk_data *peri;
+	};
+};
+#define to_kona_clk(_hw) \
+	container_of(_hw, struct kona_clk, hw)
+
+/* Exported globals */
+
+extern struct clk_ops kona_peri_clk_ops;
+
+/* Help functions */
+
+#define PERI_CLK_SETUP(clks, ccu, id, name) \
+	clks[id] = kona_clk_setup(ccu, #name, bcm_clk_peri, &name ## _data)
+
+/* Externally visible functions */
+
+extern u64 do_div_round_closest(u64 dividend, unsigned long divisor);
+extern u64 scaled_div_max(struct bcm_clk_div *div);
+extern u64 scaled_div_build(struct bcm_clk_div *div, u32 div_value,
+				u32 billionths);
+
+extern struct clk *kona_clk_setup(struct ccu_data *ccu, const char *name,
+			enum bcm_clk_type type, void *data);
+extern void __init kona_dt_ccu_setup(struct device_node *node,
+			int (*ccu_clks_setup)(struct ccu_data *));
+extern bool __init kona_ccu_init(struct ccu_data *ccu);
+
+#endif /* _CLK_KONA_H */