include/clk.h

   1 /*
   2  * Copyright (c) 2015 Google, Inc
   3  * Written by Simon Glass <sjg@chromium.org>
   4  * Copyright (c) 2016, NVIDIA CORPORATION.
   5  *
   6  * SPDX-License-Identifier:     GPL-2.0+
   7  */
   8
   9 #ifndef _CLK_H_
  10 #define _CLK_H_
  11
  12 #include <linux/types.h>
  13
  14 /**
  15  * A clock is a hardware signal that oscillates autonomously at a specific
  16  * frequency and duty cycle. Most hardware modules require one or more clock
  17  * signal to drive their operation. Clock signals are typically generated
  18  * externally to the HW module consuming them, by an entity this API calls a
  19  * clock provider. This API provides a standard means for drivers to enable and
  20  * disable clocks, and to set the rate at which they oscillate.
  21  *
  22  * A driver that implements UCLASS_CLOCK is a clock provider. A provider will
  23  * often implement multiple separate clocks, since the hardware it manages
  24  * often has this capability. clock_uclass.h describes the interface which
  25  * clock providers must implement.
  26  *
  27  * Clock consumers/clients are the HW modules driven by the clock signals. This
  28  * header file describes the API used by drivers for those HW modules.
  29  */
  30
  31 struct udevice;
  32
  33 /**
  34  * struct clk - A handle to (allowing control of) a single clock.
  35  *
  36  * Clients provide storage for clock handles. The content of the structure is
  37  * managed solely by the clock API and clock drivers. A clock struct is
  38  * initialized by "get"ing the clock struct. The clock struct is passed to all
  39  * other clock APIs to identify which clock signal to operate upon.
  40  *
  41  * @dev: The device which implements the clock signal.
  42  * @id: The clock signal ID within the provider.
  43  *
  44  * Currently, the clock API assumes that a single integer ID is enough to
  45  * identify and configure any clock signal for any clock provider. If this
  46  * assumption becomes invalid in the future, the struct could be expanded to
  47  * either (a) add more fields to allow clock providers to store additional
  48  * information, or (b) replace the id field with an opaque pointer, which the
  49  * provider would dynamically allocated during its .of_xlate op, and process
  50  * during is .request op. This may require the addition of an extra op to clean
  51  * up the allocation.
  52  */
  53 struct clk {
  54         struct udevice *dev;
  55         /*
  56          * Written by of_xlate. We assume a single id is enough for now. In the
  57          * future, we might add more fields here.
  58          */
  59         unsigned long id;
  60 };
  61
  62 #if CONFIG_IS_ENABLED(OF_CONTROL)
  63 /**
  64  * clock_get_by_index - Get/request a clock by integer index.
  65  *
  66  * This looks up and requests a clock. The index is relative to the client
  67  * device; each device is assumed to have n clocks associated with it somehow,
  68  * and this function finds and requests one of them. The mapping of client
  69  * device clock indices to provider clocks may be via device-tree properties,
  70  * board-provided mapping tables, or some other mechanism.
  71  *
  72  * @dev:        The client device.
  73  * @index:      The index of the clock to request, within the client's list of
  74  *              clocks.
  75  * @clock       A pointer to a clock struct to initialize.
  76  * @return 0 if OK, or a negative error code.
  77  */
  78 int clk_get_by_index(struct udevice *dev, int index, struct clk *clk);
  79
  80 /**
  81  * clock_get_by_name - Get/request a clock by name.
  82  *
  83  * This looks up and requests a clock. The name is relative to the client
  84  * device; each device is assumed to have n clocks associated with it somehow,
  85  * and this function finds and requests one of them. The mapping of client
  86  * device clock names to provider clocks may be via device-tree properties,
  87  * board-provided mapping tables, or some other mechanism.
  88  *
  89  * @dev:        The client device.
  90  * @name:       The name of the clock to request, within the client's list of
  91  *              clocks.
  92  * @clock:      A pointer to a clock struct to initialize.
  93  * @return 0 if OK, or a negative error code.
  94  */
  95 int clk_get_by_name(struct udevice *dev, const char *name, struct clk *clk);
  96 #else
  97 static inline int clk_get_by_index(struct udevice *dev, int index,
  98                                    struct clk *clk)
  99 {
 100         return -ENOSYS;
 101 }
 102
 103 static int clk_get_by_name(struct udevice *dev, const char *name,
 104                            struct clk *clk)
 105 {
 106         return -ENOSYS;
 107 }
 108 #endif
 109
 110 /**
 111  * clk_request - Request a clock by provider-specific ID.
 112  *
 113  * This requests a clock using a provider-specific ID. Generally, this function
 114  * should not be used, since clk_get_by_index/name() provide an interface that
 115  * better separates clients from intimate knowledge of clock providers.
 116  * However, this function may be useful in core SoC-specific code.
 117  *
 118  * @dev:        The clock provider device.
 119  * @clock:      A pointer to a clock struct to initialize. The caller must
 120  *              have already initialized any field in this struct which the
 121  *              clock provider uses to identify the clock.
 122  * @return 0 if OK, or a negative error code.
 123  */
 124 int clk_request(struct udevice *dev, struct clk *clk);
 125
 126 /**
 127  * clock_free - Free a previously requested clock.
 128  *
 129  * @clock:      A clock struct that was previously successfully requested by
 130  *              clk_request/get_by_*().
 131  * @return 0 if OK, or a negative error code.
 132  */
 133 int clk_free(struct clk *clk);
 134
 135 /**
 136  * clk_get_rate() - Get current clock rate.
 137  *
 138  * @clk:        A clock struct that was previously successfully requested by
 139  *              clk_request/get_by_*().
 140  * @return clock rate in Hz, or -ve error code.
 141  */
 142 ulong clk_get_rate(struct clk *clk);
 143
 144 /**
 145  * clk_set_rate() - Set current clock rate.
 146  *
 147  * @clk:        A clock struct that was previously successfully requested by
 148  *              clk_request/get_by_*().
 149  * @rate:       New clock rate in Hz.
 150  * @return new rate, or -ve error code.
 151  */
 152 ulong clk_set_rate(struct clk *clk, ulong rate);
 153
 154 /**
 155  * clk_enable() - Enable (turn on) a clock.
 156  *
 157  * @clk:        A clock struct that was previously successfully requested by
 158  *              clk_request/get_by_*().
 159  * @return zero on success, or -ve error code.
 160  */
 161 int clk_enable(struct clk *clk);
 162
 163 /**
 164  * clk_disable() - Disable (turn off) a clock.
 165  *
 166  * @clk:        A clock struct that was previously successfully requested by
 167  *              clk_request/get_by_*().
 168  * @return zero on success, or -ve error code.
 169  */
 170 int clk_disable(struct clk *clk);
 171
 172 int soc_clk_dump(void);
 173
 174 #endif