ALSA: usb-audio: Add mute TLV for playback volumes on C-Media devices

[karo-tx-linux.git] / Documentation / clk.txt

diff --git a/Documentation/clk.txt b/Documentation/clk.txt
index 22f026aa2f34202427857de1cf1554d03edd05ec..be909ed45970b24305c58e1ac2dca92c11ffbd73 100644 (file)
--- a/Documentation/clk.txt
+++ b/Documentation/clk.txt
@@ -1,12 +1,16 @@
-               The Common Clk Framework
-               Mike Turquette <mturquette@ti.com>
+========================
+The Common Clk Framework
+========================
+
+:Author: Mike Turquette <mturquette@ti.com>

 
 This document endeavours to explain the common clk framework details,
 and how to port a platform over to this framework.  It is not yet a
 detailed explanation of the clock api in include/linux/clk.h, but
 perhaps someday it will include that information.
 
 
 This document endeavours to explain the common clk framework details,
 and how to port a platform over to this framework.  It is not yet a
 detailed explanation of the clock api in include/linux/clk.h, but
 perhaps someday it will include that information.
 

-       Part 1 - introduction and interface split
+Introduction and interface split
+================================

 
 The common clk framework is an interface to control the clock nodes
 available on various devices today.  This may come in the form of clock
 
 The common clk framework is an interface to control the clock nodes
 available on various devices today.  This may come in the form of clock


@@ -35,10 +39,11 @@ is defined in struct clk_foo and pointed to within struct clk_core.  This
 allows for easy navigation between the two discrete halves of the common
 clock interface.
 
 allows for easy navigation between the two discrete halves of the common
 clock interface.
 

-       Part 2 - common data structures and api
+Common data structures and api
+==============================

 
 Below is the common struct clk_core definition from
 
 Below is the common struct clk_core definition from

-drivers/clk/clk.c, modified for brevity:
+drivers/clk/clk.c, modified for brevity::

 
        struct clk_core {
                const char              *name;
 
        struct clk_core {
                const char              *name;


@@ -59,7 +64,7 @@ struct clk.  That api is documented in include/linux/clk.h.
 
 Platforms and devices utilizing the common struct clk_core use the struct
 clk_ops pointer in struct clk_core to perform the hardware-specific parts of
 
 Platforms and devices utilizing the common struct clk_core use the struct
 clk_ops pointer in struct clk_core to perform the hardware-specific parts of

-the operations defined in clk-provider.h:
+the operations defined in clk-provider.h::

 
        struct clk_ops {
                int             (*prepare)(struct clk_hw *hw);
 
        struct clk_ops {
                int             (*prepare)(struct clk_hw *hw);


@@ -95,19 +100,20 @@ the operations defined in clk-provider.h:
                                              struct dentry *dentry);
        };
 
                                              struct dentry *dentry);
        };
 

-       Part 3 - hardware clk implementations
+Hardware clk implementations
+============================

 
 The strength of the common struct clk_core comes from its .ops and .hw pointers
 which abstract the details of struct clk from the hardware-specific bits, and
 vice versa.  To illustrate consider the simple gateable clk implementation in
 
 The strength of the common struct clk_core comes from its .ops and .hw pointers
 which abstract the details of struct clk from the hardware-specific bits, and
 vice versa.  To illustrate consider the simple gateable clk implementation in

-drivers/clk/clk-gate.c:
+drivers/clk/clk-gate.c::

 
 

-struct clk_gate {
-       struct clk_hw   hw;
-       void __iomem    *reg;
-       u8              bit_idx;
-       ...
-};
+       struct clk_gate {
+               struct clk_hw   hw;
+               void __iomem    *reg;
+               u8              bit_idx;
+               ...
+       };

 
 struct clk_gate contains struct clk_hw hw as well as hardware-specific
 knowledge about which register and bit controls this clk's gating.
 
 struct clk_gate contains struct clk_hw hw as well as hardware-specific
 knowledge about which register and bit controls this clk's gating.


@@ -115,7 +121,7 @@ Nothing about clock topology or accounting, such as enable_count or
 notifier_count, is needed here.  That is all handled by the common
 framework code and struct clk_core.
 
 notifier_count, is needed here.  That is all handled by the common
 framework code and struct clk_core.
 

-Let's walk through enabling this clk from driver code:
+Let's walk through enabling this clk from driver code::

 
        struct clk *clk;
        clk = clk_get(NULL, "my_gateable_clk");
 
        struct clk *clk;
        clk = clk_get(NULL, "my_gateable_clk");


@@ -123,70 +129,71 @@ Let's walk through enabling this clk from driver code:
        clk_prepare(clk);
        clk_enable(clk);
 
        clk_prepare(clk);
        clk_enable(clk);
 

-The call graph for clk_enable is very simple:
+The call graph for clk_enable is very simple::

 
 

-clk_enable(clk);
-       clk->ops->enable(clk->hw);
-       [resolves to...]
-               clk_gate_enable(hw);
-               [resolves struct clk gate with to_clk_gate(hw)]
-                       clk_gate_set_bit(gate);
+       clk_enable(clk);
+               clk->ops->enable(clk->hw);
+               [resolves to...]
+                       clk_gate_enable(hw);
+                       [resolves struct clk gate with to_clk_gate(hw)]
+                               clk_gate_set_bit(gate);

 
 

-And the definition of clk_gate_set_bit:
+And the definition of clk_gate_set_bit::

 
 

-static void clk_gate_set_bit(struct clk_gate *gate)
-{
-       u32 reg;
+       static void clk_gate_set_bit(struct clk_gate *gate)
+       {
+               u32 reg;

 
 

-       reg = __raw_readl(gate->reg);
-       reg |= BIT(gate->bit_idx);
-       writel(reg, gate->reg);
-}
+               reg = __raw_readl(gate->reg);
+               reg |= BIT(gate->bit_idx);
+               writel(reg, gate->reg);
+       }

 
 

-Note that to_clk_gate is defined as:
+Note that to_clk_gate is defined as::

 
 

-#define to_clk_gate(_hw) container_of(_hw, struct clk_gate, hw)
+       #define to_clk_gate(_hw) container_of(_hw, struct clk_gate, hw)

 
 This pattern of abstraction is used for every clock hardware
 representation.
 
 
 This pattern of abstraction is used for every clock hardware
 representation.
 

-       Part 4 - supporting your own clk hardware
+Supporting your own clk hardware
+================================

 
 When implementing support for a new type of clock it is only necessary to
 
 When implementing support for a new type of clock it is only necessary to

-include the following header:
+include the following header::

 
 

-#include <linux/clk-provider.h>
+       #include <linux/clk-provider.h>

 
 To construct a clk hardware structure for your platform you must define
 
 To construct a clk hardware structure for your platform you must define

-the following:
+the following::

 
 

-struct clk_foo {
-       struct clk_hw hw;
-       ... hardware specific data goes here ...
-};
+       struct clk_foo {
+               struct clk_hw hw;
+               ... hardware specific data goes here ...
+       };

 
 To take advantage of your data you'll need to support valid operations
 
 To take advantage of your data you'll need to support valid operations

-for your clk:
+for your clk::

 
 

-struct clk_ops clk_foo_ops {
-       .enable         = &clk_foo_enable;
-       .disable        = &clk_foo_disable;
-};
+       struct clk_ops clk_foo_ops {
+               .enable         = &clk_foo_enable;
+               .disable        = &clk_foo_disable;
+       };

 
 

-Implement the above functions using container_of:
+Implement the above functions using container_of::

 
 

-#define to_clk_foo(_hw) container_of(_hw, struct clk_foo, hw)
+       #define to_clk_foo(_hw) container_of(_hw, struct clk_foo, hw)

 
 

-int clk_foo_enable(struct clk_hw *hw)
-{
-       struct clk_foo *foo;
+       int clk_foo_enable(struct clk_hw *hw)
+       {
+               struct clk_foo *foo;

 
 

-       foo = to_clk_foo(hw);
+               foo = to_clk_foo(hw);

 
 

-       ... perform magic on foo ...
+               ... perform magic on foo ...

 
 

-       return 0;
-};
+               return 0;
+       };

 
 Below is a matrix detailing which clk_ops are mandatory based upon the
 hardware capabilities of that clock.  A cell marked as "y" means
 
 Below is a matrix detailing which clk_ops are mandatory based upon the
 hardware capabilities of that clock.  A cell marked as "y" means


@@ -194,41 +201,56 @@ mandatory, a cell marked as "n" implies that either including that
 callback is invalid or otherwise unnecessary.  Empty cells are either
 optional or must be evaluated on a case-by-case basis.
 
 callback is invalid or otherwise unnecessary.  Empty cells are either
 optional or must be evaluated on a case-by-case basis.
 

-                              clock hardware characteristics
-                -----------------------------------------------------------
-                | gate | change rate | single parent | multiplexer | root |
-                |------|-------------|---------------|-------------|------|
-.prepare        |      |             |               |             |      |
-.unprepare      |      |             |               |             |      |
-                |      |             |               |             |      |
-.enable         | y    |             |               |             |      |
-.disable        | y    |             |               |             |      |
-.is_enabled     | y    |             |               |             |      |
-                |      |             |               |             |      |
-.recalc_rate    |      | y           |               |             |      |
-.round_rate     |      | y [1]       |               |             |      |
-.determine_rate |      | y [1]       |               |             |      |
-.set_rate       |      | y           |               |             |      |
-                |      |             |               |             |      |
-.set_parent     |      |             | n             | y           | n    |
-.get_parent     |      |             | n             | y           | n    |
-                |      |             |               |             |      |
-.recalc_accuracy|      |             |               |             |      |
-                |      |             |               |             |      |
-.init           |      |             |               |             |      |
-                -----------------------------------------------------------
-[1] either one of round_rate or determine_rate is required.
+.. table:: clock hardware characteristics
+
+   +----------------+------+-------------+---------------+-------------+------+
+   |                | gate | change rate | single parent | multiplexer | root |
+   +================+======+=============+===============+=============+======+
+   |.prepare        |      |             |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   |.unprepare      |      |             |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   +----------------+------+-------------+---------------+-------------+------+
+   |.enable         | y    |             |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   |.disable        | y    |             |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   |.is_enabled     | y    |             |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   +----------------+------+-------------+---------------+-------------+------+
+   |.recalc_rate    |      | y           |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   |.round_rate     |      | y [1]_      |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   |.determine_rate |      | y [1]_      |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   |.set_rate       |      | y           |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   +----------------+------+-------------+---------------+-------------+------+
+   |.set_parent     |      |             | n             | y           | n    |
+   +----------------+------+-------------+---------------+-------------+------+
+   |.get_parent     |      |             | n             | y           | n    |
+   +----------------+------+-------------+---------------+-------------+------+
+   +----------------+------+-------------+---------------+-------------+------+
+   |.recalc_accuracy|      |             |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+   +----------------+------+-------------+---------------+-------------+------+
+   |.init           |      |             |               |             |      |
+   +----------------+------+-------------+---------------+-------------+------+
+
+.. [1] either one of round_rate or determine_rate is required.

 
 Finally, register your clock at run-time with a hardware-specific
 registration function.  This function simply populates struct clk_foo's
 data and then passes the common struct clk parameters to the framework
 
 Finally, register your clock at run-time with a hardware-specific
 registration function.  This function simply populates struct clk_foo's
 data and then passes the common struct clk parameters to the framework

-with a call to:
+with a call to::

 
 

-clk_register(...)
+       clk_register(...)

 
 

-See the basic clock types in drivers/clk/clk-*.c for examples.
+See the basic clock types in ``drivers/clk/clk-*.c`` for examples.

 
 

-       Part 5 - Disabling clock gating of unused clocks
+Disabling clock gating of unused clocks
+=======================================

 
 Sometimes during development it can be useful to be able to bypass the
 default disabling of unused clocks. For example, if drivers aren't enabling
 
 Sometimes during development it can be useful to be able to bypass the
 default disabling of unused clocks. For example, if drivers aren't enabling


@@ -239,7 +261,8 @@ are sorted out.
 To bypass this disabling, include "clk_ignore_unused" in the bootargs to the
 kernel.
 
 To bypass this disabling, include "clk_ignore_unused" in the bootargs to the
 kernel.
 

-       Part 6 - Locking
+Locking
+=======

 
 The common clock framework uses two global locks, the prepare lock and the
 enable lock.
 
 The common clock framework uses two global locks, the prepare lock and the
 enable lock.