Re: [U-Boot] [PATCH V2 3/5] Add a reset driver framework/uclass

[Simon Glass]

On 17 June 2016 at 09:43, Stephen Warren  wrote:
> From: Stephen Warren 
>
> A reset controller is a hardware module that controls reset signals that
> affect other hardware modules or chips.
>
> This patch defines a standard API that connects reset clients (i.e. the
> drivers for devices affected by reset signals) to drivers for reset
> controllers/providers. Initially, DT is the only supported method for
> connecting the two.
>
> The DT binding specification (reset.txt) was taken from Linux kernel
> v4.5's Documentation/devicetree/bindings/reset/reset.txt.
>
> Signed-off-by: Stephen Warren 
> Acked-by: Simon Glass 
> ---
> v2: Renamed header files.
> ---
>  doc/device-tree-bindings/reset/reset.txt |  75 +
>  drivers/Kconfig  |   2 +
>  drivers/Makefile |   1 +
>  drivers/reset/Kconfig|  15 
>  drivers/reset/Makefile   |   5 ++
>  drivers/reset/reset-uclass.c | 131 ++
>  include/dm/uclass-id.h   |   1 +
>  include/reset-uclass.h   |  81 +++
>  include/reset.h  | 135 
> +++
>  9 files changed, 446 insertions(+)
>  create mode 100644 doc/device-tree-bindings/reset/reset.txt
>  create mode 100644 drivers/reset/Kconfig
>  create mode 100644 drivers/reset/Makefile
>  create mode 100644 drivers/reset/reset-uclass.c
>  create mode 100644 include/reset-uclass.h
>  create mode 100644 include/reset.h

Applied to u-boot-dm, thanks!
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[U-Boot] [PATCH V2 3/5] Add a reset driver framework/uclass

[Stephen Warren]

From: Stephen Warren 

A reset controller is a hardware module that controls reset signals that
affect other hardware modules or chips.

This patch defines a standard API that connects reset clients (i.e. the
drivers for devices affected by reset signals) to drivers for reset
controllers/providers. Initially, DT is the only supported method for
connecting the two.

The DT binding specification (reset.txt) was taken from Linux kernel
v4.5's Documentation/devicetree/bindings/reset/reset.txt.

Signed-off-by: Stephen Warren 
Acked-by: Simon Glass 
---
v2: Renamed header files.
---
 doc/device-tree-bindings/reset/reset.txt |  75 +
 drivers/Kconfig  |   2 +
 drivers/Makefile |   1 +
 drivers/reset/Kconfig|  15 
 drivers/reset/Makefile   |   5 ++
 drivers/reset/reset-uclass.c | 131 ++
 include/dm/uclass-id.h   |   1 +
 include/reset-uclass.h   |  81 +++
 include/reset.h  | 135 +++
 9 files changed, 446 insertions(+)
 create mode 100644 doc/device-tree-bindings/reset/reset.txt
 create mode 100644 drivers/reset/Kconfig
 create mode 100644 drivers/reset/Makefile
 create mode 100644 drivers/reset/reset-uclass.c
 create mode 100644 include/reset-uclass.h
 create mode 100644 include/reset.h

diff --git a/doc/device-tree-bindings/reset/reset.txt 
b/doc/device-tree-bindings/reset/reset.txt
new file mode 100644
index ..31db6ff84908
--- /dev/null
+++ b/doc/device-tree-bindings/reset/reset.txt
@@ -0,0 +1,75 @@
+= Reset Signal Device Tree Bindings =
+
+This binding is intended to represent the hardware reset signals present
+internally in most IC (SoC, FPGA, ...) designs. Reset signals for whole
+standalone chips are most likely better represented as GPIOs, although there
+are likely to be exceptions to this rule.
+
+Hardware blocks typically receive a reset signal. This signal is generated by
+a reset provider (e.g. power management or clock module) and received by a
+reset consumer (the module being reset, or a module managing when a sub-
+ordinate module is reset). This binding exists to represent the provider and
+consumer, and provide a way to couple the two together.
+
+A reset signal is represented by the phandle of the provider, plus a reset
+specifier - a list of DT cells that represents the reset signal within the
+provider. The length (number of cells) and semantics of the reset specifier
+are dictated by the binding of the reset provider, although common schemes
+are described below.
+
+A word on where to place reset signal consumers in device tree: It is possible
+in hardware for a reset signal to affect multiple logically separate HW blocks
+at once. In this case, it would be unwise to represent this reset signal in
+the DT node of each affected HW block, since if activated, an unrelated block
+may be reset. Instead, reset signals should be represented in the DT node
+where it makes most sense to control it; this may be a bus node if all
+children of the bus are affected by the reset signal, or an individual HW
+block node for dedicated reset signals. The intent of this binding is to give
+appropriate software access to the reset signals in order to manage the HW,
+rather than to slavishly enumerate the reset signal that affects each HW
+block.
+
+= Reset providers =
+
+Required properties:
+#reset-cells:  Number of cells in a reset specifier; Typically 0 for nodes
+   with a single reset output and 1 for nodes with multiple
+   reset outputs.
+
+For example:
+
+   rst: reset-controller {
+   #reset-cells = <1>;
+   };
+
+= Reset consumers =
+
+Required properties:
+resets:List of phandle and reset specifier pairs, one pair
+   for each reset signal that affects the device, or that the
+   device manages. Note: if the reset provider specifies '0' for
+   #reset-cells, then only the phandle portion of the pair will
+   appear.
+
+Optional properties:
+reset-names:   List of reset signal name strings sorted in the same order as
+   the resets property. Consumers drivers will use reset-names to
+   match reset signal names with reset specifiers.
+
+For example:
+
+   device {
+   resets = < 20>;
+   reset-names = "reset";
+   };
+
+This represents a device with a single reset signal named "reset".
+
+   bus {
+   resets = < 10> < 11> < 12> < 11>;
+   reset-names = "i2s1", "i2s2", "dma", "mixer";
+   };
+
+This represents a bus that controls the reset signal of each of four sub-
+ordinate devices. Consider for example a bus that fails to operate unless no
+child device has reset asserted.
diff --git