Subject: Fwd: [PATCH] devicetree: bindings: separate CPU enable method descriptions

From: [email-masked] (Alex Elder)
Date: Wed, 07 May 2014 19:15:19 -0500

I neglected to copy linux-arm-kernel.	-Alex

-------- Original Message --------
Subject: [PATCH] devicetree: bindings: separate CPU enable method
descriptions
Date: Wed,  7 May 2014 18:23:53 -0500
From: Alex Elder <[email-masked]>
To: devicetree at vger.kernel.org
CC: mark.rutland at arm.com, sboyd at codeaurora.org, rvaswani at codeaurora.org,
linux-kernel at vger.kernel.org

The bindings for CPU enable methods are defined in ".../arm/cpus.txt".  As
additional 32-bit ARM CPUS are converted to use the "enable-method" CPU
property to imply a particular set of SMP operations to use, the list of
these
methods is likely to become unwieldy.  The current documentation already
contains several property descriptions that are meaningful only for certain
enable methods.

This patch defines a new Documentation subdirectory whose purpose is to give
each CPU enable method its own place to define how and when it's used, as
well as what other properties (optional or required) are associated with
the method.  The existing enable method documentation is expanded and moved
from ".../arm/cpus.txt" into new files accordingly.

Signed-off-by: Alex Elder <[email-masked]>
---
This series is available here:
	http://git.linaro.org/landing-teams/working/broadcom/kernel.git
        Branch review/enable-method-bindings

 .../bindings/arm/cpu-enable-method/README          | 20 +++++
 .../bindings/arm/cpu-enable-method/arm,psci.txt    | 69 ++++++++++++++++
 .../arm/cpu-enable-method/qcom,gcc-msm8660         | 30 +++++++
 .../arm/cpu-enable-method/qcom,kpss-acc-v1         | 56 +++++++++++++
 .../arm/cpu-enable-method/qcom,kpss-acc-v2         | 56 +++++++++++++
 .../bindings/arm/cpu-enable-method/spin-table.txt  | 96
++++++++++++++++++++++
 Documentation/devicetree/bindings/arm/cpus.txt     | 29 +------
 7 files changed, 330 insertions(+), 26 deletions(-)
 create mode 100644
Documentation/devicetree/bindings/arm/cpu-enable-method/README
 create mode 100644
Documentation/devicetree/bindings/arm/cpu-enable-method/arm,psci.txt
 create mode 100644
Documentation/devicetree/bindings/arm/cpu-enable-method/qcom,gcc-msm8660
 create mode 100644
Documentation/devicetree/bindings/arm/cpu-enable-method/qcom,kpss-acc-v1
 create mode 100644
Documentation/devicetree/bindings/arm/cpu-enable-method/qcom,kpss-acc-v2
 create mode 100644
Documentation/devicetree/bindings/arm/cpu-enable-method/spin-table.txt

diff --git
a/Documentation/devicetree/bindings/arm/cpu-enable-method/README
b/Documentation/devicetree/bindings/arm/cpu-enable-method/README
new file mode 100644
index 0000000..cc9431e
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/cpu-enable-method/README
@@ -0,0 +1,20 @@
+==========================
+CPU enable-method bindings
+==========================
+
+The device tree describes the layout of CPUs in a machine in a single
"cpus"
+node, which in turn contains a number of "cpu" sub-nodes defining
properties
+for each cpu.
+
+For multiprocessing configurations, CPU cores can be individually enabled
+and disabled.  The enabling capability is used for SMP startup as well as
+CPU hotplug.  A CPU enable method--normally specified in the device tree
+using an "enable-method" property--defines how cores are enabled.  If all
+CPUs in a machine use the same enable method and related property values,
+these properties should be defined in the "cpus" node, which associates the
+property values with all CPUs.  Alternatively, every "cpu" node can define
+its "enable-method" separately.
+
+Documents in this directory define how each of the CPU enable methods
are to
+be used, as well the names and possible values of related properties that
+are required by or affect each enable method.
diff --git
a/Documentation/devicetree/bindings/arm/cpu-enable-method/arm,psci.txt
b/Documentation/devicetree/bindings/arm/cpu-enable-method/arm,psci.txt
new file mode 100644
index 0000000..c80d68e
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/cpu-enable-method/arm,psci.txt
@@ -0,0 +1,69 @@
+====================================
+CPU enable-method "arm,psci" binding
+====================================
+
+This document describes the "arm,psci" method for enabling secondary CPUs.
+This is different from other CPU enable methods, in that CPU cores are
+enabled and disabled using the ARM PSCI interface, which is defined in the
+device tree independent of the CPUs.  Instead, a separate node compatible
+with "arm,psci" defines the PSCI functions supported; if a "cpu_on"
function
+is defined, that is used for enabling a CPU core.
+
+Enable method:		Distinct node with compatible = "arm,psci" property
+Compatible cpus:	(???)  (both 32- and 64-bit ARM have a hook)
+Properties:
+	- method
+		Usage:		required
+		Value type:	<string>
+		Definition:
+			A string defining the specific instruction
+			used to enable the core.  The value must be
+			either "hvc" or "smc".
+	- cpu_suspend
+		Usage:		optional
+		Value type:	<u32>
+		Definition:
+			If present, this value defines the PSCI function id
+			used to suspend execution on a CPU core.
+	- cpu_off
+		Usage:		optional
+		Value type:	<u32>
+		Definition:
+			If present, this value defines the PSCI function id
+			used to power down a CPU core.
+	- cpu_on
+		Usage:		optional
+		Value type:	<u32>
+		Definition:
+			If present, this value defines the PSCI function id
+			used to power up a CPU core.
+	- migrate
+		Usage:		optional
+		Value type:	<u32>
+		Definition:
+			If present, this value defines the PSCI function id
+			used to migrate context to a different CPU core.
+
+Example (contrived 2-core ARM Cortex-A57 64-bit system):
+
+	psci {
+		compatible = "arm,psci";
+		method = "smc";
+		cpu_on = 0x1;
+	};
+	cpus {
+		#size-cells = <0>;
+		#address-cells = <2>;
+
+		cpu at 0 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a57";	/* ??? */
+			reg = <0x0 0x0>;
+		};
+
+		cpu at 1 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a57";
+			reg = <0x0 0x1>;
+		};
+	};
diff --git
a/Documentation/devicetree/bindings/arm/cpu-enable-method/qcom,gcc-msm8660
b/Documentation/devicetree/bindings/arm/cpu-enable-method/qcom,gcc-msm8660
new file mode 100644
index 0000000..1e002d9
--- /dev/null
+++
b/Documentation/devicetree/bindings/arm/cpu-enable-method/qcom,gcc-msm8660
@@ -0,0 +1,30 @@
+======================================================
+Secondary CPU enable-method "qcom,gcc-msm8660" binding
+======================================================
+
+This document describes the "qcom,gcc-msm8660" method for enabling
+secondary CPUs.  A "qcom,gcc-msm8660" enable method should only be
+used in the "cpus" node, to apply to all CPUs.
+
+Enable method name:	"qcom,gcc-msm8660"
+Compatible cpu:		"qcom,scorpion"
+Related properties:	(none)
+
+Example:
+
+	cpus {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		compatible = "qcom,scorpion";
+		enable-method = "qcom,gcc-msm8660";
+
+		cpu at 0 {
+			device_type = "cpu";
+			reg = <0>;
+		};
+
+		cpu at 1 {
+			device_type = "cpu";
+			reg = <1>;
+		};
+	};
diff --git
a/Documentation/devicetree/bindings/arm/cpu-enable-method/qcom,kpss-acc-v1
b/Documentation/devicetree/bindings/arm/cpu-enable-method/qcom,kpss-acc-v1
new file mode 100644
index 0000000..3f6ce56
--- /dev/null
+++
b/Documentation/devicetree/bindings/arm/cpu-enable-method/qcom,kpss-acc-v1
@@ -0,0 +1,56 @@
+======================================================
+Secondary CPU enable-method "qcom,kpss-acc-v1" binding
+======================================================
+
+This document describes the "qcom,kpss-acc-v1" method for enabling CPUs.
+This enable method can be used in either the "cpus" node or in individual
+"cpu" nodes.  Note that each "cpu" node must have both "qcom,saw" and
+"qcom,acc" properties defined (even if the "enable-method" property was
+defined only in the "cpus" node).
+
+Enable method name:	"qcom,kpss-acc-v1"
+Compatible machine:	"qcom,msm8960"
+Compatible cpu:		"qcom,krait"
+Related properties:
+	- qcom,saw
+		Usage:		required (in each "cpu" node")
+		Value type:	<phandle>
+		Definition:
+			Specifies the SAW[1] node associated with this CPU.
+
+	- qcom,acc
+		Usage:		required (in each "cpu" node")
+		Value type:	<phandle>
+		Definition:
+			Specifies the ACC[2] node associated with this CPU.
+
+Example:
+
+/ {
+	compatible = "qcom,msm8960";
+
+	cpus {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		compatible = "qcom,krait";
+		enable-method = "qcom,kpss-acc-v1";
+
+		cpu at 0 {
+			device_type = "cpu";
+			reg = <0>;
+			qcom,acc = <&acc0>;
+			qcom,saw = <&saw0>;
+		};
+
+		cpu at 1 {
+			device_type = "cpu";
+			reg = <1>;
+			qcom,acc = <&acc1>;
+			qcom,saw = <&saw1>;
+		};
+	};
+};
+
+--
+[1] arm/msm/qcom,saw2.txt
+[2] arm/msm/qcom,kpss-acc.txt
diff --git
a/Documentation/devicetree/bindings/arm/cpu-enable-method/qcom,kpss-acc-v2
b/Documentation/devicetree/bindings/arm/cpu-enable-method/qcom,kpss-acc-v2
new file mode 100644
index 0000000..4368d904
--- /dev/null
+++
b/Documentation/devicetree/bindings/arm/cpu-enable-method/qcom,kpss-acc-v2
@@ -0,0 +1,56 @@
+======================================================
+Secondary CPU enable-method "qcom,kpss-acc-v2" binding
+======================================================
+
+This document describes the "qcom,kpss-acc-v2" method for enabling CPUs.
+This enable method can be used in either the "cpus" node or in individual
+"cpu" nodes.  Note that each "cpu" node must have both "qcom,saw" and
+"qcom,acc" properties defined (even if the "enable-method" property was
+defined only in the "cpus" node).
+
+Enable method name:	"qcom,kpss-acc-v2"
+Compatible machine:	"qcom,msm8974"
+Compatible cpu:		"qcom,krait"
+Related properties:
+	- qcom,saw
+		Usage:		required (in each "cpu" node")
+		Value type:	<phandle>
+		Definition:
+			Specifies the SAW[1] node associated with this CPU.
+
+	- qcom,acc
+		Usage:		required (in each "cpu" node")
+		Value type:	<phandle>
+		Definition:
+			Specifies the ACC[2] node associated with this CPU.
+
+Example:
+
+/ {
+	compatible = "qcom,msm8974";
+
+	cpus {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		compatible = "qcom,krait";
+		enable-method = "qcom,kpss-acc-v2";
+
+		cpu at 0 {
+			device_type = "cpu";
+			reg = <0>;
+			qcom,acc = <&acc0>;
+			qcom,saw = <&saw0>;
+		};
+
+		cpu at 1 {
+			device_type = "cpu";
+			reg = <1>;
+			qcom,acc = <&acc1>;
+			qcom,saw = <&saw1>;
+		};
+	};
+};
+
+--
+[1] arm/msm/qcom,saw2.txt
+[2] arm/msm/qcom,kpss-acc.txt
diff --git
a/Documentation/devicetree/bindings/arm/cpu-enable-method/spin-table.txt
b/Documentation/devicetree/bindings/arm/cpu-enable-method/spin-table.txt
new file mode 100644
index 0000000..f57955a
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/cpu-enable-method/spin-table.txt
@@ -0,0 +1,96 @@
+================================================
+Secondary CPU enable-method "spin-table" binding
+================================================
+
+This document describes the "spin-table" method for enabling secondary
CPUs.
+See the "README" file in this directory for more information on CPU enable
+methods.  A "spin-table" enable method can be used in either the "cpus"
node
+or in individual "cpu" nodes.
+
+Enable method name:	"spin-table"
+Compatible cpus:	"arm,cortex-a57" (?)
+Related properties:
+	- cpu-release-addr
+		Usage:		required
+		Value type:	<prop-encoded-array>
+		Definition:
+			A two cell value identifying a 64-bit memory location
+			used by the boot CPU to inform a secondary CPU it
+			should begin its kernel bootstrap.  Memory at this
+			location must initially be zeroed.
+
+Examples (contrived 4-core ARM Cortex-A57 64-bit systems):
+
+The first example uses the same enable method for all cores.
+
+	cpus {
+		#size-cells = <0>;
+		#address-cells = <2>;
+		enable-method = "spin-table";
+		cpu-release-addr = <0 0x20000000>;
+
+		cpu at 0 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a57";
+			reg = <0x0 0x0>;
+		};
+
+		cpu at 1 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a57";
+			reg = <0x0 0x1>;
+		};
+
+		cpu at 100 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a57";
+			reg = <0x0 0x100>;
+		};
+
+		cpu at 101 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a57";
+			reg = <0x0 0x101>;
+		};
+	};
+
+
+The second example uses specifies distinct enable method properties for
each
+CPU core.
+
+	cpus {
+		#size-cells = <0>;
+		#address-cells = <2>;
+
+		cpu at 0 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a57";
+			reg = <0x0 0x0>;
+			enable-method = "spin-table";
+			cpu-release-addr = <0 0x20000000>;
+		};
+
+		cpu at 1 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a57";
+			reg = <0x0 0x1>;
+			enable-method = "spin-table";
+			cpu-release-addr = <0 0x20000008>;
+		};
+
+		cpu at 100 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a57";
+			reg = <0x0 0x100>;
+			enable-method = "spin-table";
+			cpu-release-addr = <0 0x20000010>;
+		};
+
+		cpu at 101 {
+			device_type = "cpu";
+			compatible = "arm,cortex-a57";
+			reg = <0x0 0x101>;
+			enable-method = "spin-table";
+			cpu-release-addr = <0 0x20000018>;
+		};
+	};
diff --git a/Documentation/devicetree/bindings/arm/cpus.txt
b/Documentation/devicetree/bindings/arm/cpus.txt
index 333f4ae..2bb2a3e 100644
--- a/Documentation/devicetree/bindings/arm/cpus.txt
+++ b/Documentation/devicetree/bindings/arm/cpus.txt
@@ -185,30 +185,8 @@ nodes to be present and contain the properties
described below.
 			    "qcom,gcc-msm8660"
 			    "qcom,kpss-acc-v1"
 			    "qcom,kpss-acc-v2"
-
-	- cpu-release-addr
-		Usage: required for systems that have an "enable-method"
-		       property value of "spin-table".
-		Value type: <prop-encoded-array>
-		Definition:
-			# On ARM v8 64-bit systems must be a two cell
-			  property identifying a 64-bit zero-initialised
-			  memory location.
-
-	- qcom,saw
-		Usage: required for systems that have an "enable-method"
-		       property value of "qcom,kpss-acc-v1" or
-		       "qcom,kpss-acc-v2"
-		Value type: <phandle>
-		Definition: Specifies the SAW[1] node associated with this CPU.
-
-	- qcom,acc
-		Usage: required for systems that have an "enable-method"
-		       property value of "qcom,kpss-acc-v1" or
-		       "qcom,kpss-acc-v2"
-		Value type: <phandle>
-		Definition: Specifies the ACC[2] node associated with this CPU.
-
+		Details about use of these CPU enable methods is documented
+		elsewhere[1].

 Example 1 (dual-cluster big.LITTLE system 32-bit):

@@ -403,5 +381,4 @@ cpus {
 };

 --
-[1] arm/msm/qcom,saw2.txt
-[2] arm/msm/qcom,kpss-acc.txt
+[1] arm/cpu-enable-method/
-- 
1.9.1

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