regulator: Introduce TI Adaptive Body Bias(ABB) on-chip LDO driver

Adaptive Body Biasing (ABB) modulates transistor bias voltages
dynamically in order to optimize switching speed versus leakage.

Texas Instruments' SmartReflex 2 technology provides support for this
power management technique with Forward Body Biasing (FBB) and Reverse
Body Biasing (RBB). These modulate the body voltage of transistor
cells or blocks dynamically to gain performance and reduce leakage.
TI's SmartReflex white paper[1] has further information for usage in
conjunction with other power management techniques.

The application of FBB/RBB technique is determined for each unique
device in some process nodes, whereas, they are mandated on other
process nodes.

In a nutshell, ABB technique is implemented on TI SoC as an on-chip
LDO which has ABB module controlling the bias voltage. However, the
voltage is unique per device. These vary per SoC family and the manner
in which these techniques are used may vary depending on the Operating
Performance Point (OPP) voltage targeted. For example:
OMAP3630/OMAP4430: certain OPPs mandate usage of FBB independent of
	devices.
OMAP4460/OMAP4470: certain OPPs mandate usage of FBB, while others may
	optionally use FBB or optimization with RBB.
OMAP5: ALL OPPs may optionally use ABB, and ABB biasing voltage is
	influenced by vset fused in s/w and requiring s/w override of
	default values.

Further, two generations of ABB module are used in various TI SoCs.
They have remained mostly register field compatible, however the
register offset had switched between versions.

We introduce ABB LDO support in the form of a regulator which is
controlled by voltages denoting the desired Operating Performance
Point which is targeted. However, since ABB transition is part of OPP
change sequence, the sequencing required to ensure sane operation
w.r.t OPP change is left to the controlling driver (example: cpufreq
SoC driver) using standard regulator operations.

The driver supports all ABB modes and ability to override ABB LDO vset
control efuse based ABB mode detection etc.

Current implementation is heavily influenced by the original patch
series [2][3] from Mike Turquette. However, the current implementation
supports only device tree based information.

[1] http://www.ti.com/pdfs/wtbu/smartreflex_whitepaper.pdf
[2] http://marc.info/?l=linux-omap&m=134931341818379&w=2
[3] http://marc.info/?l=linux-arm-kernel&m=134931402406853&w=2

[nm@ti.com: co-developer]
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Andrii.Tseglytskyi <andrii.tseglytskyi@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

Documentation/devicetree/bindings/regulator/ti-abb-regulator.txt

+Adaptive Body Bias(ABB) SoC internal LDO regulator for Texas Instruments SoCs
+
+Required Properties:
+- compatible: Should be one of:
+  - "ti,abb-v1" for older SoCs like OMAP3
+  - "ti,abb-v2" for newer SoCs like OMAP4, OMAP5
+- reg: Address and length of the register set for the device. It contains
+  the information of registers in the same order as described by reg-names
+- reg-names: Should contain the reg names
+  - "base-address"	- contains base address of ABB module
+  - "int-address"	- contains address of interrupt register for ABB module
+  (also see Optional properties)
+- #address-cell: should be 0
+- #size-cell: should be 0
+- clocks: should point to the clock node used by ABB module
+- ti,settling-time: Settling time in uSecs from SoC documentation for ABB module
+	to settle down(target time for SR2_WTCNT_VALUE).
+- ti,clock-cycles: SoC specific data about count of system ti,clock-cycles used for
+	computing settling time from SoC Documentation for ABB module(clock
+	cycles for SR2_WTCNT_VALUE).
+- ti,tranxdone-status-mask: Mask to the int-register to write-to-clear mask
+	indicating LDO tranxdone (operation complete).
+- ti,abb_info: An array of 6-tuples u32 items providing information about ABB
+	configuration needed per operational voltage of the device.
+	Each item consists of the following in the same order:
+	volt: voltage in uV - Only used to index ABB information.
+	ABB mode: one of the following:
+		0-bypass
+		1-Forward Body Bias(FBB)
+		3-Reverse Body Bias(RBB)
+	efuse:	(see Optional properties)
+	RBB enable efuse Mask:	(See Optional properties)
+	FBB enable efuse Mask:	(See Optional properties)
+	Vset value efuse Mask:	(See Optional properties)
+
+	NOTE: If more than 1 entry is present, then regulator is setup to change
+	      voltage, allowing for various modes to be selected indexed off
+	      the regulator. Further, ABB LDOs are considered always-on by
+	      default.
+
+Optional Properties:
+- reg-names: In addition to the required properties, the following are optional
+  - "efuse-address"	- Contains efuse base address used to pick up ABB info.
+  - "ldo-address"	- Contains address of ABB LDO overide register address.
+	"efuse-address" is required for this.
+- ti,ldovbb-vset-mask	- Required if ldo-address is set, mask for LDO override
+	register to provide override vset value.
+- ti,ldovbb-override-mask - Required if ldo-address is set, mask for LDO
+	override register to enable override vset value.
+- ti,abb_opp_sel: Addendum to the description in required properties
+	efuse: Mandatory if 'efuse-address' register is defined. Provides offset
+	       from efuse-address to pick up ABB characteristics. Set to 0 if
+	       'efuse-address' is not defined.
+	RBB enable efuse Mask:	Optional if 'efuse-address' register is defined.
+		'ABB mode' is force set to RBB mode if value at "efuse-address"
+		+ efuse maps to RBB mask. Set to 0 to ignore this.
+	FBB enable efuse Mask:	Optional if 'efuse-address' register is defined.
+		'ABB mode' is force set to FBB mode if value at "efuse-address"
+		+ efuse maps to FBB mask (valid only if RBB mask does not match)
+		Set to 0 to ignore this.
+	Vset value efuse Mask:	Mandatory if ldo-address is set. Picks up from
+		efuse the value to set in 'ti,ldovbb-vset-mask' at ldo-address.
+
+Example #1: Simplest configuration (no efuse data, hard coded ABB table):
+abb_x: regulator-abb-x {
+	compatible = "ti,abb-v1";
+	regulator-name = "abb_x";
+	#address-cell = <0>;
+	#size-cells = <0>;
+	reg = <0x483072f0 0x8>, <0x48306818 0x4>;
+	reg-names = "base-address", "int-address";
+	ti,tranxdone-status-mask = <0x4000000>;
+	clocks = <&sysclk>;
+	ti,settling-time = <30>;
+	ti,clock-cycles = <8>;
+	ti,abb_info = <
+	/* uV		ABB	efuse	rbb_m	fbb_m	vset_m */
+	1012500		0	0	0	0	0 /* Bypass */
+	1200000		3	0	0	0	0 /* RBB mandatory */
+	1320000		1	0	0	0	0 /* FBB mandatory */
+	>;
+};
+
+Example #2: Efuse bits contain ABB mode setting (no LDO override capability)
+abb_y: regulator-abb-y {
+	compatible = "ti,abb-v2";
+	regulator-name = "abb_y";
+	#address-cell = <0>;
+	#size-cells = <0>;
+	reg = <0x4a307bd0 0x8>, <0x4a306014 0x4>, <0x4A002268 0x8>;
+	reg-names = "base-address", "int-address", "efuse-address";
+	ti,tranxdone-status-mask = <0x4000000>;
+	clocks = <&sysclk>;
+	ti,settling-time = <50>;
+	ti,clock-cycles = <16>;
+	ti,abb_info = <
+	/* uV		ABB	efuse	rbb_m	fbb_m	vset_m */
+	975000		0	0	0	0	0 /* Bypass */
+	1012500		0	0	0x40000	0	0 /* RBB optional */
+	1200000		0	0x4	0	0x40000	0 /* FBB optional */
+	1320000		1	0	0	0	0 /* FBB mandatory */
+	>;
+};
+
+Example #3: Efuse bits contain ABB mode setting and LDO override capability
+abb_z: regulator-abb-z {
+	compatible = "ti,abb-v2";
+	regulator-name = "abb_z";
+	#address-cell = <0>;
+	#size-cells = <0>;
+	reg = <0x4ae07ce4 0x8>, <0x4ae06010 0x4>,
+	      <0x4a002194 0x8>, <0x4ae0C314 0x4>;
+	reg-names = "base-address", "int-address",
+		    "efuse-address", "ldo-address";
+	ti,tranxdone-status-mask = <0x8000000>;
+	/* LDOVBBMM_MUX_CTRL */
+	ti,ldovbb-override-mask = <0x400>;
+	/* LDOVBBMM_VSET_OUT */
+	ti,ldovbb-vset-mask = <0x1F>;
+	clocks = <&sysclk>;
+	ti,settling-time = <50>;
+	ti,clock-cycles = <16>;
+	ti,abb_info = <
+	/* uV	ABB	efuse	rbb_m	fbb_m	vset_m */
+	975000	0	0	0	0	0	/* Bypass */
+	1200000	0	0x4	0	0x40000	0x1f00	/* FBB optional, vset */
+	>;
+};

drivers/regulator/Kconfig

@@ -472,6 +472,16 @@ config REGULATOR_TWL4030
 	  This driver supports the voltage regulators provided by
 	  this family of companion chips.
 
+config REGULATOR_TI_ABB
+	bool "TI Adaptive Body Bias on-chip LDO"
+	depends on ARCH_OMAP
+	help
+	  Select this option to support Texas Instruments' on-chip Adaptive Body
+	  Bias (ABB) LDO regulators. It is recommended that this option be
+	  enabled on required TI SoC. Certain Operating Performance Points
+	  on TI SoCs may be unstable without enabling this as it provides
+	  device specific optimized bias to allow/optimize functionality.
+
 config REGULATOR_VEXPRESS
 	tristate "Versatile Express regulators"
 	depends on VEXPRESS_CONFIG

drivers/regulator/Makefile

@@ -63,6 +63,7 @@ obj-$(CONFIG_REGULATOR_TPS65910) += tps65910-regulator.o
 obj-$(CONFIG_REGULATOR_TPS65912) += tps65912-regulator.o
 obj-$(CONFIG_REGULATOR_TPS80031) += tps80031-regulator.o
 obj-$(CONFIG_REGULATOR_TWL4030) += twl-regulator.o
+obj-$(CONFIG_REGULATOR_TI_ABB) += ti-abb-regulator.o
 obj-$(CONFIG_REGULATOR_VEXPRESS) += vexpress.o
 obj-$(CONFIG_REGULATOR_WM831X) += wm831x-dcdc.o
 obj-$(CONFIG_REGULATOR_WM831X) += wm831x-isink.o