[PATCH V3 1/2] pinctrl: tegra: Add DT binding for io pads control

[Laxman Dewangan <ldewangan@xxxxxxxxxx>]

NVIDIA Tegra124 and later SoCs support the multi-voltage level and
low power state of some of its IO pads. The IO pads can work in
the voltage of the 1.8V and 3.3V of IO voltage from IO power rail
sources. When IO interfaces are not used then IO pads can be
configure in low power state to reduce the power consumption from
that IO pads.

On Tegra124, the voltage level of IO power rail source is auto
detected by hardware(SoC) and hence it is only require to configure
in low power mode if IO pads are not used.

On T210 onwards, the auto-detection of voltage level from IO power
rail is removed from SoC and hence SW need to configure the PMC
register explicitly to set proper voltage in IO pads based on
IO rail power source voltage.

Add DT binding document for detailing the DT properties for
configuring IO pads voltage levels and its power state.

Signed-off-by: Laxman Dewangan <ldewangan@xxxxxxxxxx>

---
Changes from V1:
 New in series based on pinctrl driver requirement.

Changes from V2:
 Updated the statement to say 1.8V and 3.3V as nominal voltage.
 Corrected DT example by adding -supply and taken care of V2 review
 from Rob.
---
 .../bindings/pinctrl/nvidia,tegra-io-pad.txt       | 126 +++++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pinctrl/nvidia,tegra-io-pad.txt

diff --git a/Documentation/devicetree/bindings/pinctrl/nvidia,tegra-io-pad.txt b/Documentation/devicetree/bindings/pinctrl/nvidia,tegra-io-pad.txt
new file mode 100644
index 0000000..a88c484
--- /dev/null
+++ b/Documentation/devicetree/bindings/pinctrl/nvidia,tegra-io-pad.txt
@@ -0,0 +1,126 @@
+NVIDIA Tegra PMC IO pad controller
+
+NVIDIA Tegra124 and later SoCs support the multi-voltage level and low power
+state of some of its IO pads. When IO interface are not used then IO pads can
+be configure in low power state to reduce the power from that IO pads. The IO
+pads can work in the nominal IO voltage of 1.8V and 3.3V from power rail
+sources.
+
+On Tegra124, the voltage of IO power rail source is auto detected by SoC and
+hence it is only require to configure in low power mode if IO pads are not
+used.
+
+On T210 onwards, the HW based auto-detection for IO voltage is removed and
+hence SW need to configure the PMC register explicitly, to set proper voltage
+in IO pads, based on IO rail power source voltage.
+
+The voltage configurations and low power state of IO pads should be done in
+boot if it is not going to change otherwise dynamically based on IO rail
+voltage on that IO pads and usage of IO pads
+
+The DT property of the IO pads must be under the node of pmc i.e.
+pmc@7000e400 for Tegra124 onwards.
+
+Please refer to <pinctrl-bindings.txt> in this directory for details of the
+common pinctrl bindings used by client devices, including the meaning of the
+phrase "pin configuration node".
+
+Tegra's pin configuration nodes act as a container for an arbitrary number of
+subnodes. Each of these subnodes represents some desired configuration for an
+IO pads, or a list of IO pads. This configuration can include the voltage and
+power enable/disable control
+
+The name of each subnode is not important; all subnodes should be enumerated
+and processed purely based on their content. Each subnode only affects those
+parameters that are explicitly listed. Unspecified is represented as an absent
+property,
+
+See the TRM to determine which properties and values apply to each IO pads.
+
+Required subnode-properties:
+==========================
+- pins : An array of strings. Each string contains the name of an IO pads. Valid
+	 values for these names are listed below.
+
+Optional subnode-properties:
+==========================
+Following properties are supported from generic pin configuration explained
+in <dt-bindings/pinctrl/pinctrl-binding.txt>.
+low-power-enable:		enable low power mode.
+low-power-disable:		disable low power mode.
+
+Valid values for pin for T124 are:
+	audio, bb, cam, comp, csia, csib, csie, dsi, dsib, dsic, dsid, hdmi,
+	hsic, hv, lvds, mipi-bias, nand, pex-bias, pex-clk1, pex-clk2,
+	pex-ctrl, sdmmc1, sdmmc3, sdmmc4, sys-ddc, uart, usb0, usb1, usb2,
+	usb-bias
+
+Valid values for pin for T210 are:
+	audio, audio-hv, cam, csia, csib, csic, csid, csie, csif,
+	dbg, debug-nonao, dmic, dp, dsi, dsib, dsic, dsid, emmc, emmc2,
+	gpio, hdmi, hsic, lvds, mipi-bias, pex-bias, pex-clk1, pex-clk2,
+	pex-ctrl, sdmmc1, sdmmc3, spi, spi-hv, uart, usb-bias, usb0,
+	usb1, usb2, usb3.
+
+To find out the IO rail voltage for setting the voltage of IO pad by SW,
+the regulator supply handle must provided from the DT and it is explained
+in the regulator DT binding document
+	<devicetree/bindings/regulator/regulator.txt>.
+For example, for GPIO rail the supply name is vddio-gpio and regulator
+handle is supplied from DT as
+	vddio-gpio-supply = <&regulator_xyz>;
+
+For T210, following IO pads support the 1.8V/3.3V and the corresponding
+IO voltage pin names are as follows:
+	audio -> vddio-audio
+	audio-hv -> vddio-audio-hv
+	cam ->vddio-cam
+	dbg -> vddio-dbg
+	dmic -> vddio-dmic
+	gpio -> vddio-gpio
+	pex-ctrl -> vddio-pex-ctrl
+	sdmmc1 -> vddio-sdmmc1
+	sdmmc3 -> vddio-sdmmc3
+	spi -> vddio-spi
+	spi-hv -> vddio-spi-hv
+	uart -> vddio-uart
+
+Example:
+	i2c@7000d000 {
+		pmic@3c {
+			regulators {
+				vddio_sdmmc1: ldo2 {
+					/* Regulator entries for LDO2 */
+				};
+
+				vdd_cam: ldo3 {
+					/* Regulator entries for LDO3 */
+				};
+			};
+		};
+	};
+
+	pmc@7000e400 {
+		vddio-cam-supply = <&vdd_cam>;
+		vddio-sdmmc1-supply = <&vddio_sdmmc1>;
+
+		pinctrl-names = "default";
+		pinctrl-0 = <&tegra_io_pad_volt_default>;
+		tegra_io_pad_volt_default: common {
+			audio-hv {
+				pins = "audio-hv";
+				low-power-disable;
+			};
+
+			gpio {
+				pins = "gpio";
+				low-power-disable;
+			};
+
+			audio {
+				pins = "audio", "dmic", "sdmmc3";
+				low-power-enable;
+			};
+		};
+
+	};
-- 
2.1.4

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