dt-bindings: Add a document of PECI adapter driver for ASPEED AST24xx/25xx SoCs

This commit adds a dt-bindings document of PECI adapter driver for ASPEED
AST24xx/25xx SoCs.

OpenBMC-Staging-Count: 2
Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
Reviewed-by: Haiyue Wang <haiyue.wang@linux.intel.com>
Reviewed-by: James Feist <james.feist@linux.intel.com>
Reviewed-by: Vernon Mauery <vernon.mauery@linux.intel.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Joel Stanley <joel@jms.id.au>

1 files changed, 55 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/peci/peci-aspeed.txt b/Documentation/devicetree/bindings/peci/peci-aspeed.txt
new file mode 100644
index 000000000000..cdca73a3b7d8
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+++ b/Documentation/devicetree/bindings/peci/peci-aspeed.txt
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+Device tree configuration for PECI buses on the AST24XX and AST25XX SoCs.
+
+Required properties:
+- compatible        : Should be one of:
+			"aspeed,ast2400-peci"
+			"aspeed,ast2500-peci"
+- reg               : Should contain PECI controller registers location and
+		      length.
+- #address-cells    : Should be <1> required to define a client address.
+- #size-cells       : Should be <0> required to define a client address.
+- interrupts        : Should contain PECI controller interrupt.
+- clocks            : Should contain clock source for PECI controller. Should
+		      reference the external oscillator clock in the second
+		      cell.
+- resets            : Should contain phandle to reset controller with the reset
+		      number in the second cell.
+- clock-frequency   : Should contain the operation frequency of PECI controller
+		      in units of Hz.
+		      187500 ~ 24000000
+
+Optional properties:
+- msg-timing        : Message timing negotiation period. This value will
+		      determine the period of message timing negotiation to be
+		      issued by PECI controller. The unit of the programmed
+		      value is four times of PECI clock period.
+		      0 ~ 255 (default: 1)
+- addr-timing       : Address timing negotiation period. This value will
+		      determine the period of address timing negotiation to be
+		      issued by PECI controller. The unit of the programmed
+		      value is four times of PECI clock period.
+		      0 ~ 255 (default: 1)
+- rd-sampling-point : Read sampling point selection. The whole period of a bit
+		      time will be divided into 16 time frames. This value will
+		      determine the time frame in which the controller will
+		      sample PECI signal for data read back. Usually in the
+		      middle of a bit time is the best.
+		      0 ~ 15 (default: 8)
+- cmd-timeout-ms    : Command timeout in units of ms.
+		      1 ~ 60000 (default: 1000)
+
+Example:
+	peci0: peci-bus@0 {
+		compatible = "aspeed,ast2500-peci";
+		reg = <0x0 0x60>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+		interrupts = <15>;
+		clocks = <&syscon ASPEED_CLK_GATE_REFCLK>;
+		resets = <&syscon ASPEED_RESET_PECI>;
+		clock-frequency = <24000000>;
+		msg-timing = <1>;
+		addr-timing = <1>;
+		rd-sampling-point = <8>;
+		cmd-timeout-ms = <1000>;
+	};