linux-kernel - [PATCH v3 3/5] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock

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Message-Id: <20210717123829.5201-4-pali@kernel.org>
Date:   Sat, 17 Jul 2021 14:38:27 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "Andrew Lunn" <andrew@...n.ch>,
        "Gregory Clement" <gregory.clement@...tlin.com>,
        "Sebastian Hesselbarth" <sebastian.hesselbarth@...il.com>,
        "Vladimir Vid" <vladimir.vid@...tura.hr>,
        Marek Behún <kabel@...nel.org>,
        "Geert Uytterhoeven" <geert@...ux-m68k.org>,
        linux-clk@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v3 3/5] dt-bindings: mvebu-uart: document DT bindings for marvell,armada-3700-uart-clock

This change adds DT bindings documentation for device nodes with compatible
string "marvell,armada-3700-uart-clock".

Signed-off-by: Pali Rohár <pali@...nel.org>
---
 .../bindings/clock/armada3700-uart-clock.txt  | 24 +++++++++++++++++++
 .../devicetree/bindings/serial/mvebu-uart.txt |  9 ++++---
 2 files changed, 30 insertions(+), 3 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/clock/armada3700-uart-clock.txt

diff --git a/Documentation/devicetree/bindings/clock/armada3700-uart-clock.txt b/Documentation/devicetree/bindings/clock/armada3700-uart-clock.txt
new file mode 100644
index 000000000000..144bc6d7eae8
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/armada3700-uart-clock.txt
@@ -0,0 +1,24 @@
+* Marvell Armada 3720 UART clocks
+
+Required properties:
+- compatible: "marvell,armada-3700-uart-clock"
+- reg: two 4-bytes registers: UART Clock Control and UART 2 Baud Rate Divisor
+- #clock-cells : from common clock binding; shall be set to 1
+- clocks: List of parent clocks suitable for UART from following set:
+		"TBG-A-P", "TBG-B-P", "TBG-A-S", "TBG-B-S", "xtal"
+	UART clock can use one from this set and when more are provided
+	then kernel would choose and configure the most suitable one.
+	It is suggest to specify at least one TBG clock to achieve
+	baudrates above 230400 and also to specify clock which bootloader
+	used for UART (most probably xtal) for smooth boot log on UART.
+
+Example:
+	uartclk: uartclk@...00 {
+		compatible = "marvell,armada-3700-uart-clock";
+		reg = <0x12010 0x4>, <0x12210 0x4>;
+		clocks = <&tbg 0>, <&tbg 1>, <&tbg 2>,
+			<&tbg 3>, <&xtalclk>;
+		clock-names = "TBG-A-P", "TBG-B-P", "TBG-A-S",
+			"TBG-B-S", "xtal";
+		#clock-cells = <1>;
+	};
diff --git a/Documentation/devicetree/bindings/serial/mvebu-uart.txt b/Documentation/devicetree/bindings/serial/mvebu-uart.txt
index 2d0dbdf32d1d..463968e7e7f3 100644
--- a/Documentation/devicetree/bindings/serial/mvebu-uart.txt
+++ b/Documentation/devicetree/bindings/serial/mvebu-uart.txt
@@ -14,7 +14,10 @@ Required properties:
       is provided (possible only with the "marvell,armada-3700-uart"
       compatible string for backward compatibility), it will only work
       if the baudrate was initialized by the bootloader and no baudrate
-      change will then be possible.
+      change will then be possible. When provided it should be UART1-clk
+      for standard variant of UART and UART2-clk for extended variant
+      of UART. TBG clock (with TBG divisors d1=d2=1) or xtal clock should
+      not be used and are supported only for backward compatibility.
 - interrupts:
     - Must contain three elements for the standard variant of the IP
       (marvell,armada-3700-uart): "uart-sum", "uart-tx" and "uart-rx",
@@ -34,7 +37,7 @@ Example:
 	uart0: serial@...00 {
 		compatible = "marvell,armada-3700-uart";
 		reg = <0x12000 0x18>;
-		clocks = <&xtalclk>;
+		clocks = <&uartclk 0>;
 		interrupts =
 		<GIC_SPI 11 IRQ_TYPE_LEVEL_HIGH>,
 		<GIC_SPI 12 IRQ_TYPE_LEVEL_HIGH>,
@@ -45,7 +48,7 @@ Example:
 	uart1: serial@...00 {
 		compatible = "marvell,armada-3700-uart-ext";
 		reg = <0x12200 0x30>;
-		clocks = <&xtalclk>;
+		clocks = <&uartclk 1>;
 		interrupts =
 		<GIC_SPI 30 IRQ_TYPE_EDGE_RISING>,
 		<GIC_SPI 31 IRQ_TYPE_EDGE_RISING>;
-- 
2.20.1