linux-kernel - [PATCH net-next 5/5] arm64: dts: ti: k3-am625-sk: Add cpsw3g cpts PPS support

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Message-ID: <20230111114429.1297557-6-s-vadapalli@ti.com>
Date:   Wed, 11 Jan 2023 17:14:29 +0530
From:   Siddharth Vadapalli <s-vadapalli@...com>
To:     <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski@...aro.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <nm@...com>,
        <kristo@...nel.org>, <vigneshr@...com>, <rogerq@...nel.org>,
        <nsekhar@...com>
CC:     <netdev@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <srk@...com>,
        <s-vadapalli@...com>
Subject: [PATCH net-next 5/5] arm64: dts: ti: k3-am625-sk: Add cpsw3g cpts PPS support

The CPTS driver is capable of configuring GENFy (Periodic Signal Generator
Function) present in the CPTS module, to generate periodic output signals
with a custom time period. In order to generate a PPS signal on the GENFy
output, the device-tree property "ti,pps" has to be used. The "ti,pps"
property is used to declare the mapping between the CPTS HWx_TS_PUSH
(Hardware Timestamp trigger) input and the GENFy output that is configured
to generate a PPS signal. The mapping is of the form:
<x-1 y>
where the value x corresponds to HWx_TS_PUSH input (1-based indexing) and
the value y corresponds to GENFy (0-based indexing).

To verify that the signal is a PPS signal, the GENFy output signal is fed
into the CPTS HWx_TS_PUSH input, which generates a timestamp event on the
rising edge of the GENFy signal. The GENFy output signal can be routed to
the HWx_TS_PUSH input by using the Time Sync Router. This is done by
mentioning the mapping between the GENFy output and the HWx_TS_PUSH input
within the "timesync_router" device-tree node.

The Input Sources to the Time Sync Router are documented at: [1]
The Output Destinations of the Time Sync Router are documented at: [2]

The PPS signal can be verified using testptp and ppstest tools as follows:
 # ./testptp -d /dev/ptp0 -P 1
 pps for system time request okay
 # ./ppstest /dev/pps0
 trying PPS source "/dev/pps0"
 found PPS source "/dev/pps0"
 ok, found 1 source(s), now start fetching data...
 source 0 - assert 48.000000013, sequence: 8 - clear  0.000000000, sequence: 0
 source 0 - assert 49.000000013, sequence: 9 - clear  0.000000000, sequence: 0
 source 0 - assert 50.000000013, sequence: 10 - clear  0.000000000, sequence: 0

Add an example in the device-tree, enabling PPS generation on GENF1. The
HW3_TS_PUSH Timestamp trigger input is used to verify the PPS signal.

[1]
Link: https://software-dl.ti.com/tisci/esd/latest/5_soc_doc/am62x/interrupt_cfg.html#timesync-event-router0-interrupt-router-input-sources
[2]
Link: https://software-dl.ti.com/tisci/esd/latest/5_soc_doc/am62x/interrupt_cfg.html#timesync-event-router0-interrupt-router-output-destinations

Signed-off-by: Siddharth Vadapalli <s-vadapalli@...com>
---
 arch/arm64/boot/dts/ti/k3-am625-sk.dts | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/arm64/boot/dts/ti/k3-am625-sk.dts b/arch/arm64/boot/dts/ti/k3-am625-sk.dts
index 4f179b146cab..962a922cc94b 100644
--- a/arch/arm64/boot/dts/ti/k3-am625-sk.dts
+++ b/arch/arm64/boot/dts/ti/k3-am625-sk.dts
@@ -366,6 +366,10 @@ &cpsw3g {
 	pinctrl-names = "default";
 	pinctrl-0 = <&main_rgmii1_pins_default
 		     &main_rgmii2_pins_default>;
+
+	cpts@...00 {
+		ti,pps = <2 1>;
+	};
 };

 &cpsw_port1 {
@@ -464,3 +468,19 @@ partition@...0000 {
 		};
 	};
 };
+
+#define TS_OFFSET(pa, val)	(0x4+(pa)*4) (0x10000 | val)
+
+&timesync_router {
+	status = "okay";
+	pinctrl-names = "default";
+	pinctrl-0 = <&cpsw_cpts>;
+
+	/* Example of the timesync routing */
+	cpsw_cpts: cpsw-cpts {
+		pinctrl-single,pins = <
+			/* pps [cpsw cpts genf1] in17 -> out12 [cpsw cpts hw3_push] */
+			TS_OFFSET(12, 17)
+			>;
+	};
+};
-- 
2.25.1