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

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Message-ID: <6ae650c9-d68d-d2fc-8319-b7784cd2a749@kernel.org>
Date:   Fri, 13 Jan 2023 12:18:37 +0200
From:   Roger Quadros <rogerq@...nel.org>
To:     Siddharth Vadapalli <s-vadapalli@...com>, 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, nsekhar@...com
Cc:     netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        srk@...com
Subject: Re: [PATCH net-next 5/5] arm64: dts: ti: k3-am625-sk: Add cpsw3g cpts
 PPS support

Hi,

On 11/01/2023 13:44, Siddharth Vadapalli wrote:
> 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).

You mean there is no HWx_TX_PUSH0 pin? so user needs to use 0 for HWx_TX_PUSH1 pin?

Can you please define macros for HWx_TS_PUSH and GENFy so we avoid
human error with this different indexing methods?

DT should contain the name exactly in hardware.

So if pin is called HWx_TX_PUSH1 in hardware then DT should contain HWx_TX_PUSH(1).

> 
> 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)

Should this go in ./include/dt-bindings/pinctrl/k3.h ?
That way every board DT file doesn't have to define it.

The name should be made more platform specific.
e.g. K3_TS_OFFSET if it is the same for all K3 platforms.
If not then please add Platform name instead of K3.

> +
> +&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)
> +			>;
> +	};
> +};

cheers,
-roger