linux-kernel - Re: [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support

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Message-ID: <1480503686.9183.69.camel@pengutronix.de>
Date:   Wed, 30 Nov 2016 12:01:26 +0100
From:   Jan Lübbe <jlu@...gutronix.de>
To:     Grygorii Strashko <grygorii.strashko@...com>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Mugunthan V N <mugunthanvnm@...com>,
        Richard Cochran <richardcochran@...il.com>,
        Sekhar Nori <nsekhar@...com>, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        devicetree@...r.kernel.org, Murali Karicheri <m-karicheri2@...com>,
        Wingman Kwok <w-kwok2@...com>
Subject: Re: [PATCH 4/6] net: ethernet: ti: cpts: add ptp pps support

On Mo, 2016-11-28 at 17:04 -0600, Grygorii Strashko wrote:
> --- a/Documentation/devicetree/bindings/net/keystone-netcp.txt
> +++ b/Documentation/devicetree/bindings/net/keystone-netcp.txt
> @@ -127,6 +127,16 @@ Optional properties:
>                 The number of external time stamp channels.
>                 The different CPTS versions might support up 8
>                 external time stamp channels. if absent - unsupported.
> +       - cpts-ts-comp-length:
> +               Enable time stamp comparison event and TS_COMP signal output
> +               generation when CPTS counter reaches a value written to
> +               the TS_COMP_VAL register.
> +               The generated pulse width is 3 refclk cycles if this property
> +               has no value (empty) or, otherwise, it should specify desired
> +               pulse width in number of refclk periods - max value 2^16.
> +               TS_COMP functionality will be disabled if not present.
> +       - cpts-ts-comp-polarity-low:
> +               Set polarity of TS_COMP signal to low. Default is hight.

Why is this configured via DT? Are the values fixed for a given board,
depending on external components? Couldn't this be configured somewhere
else?

Regards,
Jan
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