linux-kernel - Re: [PATCH v2 15/18] drivers/fsi: Add documentation for GPIO based FSI master

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Message-ID: <f0933f56-6a23-9c53-6e10-0e1ca18082e2@ozlabs.org>
Date:   Thu, 19 Jan 2017 10:11:16 +0800
From:   Jeremy Kerr <jk@...abs.org>
To:     Rob Herring <robh@...nel.org>, christopher.lee.bostic@...il.com
Cc:     mark.rutland@....com, linux@...linux.org.uk,
        gregkh@...uxfoundation.org, mturquette@...libre.com,
        geert+renesas@...der.be, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, joel@....id.au,
        linux-kernel@...r.kernel.org, andrew@...id.au,
        alistair@...ple.id.au, benh@...nel.crashing.org,
        Chris Bostic <cbostic@...ibm.com>
Subject: Re: [PATCH v2 15/18] drivers/fsi: Add documentation for GPIO based
 FSI master

Hi Chris,

>From this:

>> +
>> +The standard FSI master node
>> +----------------------------
>> +This node describes a FSI master implmemented fully in hardware
>> +with dedicated input/output pins required for its function (i.e.
>> +not using generic GPIO pins).
>> +Required property:
>> +	compatible = "ibm,fsi-master"

and this:

>> +Example:
>> +
>> +fsi-master {
>> +	compatible = "ibm,fsi-master-gpio", "ibm,fsi-master";
> 
> From the description, these should be mutually exclusive.

I agree with Rob here. The intention is for "ibm,fsi-master" to be an
abstract master -- simply indicating that this node describes a master,
with no specific implementation, and "ibm,fsi-master-gpio" to be a
GPIO-based implementation. A hardware-based FSI master would have a
different compatible value, based on the hardware.

We should remove references to implementations in the "The standard FSI
master node" section, because this is independent of implementation.

>> +	clk-gpios = <&gpio 0>, <&gpio 6>;
>> +	data-gpios = <&gpio 1>, <&gpio 7>;
>> +	enable-gpios = <&gpio 2>, <&gpio 8>;
>> +	trans-gpios = <&gpio 3>, <&gpio 9>;
>> +	mux-gpios = <&gpio 4>, <&gpio 10>;

Do we support multiple-link masters? This example implies a 2-link
master.

Cheers,


Jeremy