linux-kernel - Re: [PATCH v6 19/23] drivers/fsi: Add GPIO based FSI master

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Date:   Thu, 11 May 2017 09:58:16 +0800
From:   Jeremy Kerr <jk@...abs.org>
To:     Christopher Bostic <cbostic@...ux.vnet.ibm.com>,
        Joel Stanley <joel@....id.au>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>, rostedt@...dmis.org,
        mingo@...hat.com, Greg KH <gregkh@...uxfoundation.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Jeffery <andrew@...id.au>,
        Alistair Popple <alistair@...ple.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        "Edward A . James" <eajames@...ibm.com>
Subject: Re: [PATCH v6 19/23] drivers/fsi: Add GPIO based FSI master

Hi Chris,

> I don't think we'd want this per master.   The lock is for the 'top'
> master issuing commands.  Only the top master can initiate any
> transactions on the bus to any devices connected downstream. Downstream
> masters such as hub masters, etc... cannot initiate a command.

I think what Joel meant there was that we have it per *GPIO* master; if
there are two GPIO masters on a system, there's no need to provide
mutual exclusion to each (separate) set of GPIOs.

To implement this, we'd just move the lock into struct fsi_master_gpio.

Cheers,


Jeremy