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

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Date:   Thu, 11 May 2017 11:14:13 -0500
From:   Christopher Bostic <cbostic@...ux.vnet.ibm.com>
To:     Jeremy Kerr <jk@...abs.org>, 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



On 5/10/17 8:58 PM, Jeremy Kerr wrote:
> 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.

Hi Jeremy,

Understand now -will make the change.

Thanks
-Chris

> Cheers,
>
>
> Jeremy
>