linux-kernel - Re: [PATCH v4 19/23] drivers/fsi: Add GPIO based FSI master

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Date:   Mon, 10 Apr 2017 07:55:37 +1000
From:   Benjamin Herrenschmidt <benh@....ibm.com>
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@...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>,
        "Edward A . James" <eajames@...ibm.com>,
        Jeremy Kerr <jk@...abs.org>
Subject: Re: [PATCH v4 19/23] drivers/fsi: Add GPIO based FSI master

On Mon, 2017-04-10 at 07:53 +1000, Benjamin Herrenschmidt wrote:
> FYI. pdbg in userspace operates without any  delays in practice, the
> overhead between the various load/store instructions seems
> sufficient.
> 
> The only delay that's needed is when going through the FSI2PIB (to do
> SCOMs) where it seems like back-2-back accesses can be problematic.

Note: This isn't an objection to merging the patches. We can look at
doing an improved backend later.

Cheers,
Ben.