Message-ID: <1491344360.4166.68.camel@kernel.crashing.org>
Subject: Re: [PATCH v4 19/23] drivers/fsi: Add GPIO based FSI master
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Christopher Bostic <cbostic@linux.vnet.ibm.com>,
        Joel Stanley <joel@jms.id.au>
Cc: Rob Herring <robh+dt@kernel.org>, Mark Rutland <mark.rutland@arm.com>,
        Russell King <linux@armlinux.org.uk>, rostedt@goodmis.org,
        mingo@redhat.com, Greg KH <gregkh@linuxfoundation.org>,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andrew Jeffery <andrew@aj.id.au>,
        Alistair Popple <alistair@popple.id.au>,
        "Edward A . James" <eajames@us.ibm.com>, Jeremy Kerr <jk@ozlabs.org>
Date: Wed, 05 Apr 2017 08:19:20 +1000
In-Reply-To: <93b21624-11fc-b71b-aa78-6cb4371c87ae@linux.vnet.ibm.com>
References: <20170329174340.89109-1-cbostic@linux.vnet.ibm.com>
         <20170329174340.89109-20-cbostic@linux.vnet.ibm.com>
         <CACPK8XfOSYPidHF6=psC4mP-tkRyWTu0psdcK6EwA2E6FF53Uw@mail.gmail.com>
         <0e1bcf3a-e8d7-9f50-bdf7-2a1e7466665b@linux.vnet.ibm.com>
         <1490907014.3177.207.camel@kernel.crashing.org>
         <93b21624-11fc-b71b-aa78-6cb4371c87ae@linux.vnet.ibm.com>
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On Tue, 2017-04-04 at 12:32 -0500, Christopher Bostic wrote:
> Agreed that there is room for improvement.   I intend to look further 
> into your suggestions from here and our private conversation on the 
> matter and make changes as appropriate.  I have an open issue to track 
> this.  As it exists in this patch reads/writes from master to slave 
> fundamentally work.  

My understanding is they "seem to work if you get lucky with the timing
and fall apart under load". Or did I hear wrong ?

>  Given the pervasiveness and time to fully evaluate 
> and test any protocol updates I intend address this in the near future 
> with a separate follow on patch.

Please try the simple change I proposed in my email. It's a 4 or 5
lines change max to your clock_toggle function and how it's called in
send and receive. It should be trivial to check if things still "seem
to work" to begin with.

Do you have some kind of test mechanism that hammers the FSI
continuously ? Such as doing a series of putmemproc/getmemproc &
checking the values ?

Then you can run that while hammering the LPC bus and generally putting
the BMC under load and you'll quickly see if it's reliable or not.

Cheers,
Ben.