linux-kernel - Re: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send() performance by ignoring burstcount

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Message-Id: <1502712773.6179.26.camel@linux.vnet.ibm.com>
Date:   Mon, 14 Aug 2017 08:12:53 -0400
From:   Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     Peter Huewe <PeterHuewe@....de>,
        Ken Goldman <kgold@...ux.vnet.ibm.com>,
        linux-ima-devel@...ts.sourceforge.net,
        linux-security-module@...r.kernel.org,
        tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send()
 performance by ignoring burstcount

On Mon, 2017-08-14 at 13:56 +0300, Jarkko Sakkinen wrote:

> > > Since the main concern about this change is breaking old systems that
> > > might potentially have other peripherals hanging off the LPC bus, can
> > > we define a new Kconfig option, with the default as 'N'?
> > > 
> > > Mimi
> > 
> > I guess that could make sense but I would like to hear feedback first.
> > 
> > /Jarkko
> 
> And I'm worried would that it'd be left for many years to come as an
> option.  I do not have any metrics what portion of hardware in the field
> would break if this is turned on.
> 
> It would slow down kernel testing as I would have to run tests for the
> driver with that option turned on and off because it is a major shift
> from how driver functions. And I have zero idea how long I would go on
> doing this.
> 
> One maybe a little bit better option would be to have a sysfs attribute
> for this functionality (disable_burst_count). What do you think about
> that?

That works!  So we'll define a module_param named disable_burst_count,
which can be specified on the boot command line.

Mimi