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

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Message-Id: <869cc1b1-0836-a53b-31d7-9fec50d8cc52@linux.vnet.ibm.com>
Date:   Tue, 15 Aug 2017 18:02:57 -0400
From:   Ken Goldman <kgold@...ux.vnet.ibm.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     linux-ima-devel@...ts.sourceforge.net,
        linux-security-module@...r.kernel.org,
        tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send() performance by
 ignoring burstcount

On 8/13/2017 7:53 PM, msuchanek wrote:
> About 500 out of 700 mainboards sold today has a PS/2 port which is
> probably due to prevalence of legacy devices and usbhid limitations.
> 
> Similarily many boards have serial and parallel hardware ports.
> 
> In all diagrams detailed enough to show these ports I have seen them
> attached to the LPC bus.

Do these boards have a TPM?  Remember that the TPM requires special LPC 
bus cycles.

Even if so, the TPM LPC bus wait states are less than a usec.  My 
thought is that  it's unlikely that any device (serial port, mouse, 
keyboard, printer) will be adversely affected.