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

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Following up on this thread based on this week's TCG call ...

1 - burstCount can safely be ignored on writes.  This is explicit in
most places in the TCG spec.  In places where it is not explicit, it was 
simply an editorial omission.  We are going through the spec and adding 
"without incurring wait states."

TCG is willing to publish an errata if that makes developers more 
comfortable.

2 - These are multi-mhz buses.  The TPM vendors conformed that wait 
states, even if incurred, will be sub-usec.  I.e., less that a microsecond.

Essentially, the DD is loading the FIFO, and the TPM is unloading the 
FIFO at processor speeds.

Thus, even if one were worried about an odd system new enough to have a 
TPM, but old enough to have an LPC attached printer, keyboard, mouse or 
floppy, the delay in printing or typing will be insignificant.

3 - I asked several platform vendors with long TCG experience, and they 
said that they know of no motherboards that share the LPC bus with a TPM 
plus another device.

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Thread

[PATCH] tpm: improve tpm_tis send() performance by ignoring burstcount Nayna Jain <nayna@linux.vnet.ibm.com> - 2017-08-07 13:50 +0200
  Re: [PATCH] tpm: improve tpm_tis send() performance by ignoring burstcount Peter Huewe <peterhuewe@gmx.de> - 2017-08-07 14:00 +0200
    Re: [PATCH] tpm: improve tpm_tis send() performance by ignoring  burstcount Nayna <nayna@linux.vnet.ibm.com> - 2017-08-07 16:30 +0200
      Re: [PATCH] tpm: improve tpm_tis send() performance by ignoring  burstcount Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2017-08-09 00:00 +0200
    Re: [PATCH] tpm: improve tpm_tis send() performance by ignoring  burstcount Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2017-08-08 21:20 +0200
      Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send() performance by  ignoring burstcount Ken Goldman <kgold@linux.vnet.ibm.com> - 2017-08-09 22:30 +0200
        Aw: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send()  performance by ignoring burstcount "Peter Huewe" <PeterHuewe@gmx.de> - 2017-08-09 22:50 +0200
          Re: Aw: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send()  performance by ignoring burstcount Ken Goldman <kgold@linux.vnet.ibm.com> - 2017-08-12 00:00 +0200
            Re: Aw: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send()  performance by ignoring burstcount Ken Goldman <kgold@linux.vnet.ibm.com> - 2017-08-16 22:00 +0200
      Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send() performance by  ignoring burstcount Ken Goldman <kgold@linux.vnet.ibm.com> - 2017-08-09 22:30 +0200
        Aw: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send()  performance by ignoring burstcount "Peter Huewe" <PeterHuewe@gmx.de> - 2017-08-09 23:10 +0200
          Re: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send()  performance by ignoring burstcount Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2017-08-11 13:20 +0200
            Re: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send()  performance by ignoring burstcount Mimi Zohar <zohar@linux.vnet.ibm.com> - 2017-08-11 17:40 +0200
              Re: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send()  performance by ignoring burstcount Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2017-08-14 13:00 +0200
                Re: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send()  performance by ignoring burstcount Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2017-08-14 13:00 +0200
                Re: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send()  performance by ignoring burstcount Mimi Zohar <zohar@linux.vnet.ibm.com> - 2017-08-14 14:10 +0200
                Re: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send()  performance by ignoring burstcount Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2017-08-15 08:10 +0200
                Re: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send()  performance by ignoring burstcount Mimi Zohar <zohar@linux.vnet.ibm.com> - 2017-08-14 14:20 +0200
                Re: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send()  performance by ignoring burstcount Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2017-08-15 08:10 +0200
          Re: Aw: Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send()  performance by ignoring burstcount Ken Goldman <kgold@linux.vnet.ibm.com> - 2017-08-11 23:40 +0200
            Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send() performance  by ignoring burstcount msuchanek <msuchanek@suse.de> - 2017-08-14 02:00 +0200
              Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send() performance by  ignoring burstcount Ken Goldman <kgold@linux.vnet.ibm.com> - 2017-08-16 00:10 +0200
                Re: [tpmdd-devel] [PATCH] tpm: improve tpm_tis send() performance  by ignoring burstcount Michal Suchánek <msuchanek@suse.de> - 2017-08-16 12:30 +0200
        Re: [Linux-ima-devel] [tpmdd-devel] [PATCH] tpm: improve tpm_tis  send() performance by ignoring burstcount Ken Goldman <kgold@linux.vnet.ibm.com> - 2017-08-11 23:50 +0200
  Re: [PATCH] tpm: improve tpm_tis send() performance by ignoring  burstcount Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> - 2017-08-08 21:10 +0200

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