From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5979FC2BB1D for ; Fri, 17 Apr 2020 23:54:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 33BA920732 for ; Fri, 17 Apr 2020 23:54:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726039AbgDQXyL (ORCPT ); Fri, 17 Apr 2020 19:54:11 -0400 Received: from mga02.intel.com ([134.134.136.20]:50305 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726036AbgDQXyK (ORCPT ); Fri, 17 Apr 2020 19:54:10 -0400 IronPort-SDR: 7eg1eFXc2vRZb9fVFcA3WPj2xnXTtYzawBpJ+DsWNtFunL5D5rg5wQSAJxbHd9dznqbZ5QgleG RPlQO5rk0aCg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Apr 2020 16:54:10 -0700 IronPort-SDR: INuBFc2w3pz1Qnx5q0H2bPrsBKKuM+AC451BL0AlRdoaaznmYMNU5uQiAaQTu3ys2Gj1t/n2Tj 3iSKNTvcAt3A== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,395,1580803200"; d="scan'208";a="244840451" Received: from zhiwang1-mobl5.ger.corp.intel.com (HELO localhost) ([10.252.42.90]) by fmsmga007.fm.intel.com with ESMTP; 17 Apr 2020 16:54:07 -0700 Date: Sat, 18 Apr 2020 02:54:06 +0300 From: Jarkko Sakkinen To: Omar Sandoval Cc: Peter Huewe , Jason Gunthorpe , linux-integrity@vger.kernel.org Subject: Re: [PATCH] tpm_tis: work around status register bug in STMicroelectronics TPM Message-ID: <20200417235406.GA85230@linux.intel.com> References: <6c55d7c1fb84e5bf2ace9f05ec816ef67bd873e1.1586990595.git.osandov@fb.com> <20200416170810.GD199110@linux.intel.com> <20200416185433.GA701157@vader> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200416185433.GA701157@vader> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On Thu, Apr 16, 2020 at 11:54:33AM -0700, Omar Sandoval wrote: > On Thu, Apr 16, 2020 at 08:08:10PM +0300, Jarkko Sakkinen wrote: > > On Wed, Apr 15, 2020 at 03:45:22PM -0700, Omar Sandoval wrote: > > > From: Omar Sandoval > > > > > > We've encountered a particular model of STMicroelectronics TPM that > > > transiently returns a bad value in the status register. This causes the > > > kernel to believe that the TPM is ready to receive a command when it > > > actually isn't, which in turn causes the send to time out in > > > get_burstcount(). In testing, reading the status register one extra time > > > convinces the TPM to return a valid value. > > > > > > Signed-off-by: Omar Sandoval > > > > So what is the bad value? > > 0xff. Sorry, I thought it would be clear from the code and comment in > the patch itself. Would you prefer for me to repeat it in the commit > message? It is part of the problem description where as "bad value" does not have any particular meaning. /Jarkko