From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Sakkinen Subject: Re: tpm: read burstcount from TPM_STS in one 32-bit transaction Date: Tue, 1 Aug 2017 16:31:45 +0300 Message-ID: <20170801133145.mqfen3bskzwwabwp@linux.intel.com> References: <20170725150443.7cf8fc91@kitsune.suse.cz> <1501004171.3689.25.camel@linux.vnet.ibm.com> <20170725201758.230de968@kitsune.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: <20170725201758.230de968-6hIufAJW0g4CVLCxKZUutA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: tpmdd-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Michal =?iso-8859-1?Q?Such=E1nek?= Cc: Christophe Ricard , tpmdd-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: tpmdd-devel@lists.sourceforge.net On Tue, Jul 25, 2017 at 08:17:58PM +0200, Michal Such=E1nek wrote: > On Tue, 25 Jul 2017 10:36:11 -0700 > James Bottomley wrote: > = > > On Tue, 2017-07-25 at 15:04 +0200, Michal Such=E1nek wrote: > > > Hello, > > > = > > > in commit 9754d45e9970 ("tpm: read burstcount from TPM_STS in one > > > 32-bit transaction") you change reading of two 8-bit values to one > > > 32bit read. This is obviously wrong wrt endianess unless the > > > underlying tpm_tis_read32 does endian conversion.=A0 = > > = > > Some of the bus read primitives do do endianness conversions. =A0The > > problem is with the SPI attachment, which has unclear endianness. =A0A > > standard PCI bus attachment uses ioread32() which automatically > > transforms from a little endian bus to the cpu endianness, however SPI > > is forced to transfer the bytes one at a time over the serial bus and > > then transform. =A0The assumption seems to be that the TIS TPM is > > replying in little endian format when SPI connected. > > = > = > Yes, that makes sense. > = > Thanks for clarification. > = > Michal Thank you for reporting this and thanks James for explaining this. I do not have access to PPC hardware with SPI-TPM. /Jarkko ---------------------------------------------------------------------------= --- Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot