From: "Shaikh, Azhar" <azhar.shaikh@intel.com>
To: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: "jarkko.sakkinen@linux.intel.com"
<jarkko.sakkinen@linux.intel.com>,
"jgunthorpe@obsidianresearch.com"
<jgunthorpe@obsidianresearch.com>,
"tpmdd-devel@lists.sourceforge.net"
<tpmdd-devel@lists.sourceforge.net>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-security-module@vger.kernel.org"
<linux-security-module@vger.kernel.org>
Subject: RE: [PATCH v3] tpm: Enable CLKRUN protocol for Braswell systems
Date: Thu, 8 Jun 2017 19:02:54 +0000 [thread overview]
Message-ID: <5FFFAD06ADE1CA4381B3F0F7C6AF5828910FA4@ORSMSX109.amr.corp.intel.com> (raw)
In-Reply-To: <20170608192259.43150ffa@lxorguk.ukuu.org.uk>
> -----Original Message-----
> From: Alan Cox [mailto:gnomes@lxorguk.ukuu.org.uk]
> Sent: Thursday, June 8, 2017 11:23 AM
> To: Shaikh, Azhar <azhar.shaikh@intel.com>
> Cc: jarkko.sakkinen@linux.intel.com; jgunthorpe@obsidianresearch.com;
> tpmdd-devel@lists.sourceforge.net; linux-kernel@vger.kernel.org; linux-
> security-module@vger.kernel.org
> Subject: Re: [PATCH v3] tpm: Enable CLKRUN protocol for Braswell systems
>
> > > > + outb(0x80, 0xCC);
> > > > +
> > > > + /* Make sure the above write is completed */
> > > > + wmb();
> > >
> > > Why the wmb(). It doesn't do what the comment says! Also this code
> > > is x86 specific
> > >
> > >
> >
> > Memory barrier to enforce the order so that the outb() is completed,
> which ensures that the LPC clocks are running before sending any TPM
> command.
>
> wmb() doesn't do that. It merely ensures that the write has been posted to
> the fabric. If as I suspect your LPC bus implements outb() as a non-posted
> write you don't need the wmb(). If it doesn't then you need to issue
> whatever access is needed to the fabric to ensure the post completed (eg for
> PCI if you do an MMIO write you must do an MMIO read from the same
> devfn).
>
> Secondly outb(0x80, 0xCC) doesn't write 0xCC to port 0x80. It writes 0x80 to
> port 0xCC !
>
Oops my bad! I got that reversed. Will change it.
> Alan
next prev parent reply other threads:[~2017-06-08 19:02 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-01 19:13 [PATCH] tpm: Enable CLKRUN protocol for Braswell systems Azhar Shaikh
2017-06-01 23:56 ` kbuild test robot
2017-06-02 2:04 ` [PATCH v2] " Azhar Shaikh
[not found] ` <1496369044-38234-1-git-send-email-azhar.shaikh-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-06-05 13:32 ` Jarkko Sakkinen
2017-06-05 18:42 ` Shaikh, Azhar
2017-06-06 17:13 ` Jarkko Sakkinen
2017-06-07 21:23 ` [PATCH v3] " Azhar Shaikh
2017-06-07 21:44 ` Alan Cox
2017-06-08 1:11 ` Shaikh, Azhar
2017-06-08 12:38 ` Jarkko Sakkinen
2017-06-08 18:22 ` Alan Cox
2017-06-08 18:39 ` Jason Gunthorpe
2017-06-08 18:50 ` Alan Cox
2017-06-08 19:27 ` Shaikh, Azhar
2017-06-10 11:06 ` Jarkko Sakkinen
2017-06-08 19:02 ` Shaikh, Azhar [this message]
2017-06-08 23:46 ` [PATCH v4] " Azhar Shaikh
2017-06-10 11:13 ` Jarkko Sakkinen
2017-06-10 16:35 ` Shaikh, Azhar
2017-06-12 7:50 ` Jarkko Sakkinen
2017-06-14 0:51 ` Shaikh, Azhar
2017-06-14 14:46 ` Jarkko Sakkinen
2017-06-14 17:17 ` Shaikh, Azhar
2017-06-14 19:39 ` Azhar Shaikh
2017-06-18 23:52 ` Jarkko Sakkinen
[not found] ` <1497829956.2552.10.camel-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-06-19 2:12 ` Shaikh, Azhar
2017-06-19 2:17 ` [PATCH v5] " Azhar Shaikh
2017-06-19 14:51 ` Jarkko Sakkinen
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