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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

  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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