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Re: brcm4716 and PCIe

To: Hauke Mehrtens <hauke@hauke-m.de>
Subject: Re: brcm4716 and PCIe
From: Elliott Mitchell <ehem+outbound@m5p.com>
Date: Fri, 16 Nov 2012 12:17:05 -0800
Cc: "John W. Linville" <linville@tuxdriver.com>, "linux-mips@linux-mips.org" <linux-mips@linux-mips.org>, "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
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On Fri, Nov 16, 2012 at 06:13:56PM +0100, Hauke Mehrtens wrote:
> On 11/16/2012 05:44 AM, Elliott Mitchell wrote:
> > I happened to be browsing the linux-mips git repository and noticed the
> > commit at Tue, 10 Jul 2012 16:16:47.
> 
> What commit are you talking about? Do you have a commit id?

Looking at: 
http://git.linux-mips.org/?p=ralf/linux.git;a=commitdiff;h=1dfef20a4cf82997d4c7520138ed8188a181241c

I'm guessing "1dfef20a4cf82997d4c7520138ed8188a181241c" is the commit id.

Subject is: "brcmsmac: remove PCI_FORCEHT() macro"

Description is:
The BCM4716 is a SoC and does not have a PCI client interface, so this
condition is never true.

Acked-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

I'm guessing the piece of code is invoked on all flavors of bcm471[678],
so while it doesn't get invoked on most devices, some of them it
definitely can be.


> > The Broadcom 4716 *does* have an external PCI Express interface! Take a
> > look at the images on http://wiki.openwrt.org/toh/asus/rt-n16  If you
> > look at the image of the underside
> > (http://wiki.openwrt.org/_media/inbox/rt-n16_back_hires.jpg) on the right
> > side, CON3 and CON5 are the solder pads for mounting a mini-PCIe
> > connector and bracket.  Apparently V11 is a voltage regulator needed for
> > that to work, but on this an example of a Broadcom 4716 board that really
> > does allow a useable PCIe interface (with some hardware hacking).
> 
> Are you sure the Asus rt-n16 has a BCM4716 and not an BCM4718? Both have
> the same chip id (0x4716), but a different revision number (BCM4716 =
> rev 8, BCM4718 = rev 10). The BCM4716 and BCM4717 do not have a PCIe
> controller, just the BCM4718 has one [0].

I'm not actually.  Currently exploring a device with ASUS's minimal shell
they give you.  According to /proc/cpuinfo, "system type: Broadcom
BCM4716 chip rev 1 pkg 10".  If I'm looking at the correct byte in
/sys/devices/[...]/config, it does in fact appear to be 0x0A (decimal
10).

I've seen photos of some people in Taiwan who soldered something at V11
(presumably a voltage regulator, it's all Chinese to me).  I'm guessing
they did in fact get a MiniPCIe card to work, but everything is in the
wrong language.   :-)   The crucial build photo of the regulator module
has disappeared, so it is more difficult to reconstruct.


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