linux-kernel - Re: SDVO on E6xx

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Date:	Wed, 21 Nov 2012 17:38:08 +0100
From:	roman@...ek.net
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	linux-kernel@...r.kernel.org, patrik.r.jakobsson@...il.com,
	christian.gmeiner@...il.com
Subject: Re: SDVO on E6xx

Hi Alan,

> There is an Intel driver with open kernel code and proprietary userspace for
> the Imagination 3D engine (EMGD) although only for an out of maintenance
> Fedora and for Meego and in both cases for ancient kernels.

I knew about EMGD, but not that there's code available for parts of it.

> The fully open driver is built by extracting the relevant information and
> code from these releases.

Ah, ok. Then I'll try to extract even a bit more ;-) Thanks very much for that
hint!

> If you unpack that it contains a tar ball which you can unpack which
> contains the driver.
>
> emgd/pal/sdvo
>
> looks kind of promising.

Got it now (it's common/drm/emgd_drm.tgz). 

I started to look around there, and emgd/display/pi/tnc/i2c_gmbus_tnc.c looks
as a good source of infos. At least it mentions E6xx quite often, and it uses
functions read/write_mmio_reg_tnc on TunnelCreek.

>From there I got to an interesting comment:

#ifdef CONFIG_TNC
/* Based on display port determine which mmio base to use:
 *       port_type == SDVO ==> use 0:3:0 device mmio
 *       port_type == LVDS ==> use 0:2:0 device mmio
 *       port_type == LPC  ==> use 0:31:0 device mmio
 */

Indeed, I have those additional PCI devices, and the BARs of 0:03.0 look much
like those of 0:02.0. It has PCI ID 8086:8182 and class 0x0400
(multimedia/video). And in BAR 0 at offset 0x5100 there are values that look
more like GMBUS...
(0:1f.0 exists, it declares itself as ISA bridge, and it has no BARs
assigned.)

Ok, I'll go down that road, poke around a bit there, and we'll see how far I
can get!

Roman

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