Re: Problem: screen partially garbled in i830m (regression)

[Dave Airlie <airlied@linux.ie>]

> I sent this mail to David Airlie two weeks ago but I haven't gotten a
> reply so far, that's why I'm posting to LKML this time.  Short summary:
> 874808c6dd429f7431b906a32c7f78a68e7636af broke intel_agp.ko for me, I'm
> getting a garbled screen.

I'm travelling, and I'll try and get Zhenyu to take a look at what he 
changed.. but he is also travelling...

We probably need two defines..

Dave.

> --------------------------------
>
> Hello David,
>
> with recent kernels, there seems to be a problem with agpgart for my
> i830m chipset. The upper part of the screen is garbled, e.g. I can make
> out parts of the image that is to be displayed, but it's chopped and
> repeated. The box with which I'm having this problem is a not a regular
> PC, but a x86-based set top box called S100. It's got a fanless Celeron
> 733 MHz and 128M RAM and it's somewhat popular due to its cheapness.
> Just makes a nice living-room computer :)  I'll attach the output of
> lspci -vvv.
> FYI, I'm not using the official X.org driver but its IEGD counterpart.
> Unfortunately, the S100 comes with a TV-out encoder chip that's only
> supported by their closed source driver. Since the kernel is not tainted
> by that, it shouldn't be a problem - similar problems also occur with
> X.org drivers.
>
> With working kernels, I'd get the following messages in dmesg:
>
> <--snip-->
> [   40.188375] agpgart: Detected an Intel 830M Chipset.
> [   40.188741] agpgart: Detected 380K stolen memory.
> [   40.199908] agpgart: AGP aperture is 128M @ 0xf0000000
> <--snap-->
>
> A broken kernel will result in the following messages:
>
> <--snip-->
> Jul 25 16:29:42 mythbuntu-alpha2 kernel: [   44.941473] Linux agpgart
> interface v0.102 (c) Dave Jones
> Jul 25 16:29:42 mythbuntu-alpha2 kernel: [   44.957021] agpgart:
> Detected an Intel 830M Chipset.
> Jul 25 16:29:42 mythbuntu-alpha2 kernel: [   44.957605] agpgart: No
> pre-allocated video memory detected.
> Jul 25 16:29:42 mythbuntu-alpha2 kernel: [   44.968696] agpgart: AGP
> aperture is 128M @ 0xf0000000
> <--snap-->
>
> I used git-bisect to narrow down change that introduced this problem and
> came up with this:
>
> <--snip-->
>
> 874808c6dd429f7431b906a32c7f78a68e7636af is first bad commit
> commit 874808c6dd429f7431b906a32c7f78a68e7636af
> Author: Wang Zhenyu <zhenyu.z.wang@intel.com>
> Date:   Wed Jun 6 11:16:25 2007 +0800
>
>  [AGPGART] intel_agp: Add support for G33, Q33 and Q35 chipsets
>
>  This patch adds pci ids for G33, Q33 and Q35 chips, and update with new
>  GTT size and stolen mem size detect method on these chips.
>
>  Signed-off-by: Wang Zhenyu <zhenyu.z.wang@intel.com>
>  Signed-off-by: Dave Jones <davej@redhat.com>
>
> :040000 040000 39b18b6860f139cb28a80020dc9347314753e16d
> da24fb8672087cdfe6509cd1d4cb189534f887d6 M  drivers
> <--snap-->
>
> Particulary, there's a change to agp.h:
>
> <--snip-->
> -#define I830_GMCH_GMS_MASK  0x70
> +#define I830_GMCH_GMS_MASK  0xF0
> <--snap-->
>
> I reverted this change in my git tree and I'm now running
> 2.6.23-rc3-gb377fd39-dirty without any distortion at all. Do you think
> this can be fixed? I'll be glad to provide more Information. Thank you
> for your time!
>
>
> Regards,
>
> Michael
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