Re: Thinkpad T20: DMA and power management

On 10/16/06, Michael Karcher <[email protected]> wrote:
> Hello,
>
> With a Thinkpad T20 after applying the fix I posted in
> https://bugs.freedesktop.org/show_bug.cgi?id=8662 I noticed following
> problems with vertex DMA enabled: Vertex DMA hangs (i.e. no triangle is
> painted at all, 3D engine hangs, tested using a simple handmade program
> that sends a draw-request for the front-buffer to the DRM) after the
> processor entering C3 state or after an suspend-to-ram/resume cycle
> (with vanilla 2.6.18 ACPI), independant of C3 usage. The settings used
> are "DmaType AGP", "BusType AGP", "AGPMode 2", "ShadowStatus Off".
>
> This looks like a bus mastering problem, especially the C3 state problem
> (vertex dma works like a charm with max_cstate=2), but lspci -H1 -vv
> still shows the master bit on the graphics card set. Any further ideas
> how to track this bug down?
>
> Furthermore, the problem disappears (incurring a performance drop from
> 380 fps (AGP/VDMA) to 300 fps for gears, standard window size, 16bpp)
> when using PCI DMA instead of AGP DMA. (The 300 fps for PCI are
> independent of vertex DMA enabled or disabled. AGP with vertex DMA
> disabled is also 300 fps), so it might be an agpgart problem (this
> computer uses the Intel 440BX chipset and thus the intel_agp driver)

This is a known problem.  AGP is not properly re-initalized after
resume.  the work around at the moment is to use PCI DMA.  There was
some discussion about this a couple years ago on one of the DRI lists.

Alex

>
> Michael Karcher
>

-------------------------------------------------------------------------
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done quickly with pre-integrated technology to make your job easier
Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642
--