On Mon, Jan 2, 2012 at 5:07 PM, Helge Deller deller@gmx.de wrote:
I'm facing the problem with the radeon drm driver, that I now manually need to set the kernel module parameter radeon.no_wb to 1 at bootup, else X just hangs in average up to 8 seconds per minute without any real activity (X or the video driver just seems to wait for something..).
Fedora 13 (kernel 2.6.34.9-69.fc13.x86_64) worked without problems, while all following Fedora distributions including F16 have this problem. I'm using a dual-DVI ATI RV280 [FireMV 2200 PCI].
I did compared the sources of those kernels and the only obvious change to me is in radeon_ring.c: radeon_ring_free_size() where those lines were added at the top of the function: if (rdev->wb.enabled) rdev->cp.rptr = le32_to_cpu(rdev->wb.wb[RADEON_WB_CP_RPTR_OFFSET/4]);
Given the problems I'm seeing (X-Windows hangs for a few seconds every time) this fits with the idea, that the driver is waiting for a free slot but can't find any (maybe due to wrong values returned by not-working WB?).
I'm wondering, if "rdev->wb.enabled" is correct in this place and if "dev_priv->writeback_works" shouldn't be used instead here?
It's possible that writeback doesn't work on your system in which case no_wb=1 is apprioriate. dev_priv->writeback_works is part of the old UMS drm and is not used by KMS. The KMS code does not test if writeback works prior to enabling it like UMS did. The slow down you are seeing is caused by the driver waiting for the fence to be written back to memory. If writeback does not work, the fence is never written by the hw and the driver has to wait for the fence to time out.
Alex
Helge
dri-devel mailing list dri-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/dri-devel