From: Ville Syrjälä Date: Wed, 12 Jun 2013 19:11:18 +0000 (+0300) Subject: drm/i915: Try harder to disable trickle feed on VLV X-Git-Tag: v3.11-rc1~65^2~61^2~14 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e0d8d59b0831523da61739c9d5e3bc3c77d7b5db;p=pandora-kernel.git drm/i915: Try harder to disable trickle feed on VLV The specs are a bit unclear whether the per-plane trickle feed disable control exists on VLV. There is another trickle feed disable control in the MI_ARB register. After some experimentation it turns out both the DSPCNTR trickle feed bits and the MI_ARB bit can be toggled. However the DSPCNTR bits don't seem to have any effect. The MI_ARB bit, on the other hand, has a noticable effect. I performed an experiment where I reduced the FIFO size via DSPARB and observed the effect of the MI_ARB trickle feed bit on the display. Using a 1920x1080-60 mode, with MI_ARB=0x4 the display started to have problems with DSPARB=0x42424242, whereas with MI_ARB=0x0 the problems didn't start until DSPARB=0x09090909. This seems to confirm that the MI_ARB trickle feed bit actually does work. So replace the use of the DSPCNTR trickle feed bits with MI_ARB on VLV. v2: Amend commit message with results from experimentation Signed-off-by: Ville Syrjälä Reviewed-by: Jesse Barnes Signed-off-by: Daniel Vetter --- Reading git-diff-tree failed