From: Jesse Barnes Date: Tue, 22 Sep 2015 19:15:54 +0000 (-0700) Subject: drm/i915: workaround bad DSL readout v3 X-Git-Tag: omap-for-v4.3/fixes-rc5~94^2^2~2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=41b578fb0e8b930f2470d3f673b0fa279e77a7b8;p=pandora-kernel.git drm/i915: workaround bad DSL readout v3 On HSW at least (still testing other platforms, but should be harmless elsewhere), the DSL reg reads back as 0 when read around vblank start time. This ends up confusing the atomic start/end checking code, since it causes the update to appear as if it crossed a frame count boundary. Avoid the problem by making sure we don't return scanline_offset from the get_crtc_scanline function. In moving the code there, I add to add an additional delay since it could be called and have a legitimate 0 result for some time (depending on the pixel clock). v2: move hsw dsl read hack to get_crtc_scanline (Ville) v3: use break instead of goto (Ville) update comment with workaround details (Ville) References: https://bugs.freedesktop.org/show_bug.cgi?id=91579 Signed-off-by: Jesse Barnes Reviewed-by: Ville Syrjälä Signed-off-by: Jani Nikula --- Reading git-diff-tree failed