From d52fea5bede33818def6af692644e5de27bfc1b3 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ville=20Syrj=C3=A4l=C3=A4?= Date: Mon, 28 Apr 2014 15:44:57 +0300 Subject: [PATCH] drm/i915: Merge LP1+ watermarks in safer way MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit On ILK when we disable a particular watermark level, we must maintain the actual watermark values for that level for some time (until the next vblank possibly). Otherwise we risk underruns. In order to achieve that result we must merge the LP1+ watermarks a bit differently since we must also merge levels that are to be disabled. We must also make sure we don't overflow the fields in the watermark registers in case the calculated watermarks come out too big to fit. As early as possbile we mark all computed watermark levels as disabled if they would exceed the register maximums. We make sure to leave the actual watermarks for such levels zeroed out. Then during merging, we take the maxium values for every level, regardless if they're disabled or not. That may seem a bit pointless since at the moment all the watermark levels we merge should have their values zeroed if the level is already disabled. However soon we will be dealing with intermediate watermarks that, in addition to the new watermark values, also contain the previous watermark values, and so levels that are disabled may no longer be zeroed out. v2: Split the patch in two (Paulo) Use if() instead of & when merging ->enable (Paulo) Signed-off-by: Ville Syrjälä Reviewed-by: Paulo Zanoni [danvet: Fix commit message as noted by Paulo.] Signed-off-by: Daniel Vetter --- Reading git-format-patch failed