[media] v4l2-dv-timings: fix rounding error in vsync_bp calculation
authorPrashant Laddha <prladdha@cisco.com>
Wed, 22 Apr 2015 17:32:34 +0000 (14:32 -0300)
committerMauro Carvalho Chehab <mchehab@osg.samsung.com>
Fri, 1 May 2015 10:14:02 +0000 (07:14 -0300)
commitf67476589afc9a4a48bc342f1b5f505b508bd1ff
treedc402509bceed35ddf256a3dbda258d7702faf8e
parentef403bcaf16b704b772cf33cc2871fb8693d3bb3
[media] v4l2-dv-timings: fix rounding error in vsync_bp calculation

Changed the rounding offsets used in vsync_bp calculation in cvt and
gtf timings. The results for vsync_bp should now match with results
from timing generator spreadsheets for cvt and gtf standards.

In the vsync_bp calculation for cvt, always round down the value of
(CVT_MIN_VSYNC_BP / h_period_est) and then add 1. It thus, reflects
the equation used in timing generator spreadsheet. Using 1999999 as
rounding offset, could pontentially lead to bumping up the vsync_bp
value by extra 1.

In the vsync_bp calculations for gtf, instead of round up or round
down, round the (CVT_MIN_VSYNC_BP / h_period_est) to the nearest
integer.

Thanks to Martin Bugge <marbugge@cisco.com> for validating with
standards and suggestions on equations.

Cc: Martin Bugge <marbugge@cisco.com>
Signed-off-by: Prashant Laddha <prladdha@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
drivers/media/v4l2-core/v4l2-dv-timings.c