From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from bgl-iport-1.cisco.com ([72.163.197.25]:59675 "EHLO bgl-iport-1.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753089AbbDHNUa (ORCPT ); Wed, 8 Apr 2015 09:20:30 -0400 From: Prashant Laddha To: linux-media@vger.kernel.org Cc: Hans Verkuil , Martin Bugge , Prashant Laddha Subject: [PATCH 1/2] v4l2-dv-timings: fix rounding error in vsync_bp calculation Date: Wed, 8 Apr 2015 18:39:28 +0530 Message-Id: <1428498569-6751-2-git-send-email-prladdha@cisco.com> In-Reply-To: <1428498569-6751-1-git-send-email-prladdha@cisco.com> References: <1428498569-6751-1-git-send-email-prladdha@cisco.com> Sender: linux-media-owner@vger.kernel.org List-ID: 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. Cc: Hans Verkuil Cc: Martin Bugge Thanks to Martin Bugge for validating with standards and suggestions on equations. Signed-off-by: Prashant Laddha --- drivers/media/v4l2-core/v4l2-dv-timings.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/media/v4l2-core/v4l2-dv-timings.c b/drivers/media/v4l2-core/v4l2-dv-timings.c index 80e4722..5e114ee 100644 --- a/drivers/media/v4l2-core/v4l2-dv-timings.c +++ b/drivers/media/v4l2-core/v4l2-dv-timings.c @@ -367,14 +367,14 @@ bool v4l2_detect_cvt(unsigned frame_height, unsigned hfreq, unsigned vsync, /* Vertical */ if (reduced_blanking) { v_fp = CVT_RB_V_FPORCH; - v_bp = (CVT_RB_MIN_V_BLANK * hfreq + 1999999) / 1000000; + v_bp = (CVT_RB_MIN_V_BLANK * hfreq) / 1000000 + 1; v_bp -= vsync + v_fp; if (v_bp < CVT_RB_MIN_V_BPORCH) v_bp = CVT_RB_MIN_V_BPORCH; } else { v_fp = CVT_MIN_V_PORCH_RND; - v_bp = (CVT_MIN_VSYNC_BP * hfreq + 1999999) / 1000000 - vsync; + v_bp = (CVT_MIN_VSYNC_BP * hfreq) / 1000000 + 1 - vsync; if (v_bp < CVT_MIN_V_BPORCH) v_bp = CVT_MIN_V_BPORCH; @@ -543,7 +543,7 @@ bool v4l2_detect_gtf(unsigned frame_height, /* Vertical */ v_fp = GTF_V_FP; - v_bp = (GTF_MIN_VSYNC_BP * hfreq + 999999) / 1000000 - vsync; + v_bp = (GTF_MIN_VSYNC_BP * hfreq + 500000) / 1000000 - vsync; if (scan == V4L2_DV_INTERLACED) image_height = (frame_height - 2 * v_fp - 2 * vsync - 2 * v_bp) -- 1.9.1