From f67476589afc9a4a48bc342f1b5f505b508bd1ff Mon Sep 17 00:00:00 2001 From: Prashant Laddha Date: Wed, 22 Apr 2015 14:32:34 -0300 Subject: [PATCH] [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 for validating with standards and suggestions on equations. Cc: Martin Bugge Signed-off-by: Prashant Laddha Signed-off-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab --- drivers/media/v4l2-core/v4l2-dv-timings.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/media/v4l2-core/v4l2-dv-timings.c b/drivers/media/v4l2-core/v4l2-dv-timings.c index c0e96382feba..32aa25fa560b 100644 --- a/drivers/media/v4l2-core/v4l2-dv-timings.c +++ b/drivers/media/v4l2-core/v4l2-dv-timings.c @@ -368,14 +368,14 @@ 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; @@ -529,7 +529,8 @@ 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; image_height = (frame_height - v_fp - vsync - v_bp + 1) & ~0x1; if (aspect.numerator == 0 || aspect.denominator == 0) {