[PATCH 0/2] rounding and overflow fix in cvt,gtf calculations

[PATCH 0/2] rounding and overflow fix in cvt,gtf calculations

[Prashant Laddha]

Hi,

Please find patches for rounding and overflow fixes in cvt,gtf
timings calculations in v4l2-utils. Similar fixes are posted for
v4l2-dv-timings recently.

Regards,
Prashant

Prashant Laddha (2):
  v4l2-ctl-modes: fix hblank, hsync rounding in gtf calculation
  v4l2-utils: fix overflow in cvt, gtf calculations

 utils/v4l2-ctl/v4l2-ctl-modes.cpp | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

-- 
1.9.1

[PATCH 1/2] v4l2-ctl-modes: fix hblank, hsync rounding in gtf calculation

[Prashant Laddha]

In gtf modeline calculations, currently hblank and hsync are rounded
down. hblank needs to be rounded to nearest multiple of twice the
cell granularity. hsync needs to be rounded to nearest multiple of
cell granularity. Changed the rounding calculation to match it with
the equations in standards.

Cc: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Prashant Laddha <prladdha@cisco.com>
---
 utils/v4l2-ctl/v4l2-ctl-modes.cpp | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/utils/v4l2-ctl/v4l2-ctl-modes.cpp b/utils/v4l2-ctl/v4l2-ctl-modes.cpp
index c775bda..4689006 100644
--- a/utils/v4l2-ctl/v4l2-ctl-modes.cpp
+++ b/utils/v4l2-ctl/v4l2-ctl-modes.cpp
@@ -457,12 +457,13 @@ bool calc_gtf_modeline(int image_width, int image_height,
 
 	h_blank = active_h_pixel * ideal_blank_duty_cycle /
 			 (100 * HV_FACTOR - ideal_blank_duty_cycle);
-	h_blank -= h_blank % (2 * GTF_CELL_GRAN);
+	h_blank = ((h_blank + GTF_CELL_GRAN) / (2 * GTF_CELL_GRAN))
+			  * (2 * GTF_CELL_GRAN);
 
 	total_h_pixel = active_h_pixel + h_blank;
 
-	h_sync  = (total_h_pixel * GTF_HSYNC_PERCENT) / 100;
-	h_sync -= h_sync % GTF_CELL_GRAN;
+	h_sync = (total_h_pixel * GTF_HSYNC_PERCENT) / 100;
+	h_sync = ((h_sync + GTF_CELL_GRAN / 2) / GTF_CELL_GRAN) * GTF_CELL_GRAN;
 
 	h_fp = h_blank / 2 - h_sync;
 	h_bp = h_fp + h_sync;
@@ -509,6 +510,5 @@ bool calc_gtf_modeline(int image_width, int image_height,
 		gtf->flags |= V4L2_DV_FL_REDUCED_BLANKING;
 	} else
 		gtf->polarities = V4L2_DV_VSYNC_POS_POL;
-
 	return true;
 }
-- 
1.9.1

[PATCH 2/2] v4l2-utils: fix overflow in cvt, gtf calculations

[Prashant Laddha]

Some of the intermediate calculations can exceed 32 bit signed range,
especially for higher resolutions and refresh rates. Type casting the
intermediate values to higher precision to avoid overflow.

Cc: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Prashant Laddha <prladdha@cisco.com>
---
 utils/v4l2-ctl/v4l2-ctl-modes.cpp | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/utils/v4l2-ctl/v4l2-ctl-modes.cpp b/utils/v4l2-ctl/v4l2-ctl-modes.cpp
index 4689006..072763a 100644
--- a/utils/v4l2-ctl/v4l2-ctl-modes.cpp
+++ b/utils/v4l2-ctl/v4l2-ctl-modes.cpp
@@ -216,7 +216,7 @@ bool calc_cvt_modeline(int image_width, int image_height,
 		if (ideal_blank_duty_cycle < 20 * HV_FACTOR)
 			ideal_blank_duty_cycle = 20 * HV_FACTOR;
 
-		h_blank = active_h_pixel * ideal_blank_duty_cycle /
+		h_blank = active_h_pixel * (long long)ideal_blank_duty_cycle /
 			 (100 * HV_FACTOR - ideal_blank_duty_cycle);
 		h_blank -= h_blank % (2 * CVT_CELL_GRAN);
 
@@ -430,7 +430,6 @@ bool calc_gtf_modeline(int image_width, int image_height,
 	tmp2 = active_v_lines + GTF_MIN_PORCH + interlace;
 
 	h_period_est = tmp1 / (tmp2 * v_refresh);
-
 	v_sync_bp = GTF_MIN_VSYNC_BP * HV_FACTOR * 100 / h_period_est;
 	v_sync_bp = (v_sync_bp + 50) / 100;
 
@@ -444,7 +443,7 @@ bool calc_gtf_modeline(int image_width, int image_height,
 	v_refresh_est = (HV_FACTOR * (long long)1000000) /
 			(h_period_est * total_v_lines / HV_FACTOR);
 
-	h_period = (h_period_est * v_refresh_est) /
+	h_period = ((long long)h_period_est * v_refresh_est) /
 		   (v_refresh * HV_FACTOR);
 
 	if (!reduced_blanking)
@@ -455,7 +454,7 @@ bool calc_gtf_modeline(int image_width, int image_height,
 				      GTF_S_M_PRIME * h_period / 1000;
 
 
-	h_blank = active_h_pixel * ideal_blank_duty_cycle /
+	h_blank = active_h_pixel * (long long)ideal_blank_duty_cycle /
 			 (100 * HV_FACTOR - ideal_blank_duty_cycle);
 	h_blank = ((h_blank + GTF_CELL_GRAN) / (2 * GTF_CELL_GRAN))
 			  * (2 * GTF_CELL_GRAN);
@@ -467,7 +466,6 @@ bool calc_gtf_modeline(int image_width, int image_height,
 
 	h_fp = h_blank / 2 - h_sync;
 	h_bp = h_fp + h_sync;
-
 	pixel_clock = ((long long)total_h_pixel * HV_FACTOR * 1000000)
 					/ h_period;
 	/* Not sure if clock value needs to be truncated to multiple
-- 
1.9.1