From: Martin Bugge <marbugge@xxxxxxxxx>
This patch fixes two errors that caused incorrect format detections:
The first bug is in the calculation of the vertical backporch: the combined
period of vsync and backporch must *exceed* a certain minimum value, and not
be equal to it.
The second bug is a rounding error in the reduced blanking calculation:
expand the ideal_duty_cylce to be in parts per ten thousand to avoid
rounding errors.
Signed-off-by: Martin Bugge <marbugge@xxxxxxxxx>
Cc: Mats Randgaard <matrandg@xxxxxxxxx>
Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
---
drivers/media/v4l2-core/v4l2-dv-timings.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)
diff --git a/drivers/media/v4l2-core/v4l2-dv-timings.c b/drivers/media/v4l2-core/v4l2-dv-timings.c
index f20b316..72cf224 100644
--- a/drivers/media/v4l2-core/v4l2-dv-timings.c
+++ b/drivers/media/v4l2-core/v4l2-dv-timings.c
@@ -286,14 +286,14 @@ 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 + 999999) / 1000000;
+ v_bp = (CVT_RB_MIN_V_BLANK * hfreq + 1999999) / 1000000;
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 + 999999) / 1000000 - vsync;
+ v_bp = (CVT_MIN_VSYNC_BP * hfreq + 1999999) / 1000000 - vsync;
if (v_bp < CVT_MIN_V_BPORCH)
v_bp = CVT_MIN_V_BPORCH;
@@ -337,17 +337,16 @@ bool v4l2_detect_cvt(unsigned frame_height, unsigned hfreq, unsigned vsync,
frame_width = image_width + CVT_RB_H_BLANK;
} else {
+ unsigned ideal_duty_cycle_per_myriad =
+ 100 * CVT_C_PRIME - (CVT_M_PRIME * 100000) / hfreq;
int h_blank;
- unsigned ideal_duty_cycle = CVT_C_PRIME - (CVT_M_PRIME * 1000) / hfreq;
- h_blank = (image_width * ideal_duty_cycle + (100 - ideal_duty_cycle) / 2) /
- (100 - ideal_duty_cycle);
- h_blank = h_blank - h_blank % (2 * CVT_CELL_GRAN);
+ if (ideal_duty_cycle_per_myriad < 2000)
+ ideal_duty_cycle_per_myriad = 2000;
- if (h_blank * 100 / image_width < 20) {
- h_blank = image_width / 5;
- h_blank = (h_blank + 0x7) & ~0x7;
- }
+ h_blank = image_width * ideal_duty_cycle_per_myriad /
+ (10000 - ideal_duty_cycle_per_myriad);
+ h_blank = (h_blank / (2 * CVT_CELL_GRAN)) * 2 * CVT_CELL_GRAN;
pix_clk = (image_width + h_blank) * hfreq;
pix_clk = (pix_clk / CVT_PXL_CLK_GRAN) * CVT_PXL_CLK_GRAN;
--
1.8.3.2
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