linux-kernel - [PATCH v2 2/2] media: iris: Fix fps calculation

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Message-Id: <20251216-warnings-6-19-v2-2-12075e3dece7@chromium.org>
Date: Tue, 16 Dec 2025 15:42:25 +0000
From: Ricardo Ribalda <ribalda@...omium.org>
To: Keke Li <keke.li@...ogic.com>, 
 Jacopo Mondi <jacopo.mondi@...asonboard.com>, 
 Daniel Scally <dan.scally@...asonboard.com>, 
 Hans Verkuil <hverkuil+cisco@...nel.org>, 
 Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>, 
 Vikash Garodia <vikash.garodia@....qualcomm.com>, 
 Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>, 
 Abhinav Kumar <abhinav.kumar@...ux.dev>, Bryan O'Donoghue <bod@...nel.org>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: Sakari Ailus <sakari.ailus@...ux.intel.com>, 
 linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-arm-msm@...r.kernel.org, Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH v2 2/2] media: iris: Fix fps calculation

iris_venc_s_param() uses do_div to divide two 64 bits operators, this is
wrong. Luckily for us, both of the operators fit in 32 bits, so we can use
a normal division.

Now that we are at it, mark the fps smaller than 1 as invalid, the code
does not seem to handle them properly.

The following cocci warning is fixed with this patch:
./platform/qcom/iris/iris_venc.c:378:1-7: WARNING: do_div() does a 64-by-32 division, please consider using div64_u64 instead

Fixes: 4ff586ff28e3 ("media: iris: Add support for G/S_PARM for encoder video device")
Reviewed-by: Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>
Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
 drivers/media/platform/qcom/iris/iris_venc.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/media/platform/qcom/iris/iris_venc.c b/drivers/media/platform/qcom/iris/iris_venc.c
index 5830eba93c68b27fa9db87bac63a691eaca338d2..3b941aeb55a2f498898a27a5f8cb58cdb26fdfed 100644
--- a/drivers/media/platform/qcom/iris/iris_venc.c
+++ b/drivers/media/platform/qcom/iris/iris_venc.c
@@ -382,8 +382,7 @@ int iris_venc_s_param(struct iris_inst *inst, struct v4l2_streamparm *s_parm)
 	struct v4l2_fract *timeperframe = NULL;
 	u32 default_rate = DEFAULT_FPS;
 	bool is_frame_rate = false;
-	u64 us_per_frame, fps;
-	u32 max_rate;
+	u32 fps, max_rate;
 
 	int ret = 0;
 
@@ -405,23 +404,19 @@ int iris_venc_s_param(struct iris_inst *inst, struct v4l2_streamparm *s_parm)
 			timeperframe->denominator = default_rate;
 	}
 
-	us_per_frame = timeperframe->numerator * (u64)USEC_PER_SEC;
-	do_div(us_per_frame, timeperframe->denominator);
-
-	if (!us_per_frame)
+	fps = timeperframe->numerator / timeperframe->denominator;
+	if (!fps)
 		return -EINVAL;
 
-	fps = (u64)USEC_PER_SEC;
-	do_div(fps, us_per_frame);
 	if (fps > max_rate) {
 		ret = -ENOMEM;
 		goto reset_rate;
 	}
 
 	if (is_frame_rate)
-		inst->frame_rate = (u32)fps;
+		inst->frame_rate = fps;
 	else
-		inst->operating_rate = (u32)fps;
+		inst->operating_rate = fps;
 
 	if ((s_parm->type == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE && vb2_is_streaming(src_q)) ||
 	    (s_parm->type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE && vb2_is_streaming(dst_q))) {

-- 
2.52.0.239.gd5f0c6e74e-goog