Re: [PATCH] media: iris: fix 64-bit division in iris_set_slice_count()

[Bryan O'Donoghue <bod@kernel.org>]

On 01/10/2026 01:46, Sasha Levin wrote:
> 32-bit ARM builds fail at modpost:
> 
>    ERROR: modpost: drivers/media/platform/qcom/iris/qcom-iris.ko:
>    symbol '__aeabi_ldivmod' undefined!
> 
> The maximum average slice size in MAX_BYTES mode is derived from the
> BITRATE capability, whose value is an s64, so both the division by
> the frame rate and the DIV_ROUND_UP() by the number of slices are
> 64-bit divisions. 32-bit ARM has no instruction for these and the
> compiler emits calls to __aeabi_ldivmod(), which the kernel does not
> provide.
> 
> The bitrate is always positive, so use div_u64() for the division by
> the frame rate and DIV_ROUND_UP_ULL() for the rounding. Include
> <linux/math64.h> for div_u64() instead of relying on it being pulled
> in indirectly.
> 
> Reported-by: kernelci.org bot <bot@kernelci.org>
> Closes: https://d.kernelci.org/i/maestro:4935f1aae20e7f957e60f8fde09c4e6d153c7909
> Fixes: 5f21cd9a4ae4 ("media: iris: add support for multi_slice in iris encoder")
> Assisted-by: LLM
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>   drivers/media/platform/qcom/iris/iris_ctrls.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/platform/qcom/iris/iris_ctrls.c b/drivers/media/platform/qcom/iris/iris_ctrls.c
> index 8c4c47944f22f..4f2633bbb49f8 100644
> --- a/drivers/media/platform/qcom/iris/iris_ctrls.c
> +++ b/drivers/media/platform/qcom/iris/iris_ctrls.c
> @@ -3,6 +3,7 @@
>    * Copyright (c) 2022-2024 Qualcomm Innovation Center, Inc. All rights reserved.
>    */
> 
> +#include <linux/math64.h>
>   #include <linux/types.h>
>   #include <media/v4l2-mem2mem.h>
> 
> @@ -1588,8 +1589,9 @@ int iris_set_slice_count(struct iris_inst *inst, enum platform_inst_fw_cap_type
>   	} else if (slice_mode == V4L2_MPEG_VIDEO_MULTI_SLICE_MODE_MAX_BYTES) {
>   		hfi_value = inst->fw_caps[SLICE_MAX_BYTES].value;
>   		if (rc_type != HFI_RC_OFF) {
> -			max_avg_slicesize = DIV_ROUND_UP((inst->fw_caps[BITRATE].value / fps) / 8,
> -							 slice_caps->max_slices_per_frame);
> +			max_avg_slicesize =
> +				DIV_ROUND_UP_ULL(div_u64(inst->fw_caps[BITRATE].value, fps) / 8,
> +						 slice_caps->max_slices_per_frame);
>   		} else {
>   			/*
>   			 * No bitrate target exists under RC_OFF, so approximate a
> --
> 2.53.0
> 
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>