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media: nxp: imx8-isi: Fix scale factor calculation for hardware rounding

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The ISI hardware rounds the actual output size up to an integer, as
described in i.MX93 Reference Manual section 57.7.8 (Channel 0 Scale
Factor). The scale factor must be calculated to ensure the theoretical
output value rounds up to exactly the desired size.

Fixes: cf21f328fc ("media: nxp: Add i.MX8 ISI driver")
Cc: stable@vger.kernel.org
Signed-off-by: Guoniu Zhou <guoniu.zhou@nxp.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patch.msgid.link/20260323-isi-v3-2-8df53b24e622@oss.nxp.com
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
This commit is contained in:
Guoniu Zhou 2026-03-23 16:33:31 +08:00 committed by Hans Verkuil
parent 57a7ec5c9f
commit 5eb54da3f8
1 changed files with 8 additions and 1 deletions
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9
drivers/media/platform/nxp/imx8-isi/imx8-isi-hw.c
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@ -112,7 +112,14 @@ static u32 mxc_isi_channel_scaling_ratio(unsigned int from, unsigned int to,
else
*dec = 8;
return min_t(u32, from * 0x1000 / (to * *dec), ISI_DOWNSCALE_THRESHOLD);
/*
* The ISI rounds output dimensions up to the next integer (i.MX93 RM
* section 57.7.8). Calculate the scale factor such that the theoretical
* output (input / scale_factor) rounds up to exactly the desired
* output.
*/
return min_t(u32, DIV_ROUND_UP(from * 0x1000, to * *dec),
ISI_DOWNSCALE_THRESHOLD);
}
static void mxc_isi_channel_set_scaling(struct mxc_isi_pipe *pipe,