From: Guoniu Zhou <guoniu.zhou@nxp.com>

The maximum downscaling factor supported by ISI can be up to 16. Add
minimum value constraint before applying the setting to hardware.
Otherwise, the process will not respond even when Ctrl+C is executed.

Fixes: cf21f328fcaf ("media: nxp: Add i.MX8 ISI driver")
Cc: stable@vger.kernel.org
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Guoniu Zhou <guoniu.zhou@nxp.com>
---
Changes in v3:
- Replace CLAMP_DOWNSCALE_16 macro with inline function
- Adjust downscale threshold from 0x4000 to 0x2000
- Clarify downscaling limit in comment
---
 drivers/media/platform/nxp/imx8-isi/imx8-isi-core.h | 16 ++++++++++++++++
 drivers/media/platform/nxp/imx8-isi/imx8-isi-hw.c   |  2 +-
 drivers/media/platform/nxp/imx8-isi/imx8-isi-m2m.c  | 11 ++++++++---
 drivers/media/platform/nxp/imx8-isi/imx8-isi-pipe.c | 13 ++++++++-----
 4 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.h b/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.h
index 3cbd35305af0..822466445b72 100644
--- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.h
+++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.h
@@ -11,6 +11,7 @@
 #define __MXC_ISI_CORE_H__
 
 #include <linux/list.h>
+#include <linux/math.h>
 #include <linux/mutex.h>
 #include <linux/spinlock.h>
 #include <linux/types.h>
@@ -413,4 +414,19 @@ static inline void mxc_isi_debug_cleanup(struct mxc_isi_dev *isi)
 }
 #endif
 
+/*
+ * ISI scaling engine works in two parts: it performs pre-decimation of
+ * the image followed by bilinear filtering to achieve the desired
+ * downscaling factor.
+ *
+ * The decimation filter provides a maximum downscaling factor of 8, and
+ * the subsequent bilinear filter provides a maximum downscaling factor
+ * of 2. Combined, the maximum scaling factor can be up to 16.
+ */
+static inline unsigned int
+mxc_isi_clamp_downscale_16(unsigned int val, unsigned int max_val)
+{
+	return clamp(val, max(1U, DIV_ROUND_UP(max_val, 16)), max_val);
+}
+
 #endif /* __MXC_ISI_CORE_H__ */
diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-hw.c b/drivers/media/platform/nxp/imx8-isi/imx8-isi-hw.c
index 9225a7ac1c3e..37e59d687ed7 100644
--- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-hw.c
+++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-hw.c
@@ -11,7 +11,7 @@
 #include "imx8-isi-core.h"
 #include "imx8-isi-regs.h"
 
-#define	ISI_DOWNSCALE_THRESHOLD		0x4000
+#define	ISI_DOWNSCALE_THRESHOLD		0x2000
 
 static inline u32 mxc_isi_read(struct mxc_isi_pipe *pipe, u32 reg)
 {
diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-m2m.c b/drivers/media/platform/nxp/imx8-isi/imx8-isi-m2m.c
index a39ad7a1ab18..a0e2061f4344 100644
--- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-m2m.c
+++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-m2m.c
@@ -508,10 +508,15 @@ __mxc_isi_m2m_try_fmt_vid(struct mxc_isi_m2m_ctx *ctx,
 			  struct v4l2_pix_format_mplane *pix,
 			  const enum mxc_isi_video_type type)
 {
+	const struct v4l2_pix_format_mplane *format =
+		&ctx->queues.out.format;
+
 	if (type == MXC_ISI_VIDEO_M2M_CAP) {
-		/* Downscaling only  */
-		pix->width = min(pix->width, ctx->queues.out.format.width);
-		pix->height = min(pix->height, ctx->queues.out.format.height);
+		/* Downscaling only, by up to 16. */
+		pix->width = mxc_isi_clamp_downscale_16(pix->width,
+							format->width);
+		pix->height = mxc_isi_clamp_downscale_16(pix->height,
+							 format->height);
 	}
 
 	return mxc_isi_format_try(ctx->m2m->pipe, pix, type);
diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-pipe.c b/drivers/media/platform/nxp/imx8-isi/imx8-isi-pipe.c
index a41c51dd9ce0..b290821d03d2 100644
--- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-pipe.c
+++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-pipe.c
@@ -641,16 +641,19 @@ static int mxc_isi_pipe_set_selection(struct v4l2_subdev *sd,
 			/* Composing is supported on the sink only. */
 			return -EINVAL;
 
-		/* The sink crop is bound by the sink format downscaling only). */
+		/*
+		 * The ISI supports downscaling only, with a factor up to 16.
+		 * Clamp the compose rectangle size accordingly.
+		 */
 		format = mxc_isi_pipe_get_pad_format(pipe, state,
 						     MXC_ISI_PIPE_PAD_SINK);
 
 		sel->r.left = 0;
 		sel->r.top = 0;
-		sel->r.width = clamp(sel->r.width, MXC_ISI_MIN_WIDTH,
-				     format->width);
-		sel->r.height = clamp(sel->r.height, MXC_ISI_MIN_HEIGHT,
-				      format->height);
+		sel->r.width = mxc_isi_clamp_downscale_16(sel->r.width,
+							  format->width);
+		sel->r.height = mxc_isi_clamp_downscale_16(sel->r.height,
+							   format->height);
 
 		rect = mxc_isi_pipe_get_pad_compose(pipe, state,
 						    MXC_ISI_PIPE_PAD_SINK);

-- 
2.34.1