media: atmel: atmel-isc: limit incoming pixels per frame

This will limit the incoming pixels per frame from the sensor.
Currently, the ISC will stop sampling the frame only when the vsync/hsync
are detected.
If we misconfigure the resolution in the sensor w.r.t. resolution in the ISC,
the buffer used for DMA in the ISC will be smaller than the number of pixels
that the ISC DMA engine will copy.
In this case it happens that the DMA will overwrite parts of the memory which
should not be written, leading to memory corruption.
To avoid this situation, use the PFE CFG1 and PFE CFG2 registers, which crop
the incoming frame to the resolution that we configure.
This way the DMA engine will never write more data than we expect it to.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/drivers/media/platform/atmel/atmel-isc.c b/drivers/media/platform/atmel/atmel-isc.c
index 4bba9da206e4..96ab8da0e4be 100644
--- a/drivers/media/platform/atmel/atmel-isc.c
+++ b/drivers/media/platform/atmel/atmel-isc.c
@@ -721,6 +721,40 @@ static void isc_start_dma(struct isc_device *isc)
 	u32 sizeimage = isc->fmt.fmt.pix.sizeimage;
 	u32 dctrl_dview;
 	dma_addr_t addr0;
+	u32 h, w;
+
+	h = isc->fmt.fmt.pix.height;
+	w = isc->fmt.fmt.pix.width;
+
+	/*
+	 * In case the sensor is not RAW, it will output a pixel (12-16 bits)
+	 * with two samples on the ISC Data bus (which is 8-12)
+	 * ISC will count each sample, so, we need to multiply these values
+	 * by two, to get the real number of samples for the required pixels.
+	 */
+	if (!ISC_IS_FORMAT_RAW(isc->config.sd_format->mbus_code)) {
+		h <<= 1;
+		w <<= 1;
+	}
+
+	/*
+	 * We limit the column/row count that the ISC will output according
+	 * to the configured resolution that we want.
+	 * This will avoid the situation where the sensor is misconfigured,
+	 * sending more data, and the ISC will just take it and DMA to memory,
+	 * causing corruption.
+	 */
+	regmap_write(regmap, ISC_PFE_CFG1,
+		     (ISC_PFE_CFG1_COLMIN(0) & ISC_PFE_CFG1_COLMIN_MASK) |
+		     (ISC_PFE_CFG1_COLMAX(w - 1) & ISC_PFE_CFG1_COLMAX_MASK));
+
+	regmap_write(regmap, ISC_PFE_CFG2,
+		     (ISC_PFE_CFG2_ROWMIN(0) & ISC_PFE_CFG2_ROWMIN_MASK) |
+		     (ISC_PFE_CFG2_ROWMAX(h - 1) & ISC_PFE_CFG2_ROWMAX_MASK));
+
+	regmap_update_bits(regmap, ISC_PFE_CFG0,
+			   ISC_PFE_CFG0_COLEN | ISC_PFE_CFG0_ROWEN,
+			   ISC_PFE_CFG0_COLEN | ISC_PFE_CFG0_ROWEN);
 
 	addr0 = vb2_dma_contig_plane_dma_addr(&isc->cur_frm->vb.vb2_buf, 0);
 	regmap_write(regmap, ISC_DAD0, addr0);