[PATCH] media: stm32-dcmi: add support of BT656 bus

[Hugues Fruchet]

Add support of BT656 embedded synchronization bus.
This mode allows to save hardware synchro lines hsync & vsync
by replacing them with synchro codes embedded in data stream.
This bus type is only compatible with 8 bits width data bus.
Due to reserved values 0x00 & 0xff used for synchro codes,
valid data only vary from 0x1 to 0xfe, this is up to sensor
to clip accordingly pixel data. As a consequence of this
clipping, JPEG is not supported when using this bus type.
DCMI crop feature is also not available with this bus type.

Signed-off-by: Hugues Fruchet <hugues.fruchet@xxxxxx>
---
 drivers/media/platform/stm32/stm32-dcmi.c | 37 +++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/stm32/stm32-dcmi.c b/drivers/media/platform/stm32/stm32-dcmi.c
index fd1c41c..d7d7cdb 100644
--- a/drivers/media/platform/stm32/stm32-dcmi.c
+++ b/drivers/media/platform/stm32/stm32-dcmi.c
@@ -157,6 +157,7 @@ struct stm32_dcmi {
 	struct vb2_queue		queue;
 
 	struct v4l2_fwnode_bus_parallel	bus;
+	enum v4l2_mbus_type		bus_type;
 	struct completion		complete;
 	struct clk			*mclk;
 	enum state			state;
@@ -777,6 +778,23 @@ static int dcmi_start_streaming(struct vb2_queue *vq, unsigned int count)
 	if (dcmi->bus.flags & V4L2_MBUS_PCLK_SAMPLE_RISING)
 		val |= CR_PCKPOL;
 
+	/*
+	 * BT656 embedded synchronisation bus mode.
+	 *
+	 * Default SAV/EAV mode is supported here with default codes
+	 * SAV=0xff000080 & EAV=0xff00009d.
+	 * With DCMI this means LSC=SAV=0x80 & LEC=EAV=0x9d.
+	 */
+	if (dcmi->bus_type == V4L2_MBUS_BT656) {
+		val |= CR_ESS;
+
+		/* Unmask all codes */
+		reg_write(dcmi->regs, DCMI_ESUR, 0xffffffff);/* FEC:LEC:LSC:FSC */
+
+		/* Trig on LSC=0x80 & LEC=0x9d codes, ignore FSC and FEC */
+		reg_write(dcmi->regs, DCMI_ESCR, 0xff9d80ff);/* FEC:LEC:LSC:FSC */
+	}
+
 	reg_write(dcmi->regs, DCMI_CR, val);
 
 	/* Set crop */
@@ -1067,8 +1085,9 @@ static int dcmi_set_fmt(struct stm32_dcmi *dcmi, struct v4l2_format *f)
 	if (ret)
 		return ret;
 
-	/* Disable crop if JPEG is requested */
-	if (pix->pixelformat == V4L2_PIX_FMT_JPEG)
+	/* Disable crop if JPEG is requested or BT656 bus is selected */
+	if (pix->pixelformat == V4L2_PIX_FMT_JPEG &&
+	    dcmi->bus_type != V4L2_MBUS_BT656)
 		dcmi->do_crop = false;
 
 	/* pix to mbus format */
@@ -1592,6 +1611,11 @@ static int dcmi_formats_init(struct stm32_dcmi *dcmi)
 			if (dcmi_formats[i].mbus_code != mbus_code.code)
 				continue;
 
+			/* Exclude JPEG if BT656 bus is selected */
+			if (dcmi_formats[i].fourcc == V4L2_PIX_FMT_JPEG &&
+			    dcmi->bus_type == V4L2_MBUS_BT656)
+				continue;
+
 			/* Code supported, have we got this fourcc yet? */
 			for (j = 0; j < num_fmts; j++)
 				if (sd_fmts[j]->fourcc ==
@@ -1873,9 +1897,18 @@ static int dcmi_probe(struct platform_device *pdev)
 		dev_err(&pdev->dev, "CSI bus not supported\n");
 		return -ENODEV;
 	}
+
+	if (ep.bus_type == V4L2_MBUS_BT656 &&
+	    ep.bus.parallel.bus_width != 8) {
+		dev_err(&pdev->dev, "BT656 bus conflicts with %d bits bus width (8 bits required)\n",
+			ep.bus.parallel.bus_width);
+		return -ENODEV;
+	}
+
 	dcmi->bus.flags = ep.bus.parallel.flags;
 	dcmi->bus.bus_width = ep.bus.parallel.bus_width;
 	dcmi->bus.data_shift = ep.bus.parallel.data_shift;
+	dcmi->bus_type = ep.bus_type;
 
 	irq = platform_get_irq(pdev, 0);
 	if (irq <= 0)
-- 
2.7.4