Re: [PATCH v2 1/5] media: mt9p031: Add support for 8 bit and 10 bit formats

Stefan Riedmüller <s.riedmueller@xxxxxxxxx> · Mon, 5 Oct 2020 11:31:59 +0200

Hi Laurent,

On 02.10.20 01:53, Laurent Pinchart wrote:
Hi Stefan,

On Thu, Oct 01, 2020 at 11:07:00AM +0200, Stefan Riedmüller wrote:
On 30.09.20 13:42, Laurent Pinchart wrote:
On Wed, Sep 30, 2020 at 12:51:29PM +0200, Stefan Riedmueller wrote:
From: Christian Hemp <c.hemp@xxxxxxxxx>

Aside from 12 bit monochrome or color format the sensor implicitly
supports 10 and 8 bit formats as well by simply dropping the
corresponding LSBs.

That's not how it should work though. If you set the format on
MEDIA_BUS_FMT_SGRBG8_1X8 through the pipeline for instance, you will end
up capturing the 8 LSB, not the 8 MSB.

What's your use case for this ?

I use this sensor in combination with an i.MX 6 and i.MX 6UL. When the
sensor is connected with 12 bit (or 10 bit on the i.MX 6UL) and I set
MEDIA_BUS_FMT_SGRBG8_1X8 through the pipeline the CSI interface drops the
unused 4 LSB (or 2 LSB on the i.MX 6UL) so I get the 8 MSB from my 12 bit
sensor.

Is that the PIXEL_BIT bit in CSI_CSICR1 for the i.MX6UL ? If so I think
this should be handled in the imx7-media-csi driver. You could set the
format to MEDIA_BUS_FMT_SGRBG10_1X10 on the sink pad of the CSI and to
MEDIA_BUS_FMT_SGRBG8_1X8 on the source pad to configure this. I don't
think the sensor driver should be involved, otherwise we'd have to patch
all sensor drivers. From a sensor point of view, it outputs 12-bit
Bayer, not 8-bit.

Ah, I had it wrong. What you say makes total sense. I will take another look 
at it and also try to work your suggestion from below in.

Thanks,
Stefan


Now there's a caveat. When used with the i.MX6UL, I assume you connected
D[11:2] of the sensor to D[9:0] of the i.MX6UL, right ? The i.MX6UL
doesn't support 12-bit inputs, so it should accept
MEDIA_BUS_FMT_SGRBG12_1X12 on its sink pad. In this case, as D[1:0] of
the sensor are left unconnected, I think you should set data-shift to 2
and bus-width to 10 in DT on the sensor side. The MT9P031 driver should
parse that, and output MEDIA_BUS_FMT_SGRBG10_1X10 instead of
MEDIA_BUS_FMT_SGRBG12_1X12 in that case.

Does this clarify things? Maybe the description in the commit message is not
accurate enough or did I get something wrong?

Signed-off-by: Christian Hemp <c.hemp@xxxxxxxxx>
[jlu@xxxxxxxxxxxxxx: simplified by dropping v4l2_colorspace handling]
Signed-off-by: Jan Luebbe <jlu@xxxxxxxxxxxxxx>
Signed-off-by: Stefan Riedmueller <s.riedmueller@xxxxxxxxx>
---
Changes in v2:
   - Use unsigned int for num_fmts and loop variable in find_datafmt
   - Remove superfluous const qualifier from find_datafmt
---
   drivers/media/i2c/mt9p031.c | 50 +++++++++++++++++++++++++++++--------
   1 file changed, 40 insertions(+), 10 deletions(-)

diff --git a/drivers/media/i2c/mt9p031.c b/drivers/media/i2c/mt9p031.c
index dc23b9ed510a..2e6671ef877c 100644
--- a/drivers/media/i2c/mt9p031.c
+++ b/drivers/media/i2c/mt9p031.c
@@ -116,6 +116,18 @@ enum mt9p031_model {
   	MT9P031_MODEL_MONOCHROME,
   };
   
+static const u32 mt9p031_color_fmts[] = {
+	MEDIA_BUS_FMT_SGRBG8_1X8,
+	MEDIA_BUS_FMT_SGRBG10_1X10,
+	MEDIA_BUS_FMT_SGRBG12_1X12,
+};
+
+static const u32 mt9p031_monochrome_fmts[] = {
+	MEDIA_BUS_FMT_Y8_1X8,
+	MEDIA_BUS_FMT_Y10_1X10,
+	MEDIA_BUS_FMT_Y12_1X12,
+};
+
   struct mt9p031 {
   	struct v4l2_subdev subdev;
   	struct media_pad pad;
@@ -138,6 +150,9 @@ struct mt9p031 {
   	struct v4l2_ctrl *blc_auto;
   	struct v4l2_ctrl *blc_offset;
   
+	const u32 *fmts;
+	unsigned int num_fmts;
+
   	/* Registers cache */
   	u16 output_control;
   	u16 mode2;
@@ -148,6 +163,17 @@ static struct mt9p031 *to_mt9p031(struct v4l2_subdev *sd)
   	return container_of(sd, struct mt9p031, subdev);
   }
   
+static u32 mt9p031_find_datafmt(struct mt9p031 *mt9p031, u32 code)
+{
+	unsigned int i;
+
+	for (i = 0; i < mt9p031->num_fmts; i++)
+		if (mt9p031->fmts[i] == code)
+			return mt9p031->fmts[i];
+
+	return mt9p031->fmts[mt9p031->num_fmts-1];
+}
+
   static int mt9p031_read(struct i2c_client *client, u8 reg)
   {
   	return i2c_smbus_read_word_swapped(client, reg);
@@ -476,10 +502,11 @@ static int mt9p031_enum_mbus_code(struct v4l2_subdev *subdev,
   {
   	struct mt9p031 *mt9p031 = to_mt9p031(subdev);
   
-	if (code->pad || code->index)
+	if (code->pad || code->index >= mt9p031->num_fmts)
   		return -EINVAL;
   
-	code->code = mt9p031->format.code;
+	code->code = mt9p031->fmts[code->index];
+
   	return 0;
   }
   
@@ -573,6 +600,8 @@ static int mt9p031_set_format(struct v4l2_subdev *subdev,
   	__format->width = __crop->width / hratio;
   	__format->height = __crop->height / vratio;
   
+	__format->code = mt9p031_find_datafmt(mt9p031, format->format.code);
+
   	format->format = *__format;
   
   	return 0;
@@ -951,10 +980,7 @@ static int mt9p031_open(struct v4l2_subdev *subdev, struct v4l2_subdev_fh *fh)
   
   	format = v4l2_subdev_get_try_format(subdev, fh->pad, 0);
   
-	if (mt9p031->model == MT9P031_MODEL_MONOCHROME)
-		format->code = MEDIA_BUS_FMT_Y12_1X12;
-	else
-		format->code = MEDIA_BUS_FMT_SGRBG12_1X12;
+	format->code = mt9p031_find_datafmt(mt9p031, 0);
   
   	format->width = MT9P031_WINDOW_WIDTH_DEF;
   	format->height = MT9P031_WINDOW_HEIGHT_DEF;
@@ -1121,10 +1147,14 @@ static int mt9p031_probe(struct i2c_client *client,
   	mt9p031->crop.left = MT9P031_COLUMN_START_DEF;
   	mt9p031->crop.top = MT9P031_ROW_START_DEF;
   
-	if (mt9p031->model == MT9P031_MODEL_MONOCHROME)
-		mt9p031->format.code = MEDIA_BUS_FMT_Y12_1X12;
-	else
-		mt9p031->format.code = MEDIA_BUS_FMT_SGRBG12_1X12;
+	if (mt9p031->model == MT9P031_MODEL_MONOCHROME) {
+		mt9p031->fmts = mt9p031_monochrome_fmts;
+		mt9p031->num_fmts = ARRAY_SIZE(mt9p031_monochrome_fmts);
+	} else {
+		mt9p031->fmts = mt9p031_color_fmts;
+		mt9p031->num_fmts = ARRAY_SIZE(mt9p031_color_fmts);
+	}
+	mt9p031->format.code = mt9p031_find_datafmt(mt9p031, 0);
   
   	mt9p031->format.width = MT9P031_WINDOW_WIDTH_DEF;
   	mt9p031->format.height = MT9P031_WINDOW_HEIGHT_DEF;








