Even simpler:

On Sun, 4 Oct 2015, Guennadi Liakhovetski wrote:

Hi Josh,

On Tue, 22 Sep 2015, Josh Wu wrote:

quoted

we need to configure the YCC_SWAP bits in ISI_CFG2 according to current
sensor output and Atmel ISI output format.

Current there are two cases Atmel ISI supported:
  1. Atmel ISI outputs YUYV format.
     This case we need to setup YCC_SWAP according to sensor output
     format.
  2. Atmel ISI output a pass-through formats, which means no swap.
     Just setup YCC_SWAP as default with no swap.

Signed-off-by: Josh Wu <redacted>
---

 drivers/media/platform/soc_camera/atmel-isi.c | 43 ++++++++++++++++++++-------
 1 file changed, 33 insertions(+), 10 deletions(-)

diff --git a/drivers/media/platform/soc_camera/atmel-isi.c b/drivers/media/platform/soc_camera/atmel-isi.c
index 45e304a..df64294 100644
--- a/drivers/media/platform/soc_camera/atmel-isi.c
+++ b/drivers/media/platform/soc_camera/atmel-isi.c

@@ -103,13 +103,41 @@ static u32 isi_readl(struct atmel_isi *isi, u32 reg)
 	return readl(isi->regs + reg);
 }
 
+static u32 setup_cfg2_yuv_swap(struct atmel_isi *isi,
+		const struct soc_camera_format_xlate *xlate)
+{

This function will be called only for the four media codes from the 
switch-case statement below, namely for

MEDIA_BUS_FMT_VYUY8_2X8
MEDIA_BUS_FMT_UYVY8_2X8
MEDIA_BUS_FMT_YVYU8_2X8
MEDIA_BUS_FMT_YUYV8_2X8

quoted

+	/* By default, no swap for the codec path of Atmel ISI. So codec
+	* output is same as sensor's output.
+	* For instance, if sensor's output is YUYV, then codec outputs YUYV.
+	* And if sensor's output is UYVY, then codec outputs UYVY.
+	*/
+	u32 cfg2_yuv_swap = ISI_CFG2_YCC_SWAP_DEFAULT;

Then this ISI_CFG2_YCC_SWAP_DEFAULT will only hold for 
MEDIA_BUS_FMT_YUYV8_2X8? Why don't you just add one more case below? Don't 
think this initialisation is really justified.

quoted

+
+	if (xlate->host_fmt->fourcc == V4L2_PIX_FMT_YUYV) {
+		/* all convert to YUYV */
+		switch (xlate->code) {
+		case MEDIA_BUS_FMT_VYUY8_2X8:
+			cfg2_yuv_swap = ISI_CFG2_YCC_SWAP_MODE_3;
+			break;

Why don't you just return the result value here directly? Then you don't 
need the variable at all

quoted

+		case MEDIA_BUS_FMT_UYVY8_2X8:
+			cfg2_yuv_swap = ISI_CFG2_YCC_SWAP_MODE_2;
+			break;
+		case MEDIA_BUS_FMT_YVYU8_2X8:
+			cfg2_yuv_swap = ISI_CFG2_YCC_SWAP_MODE_1;
+			break;
+		}
+	}
+
+	return cfg2_yuv_swap;
+}
+
 static void configure_geometry(struct atmel_isi *isi, u32 width,
-			u32 height, u32 code)
+		u32 height, const struct soc_camera_format_xlate *xlate)
 {
 	u32 cfg2;
 
 	/* According to sensor's output format to set cfg2 */
-	switch (code) {
+	switch (xlate->code) {
 	default:
 	/* Grey */
 	case MEDIA_BUS_FMT_Y8_1X8:

@@ -117,16 +145,11 @@ static void configure_geometry(struct atmel_isi *isi, u32 width,
 		break;
 	/* YUV */
 	case MEDIA_BUS_FMT_VYUY8_2X8:
-		cfg2 = ISI_CFG2_YCC_SWAP_MODE_3 | ISI_CFG2_COL_SPACE_YCbCr;
-		break;
 	case MEDIA_BUS_FMT_UYVY8_2X8:
-		cfg2 = ISI_CFG2_YCC_SWAP_MODE_2 | ISI_CFG2_COL_SPACE_YCbCr;
-		break;
 	case MEDIA_BUS_FMT_YVYU8_2X8:
-		cfg2 = ISI_CFG2_YCC_SWAP_MODE_1 | ISI_CFG2_COL_SPACE_YCbCr;
-		break;
 	case MEDIA_BUS_FMT_YUYV8_2X8:
-		cfg2 = ISI_CFG2_YCC_SWAP_DEFAULT | ISI_CFG2_COL_SPACE_YCbCr;
+		cfg2 = ISI_CFG2_COL_SPACE_YCbCr |
+				setup_cfg2_yuv_swap(isi, xlate);
 		break;
 	/* RGB, TODO */
 	}

I would move this switch-case completely inside setup_cfg2_yuv_swap(). 
Just do

	cfg2 = setup_cfg2_yuv_swap(isi, xlate);

and handle the

 	case MEDIA_BUS_FMT_Y8_1X8:

in the function too. These two switch-case statements really look 
redundant.

quoted

@@ -407,7 +430,7 @@ static int start_streaming(struct vb2_queue *vq, unsigned int count)
 	isi_writel(isi, ISI_INTDIS, (u32)~0UL);
 
 	configure_geometry(isi, icd->user_width, icd->user_height,
-				icd->current_fmt->code);
+				icd->current_fmt);
 
 	spin_lock_irq(&isi->lock);
 	/* Clear any pending interrupt */

-- 
1.9.1

Thanks
Guennadi