[PATCH v4 4/7] media: imx: imx-mipi-csis: Set PIXEL_MODE for YUV422

[Jacopo Mondi]

Bits 13 and 12 of the ISP_CONFIGn register configure the PIXEL_MODE
which specifies the sampling size, in pixel component units, on the
CSI-2 output data interface when data are transferred to memory.

The register description in the chip manual specifies that DUAL mode
should be used for YUV422 data.

Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
Signed-off-by: Xavier Roumegue <xavier.roumegue at oss.nxp.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 drivers/media/platform/imx/imx-mipi-csis.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/imx/imx-mipi-csis.c b/drivers/media/platform/imx/imx-mipi-csis.c
index 3e7efcf43a5f..9d5034759987 100644
--- a/drivers/media/platform/imx/imx-mipi-csis.c
+++ b/drivers/media/platform/imx/imx-mipi-csis.c
@@ -173,6 +173,7 @@
 #define MIPI_CSIS_ISPCFG_PIXEL_MODE_SINGLE	(0 << 12)
 #define MIPI_CSIS_ISPCFG_PIXEL_MODE_DUAL	(1 << 12)
 #define MIPI_CSIS_ISPCFG_PIXEL_MODE_QUAD	(2 << 12)	/* i.MX8M[MNP] only */
+#define MIPI_CSIS_ISPCFG_PIXEL_MASK		(3 << 12)
 #define MIPI_CSIS_ISPCFG_ALIGN_32BIT		BIT(11)
 #define MIPI_CSIS_ISPCFG_FMT(fmt)		((fmt) << 2)
 #define MIPI_CSIS_ISPCFG_FMT_MASK		(0x3f << 2)
@@ -506,7 +507,25 @@ static void __mipi_csis_set_format(struct csi_state *state)
 
 	/* Color format */
 	val = mipi_csis_read(state, MIPI_CSIS_ISP_CONFIG_CH(0));
-	val &= ~(MIPI_CSIS_ISPCFG_ALIGN_32BIT | MIPI_CSIS_ISPCFG_FMT_MASK);
+	val &= ~(MIPI_CSIS_ISPCFG_ALIGN_32BIT | MIPI_CSIS_ISPCFG_FMT_MASK
+		| MIPI_CSIS_ISPCFG_PIXEL_MASK);
+
+	/*
+	 * YUV 4:2:2 can be transferred with 8 or 16 bits per clock sample
+	 * (referred to in the documentation as single and dual pixel modes
+	 * respectively, although the 8-bit mode transfers half a pixel per
+	 * clock sample and the 16-bit mode one pixel). While both mode work
+	 * when the CSIS is connected to a receiver that supports either option,
+	 * single pixel mode requires clock rates twice as high. As all SoCs
+	 * that integrate the CSIS can operate in 16-bit bit mode, and some do
+	 * not support 8-bit mode (this is the case of the i.MX8MP), use dual
+	 * pixel mode unconditionally.
+	 *
+	 * TODO: Verify which other formats require DUAL (or QUAD) modes.
+	 */
+	if (state->csis_fmt->data_type == MIPI_CSI2_DATA_TYPE_YUV422_8)
+		val |= MIPI_CSIS_ISPCFG_PIXEL_MODE_DUAL;
+
 	val |= MIPI_CSIS_ISPCFG_FMT(state->csis_fmt->data_type);
 	mipi_csis_write(state, MIPI_CSIS_ISP_CONFIG_CH(0), val);
 
-- 
2.35.0