media: imx: imx-mipi-csis: Set PIXEL_MODE for YUV422

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@jmondi.org>
Signed-off-by: Xavier Roumegue <xavier.roumegue@oss.nxp.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

diff --git a/drivers/media/platform/imx/imx-mipi-csis.c b/drivers/media/platform/imx/imx-mipi-csis.c
index 100722b..5873ff7 100644 (file)
--- 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);