[PATCH v3 3/7] media: imx: imx7-media-csi: Use dual sampling for YUV 1X16

[Laurent Pinchart]

Hi Jacopo,

Thank you for the patch.

On Mon, Feb 21, 2022 at 12:04:32PM +0100, Jacopo Mondi wrote:
> The CSI bridge should operate in dual components mode when it is
> connected to a pixel transmitter that transfers two components at a time
> in YUV 422 formats (16 bits, Y + U/V).
> 
> Use the image format variants to determine if single or dual component mode
> should be used.
> 
> Add a note to the TODO file to record that the list of supported formats
> should be restricted to the SoC model the CSI bridge is integrated on
> to avoid potential pipeline mis-configurations.
> 
> Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
>  drivers/staging/media/imx/TODO             | 25 +++++++++++++++
>  drivers/staging/media/imx/imx7-media-csi.c | 37 +++++++++++++++++++---
>  2 files changed, 58 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/staging/media/imx/TODO b/drivers/staging/media/imx/TODO
> index 06c94f20ecf8..5d3a337c8702 100644
> --- a/drivers/staging/media/imx/TODO
> +++ b/drivers/staging/media/imx/TODO
> @@ -27,3 +27,28 @@
>  - i.MX7: all of the above, since it uses the imx media core
>  
>  - i.MX7: use Frame Interval Monitor
> +
> +- imx7-media-csi: Restrict the supported formats list to the SoC version.
> +
> +  The imx7 CSI bridge can be configured to sample pixel components from the Rx
> +  queue in single (8bpp) or double (16bpp) component modes. Image format
> +  variants with different sample sizes (ie YUYV_2X8 vs YUYV_1X16) determine the
> +  pixel components sampling size per each clock cycle and their packing mode
> +  (see imx7_csi_configure() for details).
> +
> +  As the imx7 CSI bridge can be interfaced with different IP blocks depending on
> +  the SoC model it is integrated on, the Rx queue sampling size should match
> +  the size of the samples transferred by the transmitting IP block.
> +
> +  To avoid mis-configurations of the capture pipeline, the enumeration of the
> +  supported formats should be restricted to match the pixel source transmitting
> +  mode.
> +
> +  Example: i.MX8MM SoC integrates the CSI bridge with the Samsung CSIS CSI-2
> +  receiver which operates in dual pixel sampling mode. The CSI bridge should
> +  only expose the 1X16 formats variant which instructs it to operate in dual
> +  pixel sampling mode. When the CSI bridge is instead integrated on an i.MX7,
> +  which supports both serial and parallel input, it should expose both variants.
> +
> +  This currently only applies to YUYV formats, but other formats might need
> +  to be handled in the same way.
> diff --git a/drivers/staging/media/imx/imx7-media-csi.c b/drivers/staging/media/imx/imx7-media-csi.c
> index 32311fc0e2a4..cf57157872b0 100644
> --- a/drivers/staging/media/imx/imx7-media-csi.c
> +++ b/drivers/staging/media/imx/imx7-media-csi.c
> @@ -498,16 +498,45 @@ static void imx7_csi_configure(struct imx7_csi *csi)
>  			cr3 |= BIT_TWO_8BIT_SENSOR;
>  			cr18 |= BIT_MIPI_DATA_FORMAT_RAW14;
>  			break;
> +
>  		/*
> -		 * CSI-2 sources are supposed to use the 1X16 formats, but not
> -		 * all of them comply. Support both variants.
> +		 * The CSI bridge has a 16-bit input bus. Depending on
> +		 * the connected source, data may be transmitted with 8
> +		 * or 10 bits per clock sample (in bits [9:2] or [9:0]
> +		 * respectively) or with 16 bits per clock sample (in
> +		 * bits [15:0]). The data is then packed into a 32-bit
> +		 * FIFO (as shown in figure 13-11 of the i.MX8MM
> +		 * reference manual rev. 3).
> +		 *
> +		 * The data packing in a 32-bit FIFO input word is
> +		 * controlled by the CR3 TWO_8BIT_SENSOR field (also
> +		 * known as SENSOR_16BITS in the i.MX8MM reference
> +		 * manual). When set to 0, data packing groups four
> +		 * 8-bit input samples (bits [9:2]). When set to 1, data
> +		 * packing groups two 16-bit input samples (bits
> +		 * [15:0]).
> +		 *
> +		 * The register field CR18 MIPI_DOUBLE_CMPNT also needs
> +		 * to be configured according to the input format for
> +		 * YUV 4:2:2 data. The field controls the gasket between
> +		 * the CSI-2 receiver and the CSI bridge. On i.MX7 and
> +		 * i.MX8MM, the field must be set to 1 when the CSIS
> +		 * outputs 16-bit samples. On i.MX8MQ, the gasket
> +		 * ignores the MIPI_DOUBLE_CMPNT bit and YUV 4:2:2
> +		 * always uses 16-bit samples. Setting MIPI_DOUBLE_CMPNT
> +		 * in that case has no effect, but doesn't cause any
> +		 * issue.

You may want to reflow this text to 80 columns.

>  		 */
>  		case MEDIA_BUS_FMT_UYVY8_2X8:
> -		case MEDIA_BUS_FMT_UYVY8_1X16:
>  		case MEDIA_BUS_FMT_YUYV8_2X8:
> -		case MEDIA_BUS_FMT_YUYV8_1X16:
>  			cr18 |= BIT_MIPI_DATA_FORMAT_YUV422_8B;
>  			break;
> +		case MEDIA_BUS_FMT_UYVY8_1X16:
> +		case MEDIA_BUS_FMT_YUYV8_1X16:
> +			cr3 |= BIT_TWO_8BIT_SENSOR;
> +			cr18 |= BIT_MIPI_DATA_FORMAT_YUV422_8B |
> +				BIT_MIPI_DOUBLE_CMPNT;
> +			break;
>  		}
>  	}
>  

-- 
Regards,

Laurent Pinchart