7.10. The mgb4 driver

7.10.1. sysfs interface

The mgb4 driver provides a sysfs interface, that is used to configure video stream related parameters (some of them must be set properly before the v4l2 device can be opened) and obtain the video device/stream status.

There are two types of parameters - global / PCI card related, found under /sys/class/video4linux/videoX/device and module specific found under /sys/class/video4linux/videoX.

7.10.1.1. Global (PCI card) parameters

module_type (R):

Module type.

0 - No module present

1 - FPDL3

2 - GMSL

module_version (R):

Module version number. Zero in case of a missing module.

fw_type (R):

Firmware type.

1 - FPDL3

2 - GMSL

fw_version (R):

Firmware version number.

serial_number (R):

Card serial number. The format is:

PRODUCT-REVISION-SERIES-SERIAL

where each component is a 8b number.

7.10.1.2. Common FPDL3/GMSL input parameters

input_id (R):

Input number ID, zero based.

oldi_lane_width (RW):

Number of deserializer output lanes.

0 - single

1 - dual (default)

color_mapping (RW):

Mapping of the incoming bits in the signal to the colour bits of the pixels.

0 - OLDI/JEIDA

1 - SPWG/VESA (default)

link_status (R):

Video link status. If the link is locked, chips are properly connected and communicating at the same speed and protocol. The link can be locked without an active video stream.

A value of 0 is equivalent to the V4L2_IN_ST_NO_SYNC flag of the V4L2 VIDIOC_ENUMINPUT status bits.

0 - unlocked

1 - locked

stream_status (R):

Video stream status. A stream is detected if the link is locked, the input pixel clock is running and the DE signal is moving.

A value of 0 is equivalent to the V4L2_IN_ST_NO_SIGNAL flag of the V4L2 VIDIOC_ENUMINPUT status bits.

0 - not detected

1 - detected

video_width (R):

Video stream width. This is the actual width as detected by the HW.

The value is identical to what VIDIOC_QUERY_DV_TIMINGS returns in the width field of the v4l2_bt_timings struct.

video_height (R):

Video stream height. This is the actual height as detected by the HW.

The value is identical to what VIDIOC_QUERY_DV_TIMINGS returns in the height field of the v4l2_bt_timings struct.

vsync_status (R):

The type of VSYNC pulses as detected by the video format detector.

The value is equivalent to the flags returned by VIDIOC_QUERY_DV_TIMINGS in the polarities field of the v4l2_bt_timings struct.

0 - active low

1 - active high

2 - not available

hsync_status (R):

The type of HSYNC pulses as detected by the video format detector.

The value is equivalent to the flags returned by VIDIOC_QUERY_DV_TIMINGS in the polarities field of the v4l2_bt_timings struct.

0 - active low

1 - active high

2 - not available

vsync_gap_length (RW):

If the incoming video signal does not contain synchronization VSYNC and HSYNC pulses, these must be generated internally in the FPGA to achieve the correct frame ordering. This value indicates, how many “empty” pixels (pixels with deasserted Data Enable signal) are necessary to generate the internal VSYNC pulse.

hsync_gap_length (RW):

If the incoming video signal does not contain synchronization VSYNC and HSYNC pulses, these must be generated internally in the FPGA to achieve the correct frame ordering. This value indicates, how many “empty” pixels (pixels with deasserted Data Enable signal) are necessary to generate the internal HSYNC pulse. The value must be greater than 1 and smaller than vsync_gap_length.

pclk_frequency (R):

Input pixel clock frequency in kHz.

The value is identical to what VIDIOC_QUERY_DV_TIMINGS returns in the pixelclock field of the v4l2_bt_timings struct.

Note: The frequency_range parameter must be set properly first to get a valid frequency here.

hsync_width (R):

Width of the HSYNC signal in PCLK clock ticks.

The value is identical to what VIDIOC_QUERY_DV_TIMINGS returns in the hsync field of the v4l2_bt_timings struct.

vsync_width (R):

Width of the VSYNC signal in PCLK clock ticks.

The value is identical to what VIDIOC_QUERY_DV_TIMINGS returns in the vsync field of the v4l2_bt_timings struct.

hback_porch (R):

Number of PCLK pulses between deassertion of the HSYNC signal and the first valid pixel in the video line (marked by DE=1).

The value is identical to what VIDIOC_QUERY_DV_TIMINGS returns in the hbackporch field of the v4l2_bt_timings struct.

hfront_porch (R):

Number of PCLK pulses between the end of the last valid pixel in the video line (marked by DE=1) and assertion of the HSYNC signal.

The value is identical to what VIDIOC_QUERY_DV_TIMINGS returns in the hfrontporch field of the v4l2_bt_timings struct.

vback_porch (R):

Number of video lines between deassertion of the VSYNC signal and the video line with the first valid pixel (marked by DE=1).

The value is identical to what VIDIOC_QUERY_DV_TIMINGS returns in the vbackporch field of the v4l2_bt_timings struct.

vfront_porch (R):

Number of video lines between the end of the last valid pixel line (marked by DE=1) and assertion of the VSYNC signal.

The value is identical to what VIDIOC_QUERY_DV_TIMINGS returns in the vfrontporch field of the v4l2_bt_timings struct.

frequency_range (RW)

PLL frequency range of the OLDI input clock generator. The PLL frequency is derived from the Pixel Clock Frequency (PCLK) and is equal to PCLK if oldi_lane_width is set to “single” and PCLK/2 if oldi_lane_width is set to “dual”.

0 - PLL < 50MHz (default)

1 - PLL >= 50MHz

Note: This parameter can not be changed while the input v4l2 device is open.

7.10.1.3. Common FPDL3/GMSL output parameters

output_id (R):

Output number ID, zero based.

video_source (RW):

Output video source. If set to 0 or 1, the source is the corresponding card input and the v4l2 output devices are disabled. If set to 2 or 3, the source is the corresponding v4l2 video output device. The default is the corresponding v4l2 output, i.e. 2 for OUT1 and 3 for OUT2.

0 - input 0

1 - input 1

2 - v4l2 output 0

3 - v4l2 output 1

Note: This parameter can not be changed while ANY of the input/output v4l2 devices is open.

display_width (RW):

Display width. There is no autodetection of the connected display, so the proper value must be set before the start of streaming. The default width is 1280.

Note: This parameter can not be changed while the output v4l2 device is open.

display_height (RW):

Display height. There is no autodetection of the connected display, so the proper value must be set before the start of streaming. The default height is 640.

Note: This parameter can not be changed while the output v4l2 device is open.

frame_rate (RW):

Output video signal frame rate limit in frames per second. Due to the limited output pixel clock steps, the card can not always generate a frame rate perfectly matching the value required by the connected display. Using this parameter one can limit the frame rate by “crippling” the signal so that the lines are not equal (the porches of the last line differ) but the signal appears like having the exact frame rate to the connected display. The default frame rate limit is 60Hz.

hsync_polarity (RW):

HSYNC signal polarity.

0 - active low (default)

1 - active high

vsync_polarity (RW):

VSYNC signal polarity.

0 - active low (default)

1 - active high

de_polarity (RW):

DE signal polarity.

0 - active low

1 - active high (default)

pclk_frequency (RW):

Output pixel clock frequency. Allowed values are between 25000-190000(kHz) and there is a non-linear stepping between two consecutive allowed frequencies. The driver finds the nearest allowed frequency to the given value and sets it. When reading this property, you get the exact frequency set by the driver. The default frequency is 61150kHz.

Note: This parameter can not be changed while the output v4l2 device is open.

hsync_width (RW):

Width of the HSYNC signal in pixels. The default value is 40.

vsync_width (RW):

Width of the VSYNC signal in video lines. The default value is 20.

hback_porch (RW):

Number of PCLK pulses between deassertion of the HSYNC signal and the first valid pixel in the video line (marked by DE=1). The default value is 50.

hfront_porch (RW):

Number of PCLK pulses between the end of the last valid pixel in the video line (marked by DE=1) and assertion of the HSYNC signal. The default value is 50.

vback_porch (RW):

Number of video lines between deassertion of the VSYNC signal and the video line with the first valid pixel (marked by DE=1). The default value is 31.

vfront_porch (RW):

Number of video lines between the end of the last valid pixel line (marked by DE=1) and assertion of the VSYNC signal. The default value is 30.

7.10.1.4. FPDL3 specific input parameters

fpdl3_input_width (RW):

Number of deserializer input lines.

0 - auto (default)

1 - single

2 - dual

7.10.1.5. FPDL3 specific output parameters

fpdl3_output_width (RW):

Number of serializer output lines.

0 - auto (default)

1 - single

2 - dual

7.10.1.6. GMSL specific input parameters

gmsl_mode (RW):

GMSL speed mode.

0 - 12Gb/s (default)

1 - 6Gb/s

2 - 3Gb/s

3 - 1.5Gb/s

gmsl_stream_id (RW):

The GMSL multi-stream contains up to four video streams. This parameter selects which stream is captured by the video input. The value is the zero-based index of the stream. The default stream id is 0.

Note: This parameter can not be changed while the input v4l2 device is open.

gmsl_fec (RW):

GMSL Forward Error Correction (FEC).

0 - disabled

1 - enabled (default)

7.10.2. MTD partitions

The mgb4 driver creates a MTD device with two partitions:

• mgb4-fw.X - FPGA firmware.

• mgb4-data.X - Factory settings, e.g. card serial number.

The mgb4-fw partition is writable and is used for FW updates, mgb4-data is read-only. The X attached to the partition name represents the card number. Depending on the CONFIG_MTD_PARTITIONED_MASTER kernel configuration, you may also have a third partition named mgb4-flash available in the system. This partition represents the whole, unpartitioned, card’s FLASH memory and one should not fiddle with it...

7.10.3. IIO (triggers)

The mgb4 driver creates an Industrial I/O (IIO) device that provides trigger and signal level status capability. The following scan elements are available:

activity:

The trigger levels and pending status.

bit 1 - trigger 1 pending

bit 2 - trigger 2 pending

bit 5 - trigger 1 level

bit 6 - trigger 2 level

timestamp:

The trigger event timestamp.

The iio device can operate either in “raw” mode where you can fetch the signal levels (activity bits 5 and 6) using sysfs access or in triggered buffer mode. In the triggered buffer mode you can follow the signal level changes (activity bits 1 and 2) using the iio device in /dev. If you enable the timestamps, you will also get the exact trigger event time that can be matched to a video frame (every mgb4 video frame has a timestamp with the same clock source).

Note: although the activity sample always contains all the status bits, it makes no sense to get the pending bits in raw mode or the level bits in the triggered buffer mode - the values do not represent valid data in such case.