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Artem Mygaiev edited this page May 12, 2024 · 2 revisions

Welcome to the fl2000 Linux DRM driver wiki!

Driver is already working, see demo video 1 and demo video 2

FL2000DX

The FL2000DX is Fresco Logic’s USB 3.0 Display device controller. It integrates Fresco Logic’s display transfer engine, USB 3.0 device controller, USB 3.0 transceiver, and a VGA (D-Sub) DAC. Fresco Logic’s display transfer engine is designed with Fresco Logic’s proprietary architecture and processes the video stream optimally for USB 3.0 bandwidth. The high performance video DAC provides clear and crisp display quality, and supports full HD (1920×1080) resolution. The integrated USB 3.0 device controller and transceiver were developed in conjunction with the de-facto standard Fresco USB 3.0 host controllers, which ensures the best performance and compatibility.

IT66121FN

The IT66121 is a high-performance and low-power single channel HDMI transmitter, fully compliant with HDMI 1.3a, HDCP 1.2 and backward compatible to DVI 1.0 specifications. IT66121 also provide the HDMI1.4 3D feature, which enables direct 3D displays through an HDMI link. The IT66121 serves to provide the most cost-effective HDMI solution for DTV-ready consumer electronics such as set-top boxes, DVD players and A/V receivers, as well as DTV-enriched PC products such as notebooks and desktops, without compromising the performance. Its backward compatibility to DVI standard allows connectivity to myriad video displays such as LCD and CRT monitors, in addition to the ever-so-flourishing Flat Panel TVs.

Implementation

Driver structure

All registers (both FL2000 and IT66121) access is implemented via regmaps. It is assumed that FL2000DX outputs DPI interface (kind of "crtc" output, not "encoder") that is connected to HDMI or other transciever. USB Bulk Streams are not supported by FL2000DX, so implementation will simly use Bulk endpoint.

See debug section and analysis section for more details on development.

Endpoints addresses HW bug

Recent kernels have a fix that checks duplication of USB endpoint numbers across interfaces which is an issue due to HW design bug: it uses same endpoint #1 across interfaces 1 and 2, which is not allowed by USB specification:endpoint addresses can be shared only between alternate settings, not between interfaces. Kernel log with issue looks like this:

new SuperSpeed Gen 1 USB device number 2 using xhci_hcd
config 1 interface 1 altsetting 0 has a duplicate endpoint with address 0x81, skipping
config 1 interface 1 altsetting 0 has a duplicate endpoint with address 0x1, skipping
config 1 interface 1 altsetting 1 has a duplicate endpoint with address 0x81, skipping
config 1 interface 1 altsetting 1 has a duplicate endpoint with address 0x1, skipping
config 1 interface 1 altsetting 2 has a duplicate endpoint with address 0x81, skipping
config 1 interface 1 altsetting 2 has a duplicate endpoint with address 0x1, skipping
config 1 interface 1 altsetting 3 has a duplicate endpoint with address 0x81, skipping
config 1 interface 1 altsetting 3 has a duplicate endpoint with address 0x1, skipping
config 1 interface 1 altsetting 4 has a duplicate endpoint with address 0x81, skipping
config 1 interface 1 altsetting 4 has a duplicate endpoint with address 0x1, skipping
config 1 interface 1 altsetting 5 has a duplicate endpoint with address 0x81, skipping
config 1 interface 1 altsetting 5 has a duplicate endpoint with address 0x1, skipping
config 1 interface 1 altsetting 6 has a duplicate endpoint with address 0x81, skipping
config 1 interface 1 altsetting 6 has a duplicate endpoint with address 0x1, skipping

In order to workaround this same as original driver we use default altsetting (#0) of streaming interface (#1) with bulk transfers.

How to use

IMPORTANT! As it is seen from the original driver sources FL2000 does not properly support USB3 U1/U2 LPM. While the dongle was working properly woth desktop Linux machine, on the laptop with Linux the dongle had issues because USB hub was setting U1/U2 timers despite LPM configuration was disabled in the driver. Issues observed were: all interrupt URBs were not delivered, sometimes control URBs were not delivered. This can probably be fixed using Linux USB device quirks, e.g. with kernel boot param:
quirks=1D5C:2000:USB_QUIRK_NO_LPM

Limitations (not implemented)

  • D-sub
  • HDMI CEC
  • HDMI Audio
  • HDCP
  • USB 2.0
  • Dongle onboard SPI EEPROM access via USB Mass Storage

Known issues

  • Connecting more than one dongle to the same USB bus may not work
  • Non big-endian hosts (e.g. little endian) may not work
  • 32-bit hosts may not work

Upstreaming

Considering, no firm decision yet. Current design uses unsafe components linking and non-standard I2C device class for autodetection, this has to be addresed prior to upstreaming

Sources

Documentation

Not shared here due to NDAs, Copyrights, etc.

  • FL2000 MP Memory Mapped Address Space Registers
  • IT66121FN Datasheet v1.02
  • IT66121 Programming Guide v1.05
  • IT66121 Register List Release V1.0
  • AV BDP v1.0
  • CEA-861-D
  • VESA-EEDID-A2

Notes

  • VGA (D-Sub) DAC output of FL2000DX can be implemented as a DRM bridge (dumb_vga_dac)
  • For registration of sibling I2C devices of IT66121 (CEC, ...) i2c_new_dummy() function may be used

TODO

See the project's Kanban board for the latest bugs, features and so on.

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