BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//CERN//INDICO//EN
BEGIN:VEVENT
SUMMARY:Navigating the Tunnel : DisplayPort over USB4/TBT
DTSTART;VALUE=DATE-TIME:20260930T203500Z
DTEND;VALUE=DATE-TIME:20260930T204000Z
DTSTAMP;VALUE=DATE-TIME:20260904T154114Z
UID:indico-contribution-567@indico.freedesktop.org
DESCRIPTION:Speakers: Kunal Joshi (intel)\nA familiar failure motivates th
 is talk: two high-resolution displays on one USB4/Thunderbolt dock\, each 
 working alone but not together\, because nothing arbitrates the shared lin
 k.\n\nA DisplayPort monitor on such a dock looks like an ordinary connecto
 r to userspace\, but in the kernel the work is split across two subsystems
  that never call each other. The graphics driver (i915/xe plus the DRM DP 
 tunnel helpers) owns the DP source\, mode validation\, and atomic state. T
 he USB4/Thunderbolt connection manager (drivers/thunderbolt\, or controlle
 r firmware) owns the physical link and the bandwidth of every tunnel (i.e.
  DisplayPort\, PCIe\, USB3) sharing it. The two domains coordinate only th
 rough the DisplayPort Bandwidth Allocation protocol: a small set of DPCD r
 egisters carried over AUX.\n\nFrom that starting point the full bandwidth 
 lifecycle unfolds: how available bandwidth is estimated\, how a stream's r
 equirement is computed\, how the group budget is enforced during the atomi
 c check\, how the request is issued at commit and answered by the connecti
 on manager\, and how the state is updated at runtime.\n\n###Overview\n![Ov
 erview][1]\n\n###Outline\n1. **DP over USB4/Thunderbolt\, and the subsyste
 m split**\n   - What DP tunneling is\, and how it appears to userspace.\n 
   - The split of responsibility: DRM/KMS vs. `drivers/thunderbolt`.\n2. **
 The Bandwidth Allocation protocol**\n   - The DPCD register interface and 
 how a request reaches the connection manager.\n   - How the DRM DP tunnel 
 helpers bridge the two domains.\n3. **Case study: two displays on one dock
 **\n   - Walkthrough of a dock bandwidth exhaustion scenario.\n   - Estima
 tion\, requests\, and atomic-state representation in `i915`/`xe`.\n4. **Ho
 tplug**\n   - Dynamic recalculation on hotplug and state changes.\n5. **Fu
 ture work and upstreaming**\n   - Panel Replay bandwidth optimization.\n  
  - Asymmetric USB4 links and UHBR.\n   - Validation strategies.\n\nUpstrea
 m contributor : Imre Deak \n\n  [1]: https://github.com/KunalJoshi95/xdc/b
 lob/main/abstract.svg "Overview"\n\nhttps://indico.freedesktop.org/event/1
 2/contributions/567/
LOCATION:
URL:https://indico.freedesktop.org/event/12/contributions/567/
END:VEVENT
END:VCALENDAR