From b3f121606014fa4e797c679da8ac63b539e10c92 Mon Sep 17 00:00:00 2001 From: mikkeli Date: Fri, 9 Oct 2026 00:46:33 +0900 Subject: [PATCH] USB report: plug-in with tablet awake costs ~2.2 s No USB-C detach, one gadget reconnect and a fresh DHCP exchange. With sleep ruled out, the hub's PD edges cost ~3.5 s (unplug) and ~2.2 s (plug-in). Co-Authored-By: Claude Opus 5.5 --- docs/impl/reports/USB-TABLET-LINK.md | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/docs/impl/reports/USB-TABLET-LINK.md b/docs/impl/reports/USB-TABLET-LINK.md index 4c3b5dd..aa9897b 100644 --- a/docs/impl/reports/USB-TABLET-LINK.md +++ b/docs/impl/reports/USB-TABLET-LINK.md @@ -117,12 +117,14 @@ Three PD unplug/replug cycles while pinging the tablet every 0.5 s: |---|---|---| | Idle, 3 min window | screen times out | Clean for ~60 s, then pings answered only in brief bursts right at its 30 s DHCP renewals, then silent. **No kernel link events**: USB stayed up throughout | | Video playing, 150 s window | kept awake | 3.1 s outage at the unplug, then **zero loss for 2 min+** | +| Video playing, PD off → **plugged in** (90 s window) | kept awake | No USB-C detach; one gadget reconnect (link down 0.7 s), fresh DHCP, **~2.2 s** to ping replies, then zero loss | - Off charger and idle, Android suspends about 60 s after the screen times out ("keep awake on charge" no longer applies). The USB gadget link stays electrically up, but the tablet only wakes for timers (DHCP renewal every ~30 s). - The earlier "replug silence" was the same thing. Those windows started with the tablet already asleep, so plugging power in woke it, and the 5–8 s was wake-up plus re-creating its USB network. -- So the hub's PD change costs **~3.5 s** (the unplug detach). Everything beyond that came from tablet sleep. +- So with the tablet awake, the hub's PD changes cost **~3.5 s on unplug** (full detach) and **~2.2 s on plug-in** (gadget reconnect only). + Everything beyond that came from tablet sleep. - To the Orin, a sleeping tablet is indistinguishable from a dead link, except by heartbeat. - At ignition, accessory power drops during cranking, so a start is likely to produce both edges back to back (not tested in the car yet).