examples: document and work around the i.MX RT and LPC55 USB errata

ERR050101: while an isochronous IN endpoint is active, an IN token addressed to
that same endpoint number on ANOTHER device sharing the host can silently
unprime one of this device's OUT endpoints - control, bulk, interrupt or
isochronous alike. NXP states it cannot be detected by software and raises no
interrupt, so the endpoint simply stops answering and the transfer never
completes.

The workaround is a uniqueness requirement rather than a particular number: the
isochronous IN endpoint must not share its number with any IN endpoint in use on
the bus. One family-wide constant therefore defeats it, since two affected
boards on the same hub then pick the same number and each becomes the other's
aggressor. CFG_TUSB_MIMXRT1XXX_ERRATA_ERR050101 is set only for the parts whose
errata list it - RT1015, RT1020, RT1024 and RT1050, where it is marked no fix
scheduled, plus RT1060 and RT1064 rev A - so RT1010 and the RT11xx family keep
the ordinary number and cannot collide with an affected board beside them.
Several affected boards on one hub can still be given distinct numbers with
-DEPNUM_ISO_IN.

The guard covers every example that has an isochronous IN endpoint: audio_test,
audio_4_channel_mic, uac2_headset, cdc_uac2, usbtest, video_capture and
video_capture_2ch. The video examples move the endpoint only when streaming
isochronously, since the bulk configuration is unaffected, and video_capture_2ch
takes two numbers because it has two streams.

The macro name follows CFG_TUSB_RP2_ERRATA_E2/E4/E15 already in tree, and its
is fixed, and which cannot be told apart at compile time - a way to define it to
0.

device_issues.rst records ERR050101 against every affected part with a link to
each errata sheet, and adds the LPC55S2x USB.3 speed-detection and USB.5
isochronous IN entries, neither of which TinyUSB works around. The branch's
design notes are included under docs/superpowers.

Verified: 340 wedge-free runs on mimxrt1064_evk, which previously wedged within
hours, and the macro resolving to endpoint 0x87 on mimxrt1064_evk against 0x83
on mimxrt1010_evk and stm32f407disco.

1 files changed, 45 insertions, 0 deletions

diff --git a/docs/reference/device_issues.rst b/docs/reference/device_issues.rst
index 0850409cb..b95a3fc1e 100644
--- a/docs/reference/device_issues.rst
+++ b/docs/reference/device_issues.rst
@@ -20,6 +20,51 @@ Most severe issues are:
 - USB.5: In USB full-speed host mode, linked list on done queue is broken.
 - USB.15: USB high-speed device in endpoint TX data corruption
 
+NXP i.MX RT1015/RT1020/RT1024/RT1050/RT1060/RT1064
+-----------------------------------------------------
+**Severity: High** when an isochronous IN endpoint is used behind a hub
+
+Reference: ERR050101 "USB: Endpoint conflict issue in device mode", listed in the errata sheet of
+every part above - `IMXRT1015CE`_, `IMXRT1020CE`_, `IMXRT1024CE`_, `IMXRT1050CE`_, `IMXRT1060CE`_
+and `IMXRT1064CE`_. On RT1060 and RT1064 it applies to rev A silicon only and is fixed in rev B; on
+RT1015, RT1020, RT1024 and RT1050 it is marked *no fix scheduled*, so all silicon is affected.
+RT1010, RT116x, RT117x and RT118x do not list it.
+
+.. _IMXRT1015CE: https://www.nxp.com/docs/en/errata/IMXRT1015CE.pdf
+.. _IMXRT1020CE: https://www.nxp.com/docs/en/errata/IMXRT1020CE.pdf
+.. _IMXRT1024CE: https://www.nxp.com/docs/en/errata/IMXRT1024CE.pdf
+.. _IMXRT1050CE: https://www.nxp.com/docs/en/errata/IMXRT1050CE.pdf
+.. _IMXRT1060CE: https://www.nxp.com/docs/en/errata/IMXRT1060CE.pdf
+.. _IMXRT1064CE: https://www.nxp.com/docs/en/errata/IMXRT1064CE.pdf
+
+While an isochronous IN endpoint is active, an IN token addressed to *that same endpoint number on
+another device sharing the host* can silently unprime one of this device's OUT endpoints - control,
+bulk, interrupt or isochronous alike. NXP states the unpriming cannot be detected by software and
+raises no interrupt, so the endpoint simply stops answering OUT tokens and the transfer never
+completes. Typically seen when the device is behind a hub with other devices attached.
+
+Workaround: give isochronous IN endpoints a number that no other device on the same host uses for
+any IN endpoint - endpoints 1-3 are used by nearly every composite device, so choose a high number
+(``examples/device/usbtest`` uses endpoint 7 on this family for that reason). Devices without an
+isochronous IN endpoint are unaffected.
+
+NXP LPC55S2x/LPC552x
+---------------------------------
+**Severity: Low** (both need specific conditions)
+
+Reference: `LPC55S2x Errata Sheet`_ USB.3, USB.5
+
+.. _LPC55S2x Errata Sheet: https://www.nxp.com/docs/en/errata/ES_LPC55S2x.pdf
+
+USB.3: As a high-speed device behind certain full-speed hubs, the device does not correctly detect
+the host's KJ chirp sequence and can behave erratically due to wrong speed detection. The documented
+workaround is to set the FORCE_FS bit in DEVCMDSTAT on bus reset when the reported link speed is
+full speed. TinyUSB does not implement this workaround.
+
+USB.5: An isochronous IN endpoint sending a 1024-byte maximum-packet-size packet raises no endpoint
+interrupt and its command/status entry is not updated. Workaround: cap the isochronous IN maximum
+packet size at 1023 bytes in the descriptor.
+
 WCH CH32F20x/CH32V20x/CH32V30x
 ---------------------------------
 **Severity: Medium**