Public bug reported:
[Impact]
MT7925 Bluetooth on Dell systems fails to enumerate at boot when the
BT_RST GPIO is stuck low. The device never comes up and Bluetooth is
unavailable. The only recovery is a full mechanical power-off (G3 cycle).
Error log:
[ 6.813942] usb 3-10: device descriptor read/64, error -110
[ 22.685978] usb 3-10: device descriptor read/64, error -110
[ 28.317963] usb 3-10: device descriptor read/64, error -110
[ 44.189949] usb 3-10: device descriptor read/64, error -110
[ 44.189960] usb usb3-port10: unable to enumerate USB device
Warm reboots and S5 sleep do not clear the stuck GPIO state. Hits 100%
on affected hardware once the GPIO is stuck.
[Fix]
Add usb_acpi_port_prr_reset() to drivers/usb/core/usb-acpi.c. When a
USB port has an ACPI _PRR method, the function calls _RST on the
returned power resource to toggle the hardware reset line.
Wire it into hub_port_connect() during the mid-retry VBUS power-cycle:
call _PRR._RST while VBUS is off so the GPIO pulse completes before the
device gets power. After VBUS comes back on, sleep 100 ms (per USB 2.0
spec ยง7.1.7.3 Fig. 7-29) when _RST succeeded, because
hub_power_on_good_delay() has no minimum floor and can return as little
as 20 ms on xHCI root hubs.
Not yet upstream. Patch submitted for upstream review.
[Test Plan]
Trigger the stuck-GPIO condition (G3 cycle on affected Dell hardware to
put the system in a normal state, then warm reboot to reproduce).
Without patch:
- dmesg shows repeated "device descriptor read/64, error -110"
- Bluetooth unavailable; recovery requires G3 cycle
With patch:
- dmesg shows "attempt power cycle" followed by successful enumeration
- Bluetooth comes up without any manual intervention
Expected dmesg with patch:
[ 44.294065] usb usb3-port10: attempt power cycle
[ 44.872709] usb 3-10: new high-speed USB device number 6 using xhci_hcd
[ 44.888293] usb 3-10: New USB device found, idVendor=0489, idProduct=e139,
bcdDevice= 1.00
[ 44.888318] usb 3-10: Manufacturer: MediaTek Inc.
[Where problems could occur]
Could affect USB hub port handling in drivers/usb/core/hub.c and
usb-acpi.c.
usb_acpi_port_prr_reset() is a no-op on ports with no ACPI _PRR method,
so non-affected hardware should be unaffected. If the ACPI method
evaluation returns an unexpected object type or the _RST call hangs, the
hub_port_connect() retry loop could stall or log spurious errors.
The 100 ms sleep is conditional on _RST succeeding (prr_reset == 0), so
it does not add latency to ports without _PRR.
** Affects: hwe-next
Importance: Undecided
Status: New
** Affects: linux (Ubuntu)
Importance: Undecided
Assignee: AceLan Kao (acelankao)
Status: In Progress
** Affects: linux-oem-6.17 (Ubuntu)
Importance: Undecided
Status: Invalid
** Affects: linux (Ubuntu Noble)
Importance: Undecided
Status: Invalid
** Affects: linux-oem-6.17 (Ubuntu Noble)
Importance: Undecided
Assignee: AceLan Kao (acelankao)
Status: In Progress
** Affects: linux (Ubuntu Questing)
Importance: Undecided
Assignee: AceLan Kao (acelankao)
Status: In Progress
** Affects: linux-oem-6.17 (Ubuntu Questing)
Importance: Undecided
Status: Invalid
** Affects: linux (Ubuntu Resolute)
Importance: Undecided
Assignee: AceLan Kao (acelankao)
Status: In Progress
** Affects: linux-oem-6.17 (Ubuntu Resolute)
Importance: Undecided
Status: Invalid
** Tags: jira-somerville-4265 oem-priority somerville
** Also affects: linux-oem-6.17 (Ubuntu)
Importance: Undecided
Status: New
** Tags added: jira-somerville-4265 oem-priority somerville
** Also affects: linux (Ubuntu Questing)
Importance: Undecided
Status: New
** Also affects: linux-oem-6.17 (Ubuntu Questing)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Resolute)
Importance: Undecided
Status: New
** Also affects: linux-oem-6.17 (Ubuntu Resolute)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Noble)
Importance: Undecided
Status: New
** Also affects: linux-oem-6.17 (Ubuntu Noble)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu Noble)
Status: New => Invalid
** Changed in: linux (Ubuntu Questing)
Status: New => In Progress
** Changed in: linux (Ubuntu Resolute)
Status: New => In Progress
** Changed in: linux-oem-6.17 (Ubuntu Noble)
Status: New => In Progress
** Changed in: linux-oem-6.17 (Ubuntu Questing)
Status: New => Invalid
** Changed in: linux (Ubuntu Questing)
Assignee: (unassigned) => AceLan Kao (acelankao)
** Changed in: linux-oem-6.17 (Ubuntu Resolute)
Status: New => Invalid
** Changed in: linux (Ubuntu Resolute)
Assignee: (unassigned) => AceLan Kao (acelankao)
** Changed in: linux-oem-6.17 (Ubuntu Noble)
Assignee: (unassigned) => AceLan Kao (acelankao)
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https://bugs.launchpad.net/bugs/2146401
Title:
MT7925 Bluetooth fails to enumerate on Dell systems, requires G3 cycle
to recover
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