From: Su Hui suhui@nfschina.com
[ Upstream commit 7919407eca2ef562fa6c98c41cfdf6f6cdd69d92 ]
When encounters some errors like these: xhci_hcd 0000:4a:00.2: xHCI dying or halted, can't queue_command xhci_hcd 0000:4a:00.2: FIXME: allocate a command ring segment usb usb5-port6: couldn't allocate usb_device
It's hard to know whether xhc_state is dying or halted. So it's better to print xhc_state's value which can help locate the resaon of the bug.
Signed-off-by: Su Hui suhui@nfschina.com Link: https://lore.kernel.org/r/20250725060117.1773770-1-suhui@nfschina.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org ---
LLM Generated explanations, may be completely bogus:
**Backport Status: YES**
This commit is suitable for backporting to stable kernel trees for the following reasons:
1. **Enhanced Debugging for Real-World Issues**: The commit improves debugging of USB xHCI host controller failures by printing the actual `xhc_state` value when `queue_command` fails. The commit message shows real error messages users encounter ("xHCI dying or halted, can't queue_command"), demonstrating this is a real-world debugging problem.
2. **Minimal and Safe Change**: The change is extremely small and safe - it only modifies a debug print statement from: ```c xhci_dbg(xhci, "xHCI dying or halted, can't queue_command\n"); ``` to: ```c xhci_dbg(xhci, "xHCI dying or halted, can't queue_command. state: 0x%x\n", xhci->xhc_state); ```
3. **No Functional Changes**: This is a pure diagnostic improvement. It doesn't change any logic, control flow, or data structures. It only adds the state value (0x%x format) to an existing debug message.
4. **Important for Troubleshooting**: The xHCI driver is critical for USB functionality, and when it fails with "dying or halted" states, knowing the exact state helps diagnose whether: - `XHCI_STATE_DYING` (0x1) - controller is dying - `XHCI_STATE_HALTED` (0x2) - controller is halted - Both states (0x3) - controller has both flags set
This distinction is valuable for debugging hardware issues, driver bugs, or system problems.
5. **Zero Risk of Regression**: Adding a parameter to a debug print statement has no risk of introducing regressions. The worst case is the debug message prints the state value.
6. **Follows Stable Rules**: This meets stable kernel criteria as it: - Fixes a real debugging limitation - Is obviously correct - Has been tested (signed-off and accepted by Greg KH) - Is small (single line change) - Doesn't add new features, just improves existing diagnostics
The commit helps system administrators and developers diagnose USB issues more effectively by providing the actual state value rather than just saying "dying or halted", making it a valuable debugging enhancement for stable kernels.
drivers/usb/host/xhci-ring.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c index 94c9c9271658..131e7530ec4a 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -4372,7 +4372,8 @@ static int queue_command(struct xhci_hcd *xhci, struct xhci_command *cmd,
if ((xhci->xhc_state & XHCI_STATE_DYING) || (xhci->xhc_state & XHCI_STATE_HALTED)) { - xhci_dbg(xhci, "xHCI dying or halted, can't queue_command\n"); + xhci_dbg(xhci, "xHCI dying or halted, can't queue_command. state: 0x%x\n", + xhci->xhc_state); return -ESHUTDOWN; }