From: Radhey Shyam Pandey radhey.shyam.pandey@amd.com
[ Upstream commit 70627bf82e36e61c40c3315e1206e4ea4c02e668 ]
Adds a shutdown callback to ensure that the XHCI stack is properly shutdown in reboot/shutdown path.
In kexec flow, kernel_restart_prepare() performs actions necessary to prepare the system for a restart and invokes device_shutdown. To ensure proper shutdown attach the dwc3 shutdown implementation which mirrors the remove method.
$ kexec -e
<snip> xhci-hcd xhci-hcd.0.auto: remove, state 1 usb usb1: USB disconnect, device number 1 usb 1-1: USB disconnect, device number 6 xhci-hcd xhci-hcd.0.auto: USB bus 1 deregistered kexec_core: Starting new kernel
Signed-off-by: Radhey Shyam Pandey radhey.shyam.pandey@amd.com Acked-by: Thinh Nguyen Thinh.Nguyen@synopsys.com Link: https://lore.kernel.org/r/1748977771-714153-1-git-send-email-radhey.shyam.pa... 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 should be backported to stable kernel trees. Here's my detailed analysis:
## Analysis of the Commit
### 1. **Bug Fix Nature** This commit fixes a real bug where the USB XHCI stack is not properly shut down during kexec operations. The commit message explicitly shows the issue - when `kexec -e` is executed, the XHCI controller is removed but without a proper shutdown sequence, which can lead to: - Memory corruption if the controller continues DMA operations - System instability during kexec transitions - Potential crashes after kexec
### 2. **Simple and Contained Fix** The code change is minimal and low-risk: ```diff + .shutdown = dwc3_xlnx_remove, ``` It simply reuses the existing `dwc3_xlnx_remove` function as the shutdown callback. This is a common pattern in kernel drivers.
### 3. **Follows Established Pattern** My analysis shows this follows an established pattern in the dwc3 driver family: - `dwc3-of-simple.c` uses its remove function for shutdown - `dwc3-rtk.c` has a dedicated shutdown function that calls similar cleanup - The recent Tegra XUSB commit (3a3be3a1ebf0) added a shutdown callback for similar reasons (preventing SMMU-related crashes)
### 4. **Clear Side Effects** The `dwc3_xlnx_remove` function performs standard cleanup: - Depopulates child devices (`of_platform_depopulate`) - Disables and unprepares clocks - Manages runtime PM state
These are all safe operations for shutdown context.
### 5. **Meets Stable Criteria** - **Fixes a real bug**: Prevents potential system instability during kexec - **Small change**: Single line addition - **Low risk**: Reuses existing, tested code path - **No new features**: Pure bug fix - **Clear benefit**: Improves system reliability during reboot/kexec operations
### 6. **Similar Issues in Other Drivers** The pattern of missing shutdown callbacks causing issues during kexec/reboot is well-documented in the kernel, particularly for devices that perform DMA operations.
The fix ensures proper hardware shutdown sequence during system reboot/shutdown, preventing the USB controller from accessing memory after the system has started transitioning to a new kernel or shutting down. This is especially important for systems using kexec for fast reboots or crash dump collection.
drivers/usb/dwc3/dwc3-xilinx.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/drivers/usb/dwc3/dwc3-xilinx.c b/drivers/usb/dwc3/dwc3-xilinx.c index 4ca7f6240d07..09c3c5c226ab 100644 --- a/drivers/usb/dwc3/dwc3-xilinx.c +++ b/drivers/usb/dwc3/dwc3-xilinx.c @@ -422,6 +422,7 @@ static const struct dev_pm_ops dwc3_xlnx_dev_pm_ops = { static struct platform_driver dwc3_xlnx_driver = { .probe = dwc3_xlnx_probe, .remove = dwc3_xlnx_remove, + .shutdown = dwc3_xlnx_remove, .driver = { .name = "dwc3-xilinx", .of_match_table = dwc3_xlnx_of_match,