On Thu, May 15, 2025, Roy Luo wrote:
Commit 6ccb83d6c497 ("usb: xhci: Implement xhci_handshake_check_state() helper") introduced an optimization to xhci_reset() during xhci removal, allowing it to bail out early without waiting for the reset to complete.
This behavior can cause issues on SNPS DWC3 USB controller with dual-role capability. When the DWC3 controller exits host mode and removes xhci while a reset is still in progress, and then tries to configure its hardware for device mode, the ongoing reset leads to register access issues; specifically, all register reads returns 0. These issues extend beyond the xhci register space (which is expected during a reset) and affect the entire DWC3 IP block, causing the DWC3 device mode to malfunction.
To address this, introduce the `XHCI_FULL_RESET_ON_REMOVE` quirk. When this quirk is set, xhci_reset() always completes its reset handshake, ensuring the controller is in a fully reset state before proceeding.
Cc: stable@vger.kernel.org Fixes: 6ccb83d6c497 ("usb: xhci: Implement xhci_handshake_check_state() helper") Signed-off-by: Roy Luo royluo@google.com
drivers/usb/host/xhci-plat.c | 3 +++ drivers/usb/host/xhci.c | 8 +++++++- drivers/usb/host/xhci.h | 1 + 3 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c index 3155e3a842da..19c5c26a8e63 100644 --- a/drivers/usb/host/xhci-plat.c +++ b/drivers/usb/host/xhci-plat.c @@ -265,6 +265,9 @@ int xhci_plat_probe(struct platform_device *pdev, struct device *sysdev, const s if (device_property_read_bool(tmpdev, "xhci-skip-phy-init-quirk")) xhci->quirks |= XHCI_SKIP_PHY_INIT;
if (device_property_read_bool(tmpdev, "xhci-full-reset-on-remove-quirk"))xhci->quirks |= XHCI_FULL_RESET_ON_REMOVE;- device_property_read_u32(tmpdev, "imod-interval-ns", &xhci->imod_interval); }
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c index 90eb491267b5..4f091d618c01 100644 --- a/drivers/usb/host/xhci.c +++ b/drivers/usb/host/xhci.c @@ -198,6 +198,7 @@ int xhci_reset(struct xhci_hcd *xhci, u64 timeout_us) u32 command; u32 state; int ret;
- unsigned int exit_state;
state = readl(&xhci->op_regs->status); @@ -226,8 +227,13 @@ int xhci_reset(struct xhci_hcd *xhci, u64 timeout_us) if (xhci->quirks & XHCI_INTEL_HOST) udelay(1000);
- if (xhci->quirks & XHCI_FULL_RESET_ON_REMOVE)
exit_state = 0;
There's no state 0. Checking against that is odd. Couldn't we just use xhci_handshake() equivalent instead?
In any case, this is basically a revert of this change: 6ccb83d6c497 ("usb: xhci: Implement xhci_handshake_check_state() helper")
Can't we just revert or fix the above patch that causes a regression?
Thanks, Thinh
- else
exit_state = XHCI_STATE_REMOVING;- ret = xhci_handshake_check_state(xhci, &xhci->op_regs->command,
CMD_RESET, 0, timeout_us, XHCI_STATE_REMOVING);
CMD_RESET, 0, timeout_us, exit_state);diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h index 242ab9fbc8ae..ac65af788298 100644 --- a/drivers/usb/host/xhci.h +++ b/drivers/usb/host/xhci.h @@ -1637,6 +1637,7 @@ struct xhci_hcd { #define XHCI_WRITE_64_HI_LO BIT_ULL(47) #define XHCI_CDNS_SCTX_QUIRK BIT_ULL(48) #define XHCI_ETRON_HOST BIT_ULL(49) +#define XHCI_FULL_RESET_ON_REMOVE BIT_ULL(50) unsigned int num_active_eps; unsigned int limit_active_eps; -- 2.49.0.1112.g889b7c5bd8-goog