[PATCH 17/19] usb: xhci: Implement xhci_handshake_check_state() helper

[Mathias Nyman <mathias.nyman@linux.intel.com>]

From: Udipto Goswami <quic_ugoswami@quicinc.com>

In some situations where xhci removal happens parallel to xhci_handshake,
we encounter a scenario where the xhci_handshake can't succeed, and it
polls until timeout.

If xhci_handshake runs until timeout it can on some platforms result in
a long wait which might lead to a watchdog timeout.

Add a helper that checks xhci status during the handshake, and exits if
set state is entered. Use this helper in places where xhci_handshake is
called unlocked and has a long timeout. For example  xhci command timeout
and xhci reset.

[commit message and code comment rewording -Mathias]

Signed-off-by: Udipto Goswami <quic_ugoswami@quicinc.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
 drivers/usb/host/xhci-ring.c |  5 +++--
 drivers/usb/host/xhci.c      | 26 +++++++++++++++++++++++++-
 drivers/usb/host/xhci.h      |  2 ++
 3 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 73057f01e4aa..f3b5e6345858 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -450,8 +450,9 @@ static int xhci_abort_cmd_ring(struct xhci_hcd *xhci, unsigned long flags)
 	 * In the future we should distinguish between -ENODEV and -ETIMEDOUT
 	 * and try to recover a -ETIMEDOUT with a host controller reset.
 	 */
-	ret = xhci_handshake(&xhci->op_regs->cmd_ring,
-			CMD_RING_RUNNING, 0, 5 * 1000 * 1000);
+	ret = xhci_handshake_check_state(xhci, &xhci->op_regs->cmd_ring,
+			CMD_RING_RUNNING, 0, 5 * 1000 * 1000,
+			XHCI_STATE_REMOVING);
 	if (ret < 0) {
 		xhci_err(xhci, "Abort failed to stop command ring: %d\n", ret);
 		xhci_halt(xhci);
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 68920cb96044..119cbe2a3d65 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -81,6 +81,29 @@ int xhci_handshake(void __iomem *ptr, u32 mask, u32 done, u64 timeout_us)
 	return ret;
 }
 
+/*
+ * xhci_handshake_check_state - same as xhci_handshake but takes an additional
+ * exit_state parameter, and bails out with an error immediately when xhc_state
+ * has exit_state flag set.
+ */
+int xhci_handshake_check_state(struct xhci_hcd *xhci, void __iomem *ptr,
+		u32 mask, u32 done, int usec, unsigned int exit_state)
+{
+	u32	result;
+	int	ret;
+
+	ret = readl_poll_timeout_atomic(ptr, result,
+				(result & mask) == done ||
+				result == U32_MAX ||
+				xhci->xhc_state & exit_state,
+				1, usec);
+
+	if (result == U32_MAX || xhci->xhc_state & exit_state)
+		return -ENODEV;
+
+	return ret;
+}
+
 /*
  * Disable interrupts and begin the xHCI halting process.
  */
@@ -201,7 +224,8 @@ int xhci_reset(struct xhci_hcd *xhci, u64 timeout_us)
 	if (xhci->quirks & XHCI_INTEL_HOST)
 		udelay(1000);
 
-	ret = xhci_handshake(&xhci->op_regs->command, CMD_RESET, 0, timeout_us);
+	ret = xhci_handshake_check_state(xhci, &xhci->op_regs->command,
+				CMD_RESET, 0, timeout_us, XHCI_STATE_REMOVING);
 	if (ret)
 		return ret;
 
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 813d55468c00..5768ce804caa 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -2084,6 +2084,8 @@ void xhci_free_container_ctx(struct xhci_hcd *xhci,
 /* xHCI host controller glue */
 typedef void (*xhci_get_quirks_t)(struct device *, struct xhci_hcd *);
 int xhci_handshake(void __iomem *ptr, u32 mask, u32 done, u64 timeout_us);
+int xhci_handshake_check_state(struct xhci_hcd *xhci, void __iomem *ptr,
+		u32 mask, u32 done, int usec, unsigned int exit_state);
 void xhci_quiesce(struct xhci_hcd *xhci);
 int xhci_halt(struct xhci_hcd *xhci);
 int xhci_start(struct xhci_hcd *xhci);
-- 
2.25.1