[PATCH v2 1/1] usb: xhci: clear EINT bit in status correctly

[Lu Baolu <baolu.lu@linux.intel.com>]

EINT(Event Interrupt) is a write-1-to-clear type of bit in xhci
status register. It should be cleared by writing a 1. Writing 0
to this bit has no effect.

Xhci driver tries to clear this bit by writing 0 to it. This is
not the right way to go. This patch corrects this by reading the
register first, then clearing all RO/RW1C/RsvZ bits and setting
the clearing bit, and writing back the new value at last.

Xhci spec requires that software that uses EINT shall clear it
prior to clearing any IP flags in section 5.4.2. This is the
reason why this patch is CC'ed stable as well.

Cc: <stable@vger.kernel.org> # v3.14+
Cc: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
Change log:
v1->v2:
 - Fixed a warning reported by 0-day kbuild robot.

 drivers/usb/host/xhci.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 1cd5641..bb08c6b 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -721,7 +721,7 @@ void xhci_stop(struct usb_hcd *hcd)
 	xhci_dbg_trace(xhci, trace_xhci_dbg_init,
 			"// Disabling event ring interrupts");
 	temp = readl(&xhci->op_regs->status);
-	writel(temp & ~STS_EINT, &xhci->op_regs->status);
+	writel((temp & ~0x1fff) | STS_EINT, &xhci->op_regs->status);
 	temp = readl(&xhci->ir_set->irq_pending);
 	writel(ER_IRQ_DISABLE(temp), &xhci->ir_set->irq_pending);
 	xhci_print_ir_set(xhci, 0);
@@ -1054,7 +1054,7 @@ int xhci_resume(struct xhci_hcd *xhci, bool hibernated)
 
 		xhci_dbg(xhci, "// Disabling event ring interrupts\n");
 		temp = readl(&xhci->op_regs->status);
-		writel(temp & ~STS_EINT, &xhci->op_regs->status);
+		writel((temp & ~0x1fff) | STS_EINT, &xhci->op_regs->status);
 		temp = readl(&xhci->ir_set->irq_pending);
 		writel(ER_IRQ_DISABLE(temp), &xhci->ir_set->irq_pending);
 		xhci_print_ir_set(xhci, 0);
-- 
2.1.4