+ /* For T4 we don't have a shadow copy of the Mailbox Control register.
+ * And since reading that real register causes a side effect of
+ * granting ownership, we're best of simply not reading it at all.
+ */
+ if (is_t4(adap->params.chip)) {
+ i = 4; /* index of "<unread>" */
+ } else {
+ unsigned int ctrl_reg = CIM_PF_MAILBOX_CTRL_SHADOW_COPY_A;
+ void __iomem *ctrl = adap->regs + PF_REG(mbox, ctrl_reg);
+
+ i = MBOWNER_G(readl(ctrl));
+ }
+