cxgb4: For T4, don't read the Firmware Mailbox Control register
authorHariprasad Shenai <hariprasad@chelsio.com>
Thu, 1 Oct 2015 08:18:46 +0000 (13:48 +0530)
committerDavid S. Miller <davem@davemloft.net>
Mon, 5 Oct 2015 10:48:40 +0000 (03:48 -0700)
T4 doesn't have the Shadow copy of the register which we can read without
side effect. So don't read mbox control register for T4 adapter

Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
drivers/net/ethernet/chelsio/cxgb4/cxgb4_debugfs.c

index 0a87a3247464fdd1939d8bcb5867a9f0e735cf02..b4ace194049799f94667816a04237e2a84da793b 100644 (file)
@@ -1128,18 +1128,26 @@ static const struct file_operations devlog_fops = {
 static int mbox_show(struct seq_file *seq, void *v)
 {
        static const char * const owner[] = { "none", "FW", "driver",
-                                             "unknown" };
+                                             "unknown", "<unread>" };
 
        int i;
        unsigned int mbox = (uintptr_t)seq->private & 7;
        struct adapter *adap = seq->private - mbox;
        void __iomem *addr = adap->regs + PF_REG(mbox, CIM_PF_MAILBOX_DATA_A);
-       unsigned int ctrl_reg = (is_t4(adap->params.chip)
-                                ? CIM_PF_MAILBOX_CTRL_A
-                                : CIM_PF_MAILBOX_CTRL_SHADOW_COPY_A);
-       void __iomem *ctrl = adap->regs + PF_REG(mbox, ctrl_reg);
 
-       i = MBOWNER_G(readl(ctrl));
+       /* 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));
+       }
+
        seq_printf(seq, "mailbox owned by %s\n\n", owner[i]);
 
        for (i = 0; i < MBOX_LEN; i += 8)