tg3: tg3_disable_ints using uninitialized mailbox value to disable interrupts

During driver load in tg3_init_one, if the driver detects DMA activity before
intializing the chip tg3_halt is called. As part of tg3_halt interrupts are
disabled using routine tg3_disable_ints. This routine was using mailbox value
which was not initialized (default value is 0). As a result driver was writing
0x00000001 to pci config space register 0, which is the vendor id / device id.

This driver bug was exposed because of the commit a7877b17a667 (PCI: Check only
the Vendor ID to identify Configuration Request Retry). Also this issue is only
seen in older generation chipsets like 5722 because config space write to offset
0 from driver is possible. The newer generation chips ignore writes to offset 0.
Also without commit a7877b17a667, for these older chips when a GRC reset is
issued the Bootcode would reprogram the vendor id/device id, which is the reason
this bug was masked earlier.

Fixed by initializing the interrupt mailbox registers before calling tg3_halt.

Please queue for -stable.
Reported-by: Nils Holland <nholland@tisys.org>
Reported-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Prashant Sreedharan <prashant@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/tg3.c

@@ -17800,23 +17800,6 @@ static int tg3_init_one(struct pci_dev *pdev,
 		goto err_out_apeunmap;
 	}
 
-	/*
-	 * Reset chip in case UNDI or EFI driver did not shutdown
-	 * DMA self test will enable WDMAC and we'll see (spurious)
-	 * pending DMA on the PCI bus at that point.
-	 */
-	if ((tr32(HOSTCC_MODE) & HOSTCC_MODE_ENABLE) ||
-	    (tr32(WDMAC_MODE) & WDMAC_MODE_ENABLE)) {
-		tw32(MEMARB_MODE, MEMARB_MODE_ENABLE);
-		tg3_halt(tp, RESET_KIND_SHUTDOWN, 1);
-	}
-
-	err = tg3_test_dma(tp);
-	if (err) {
-		dev_err(&pdev->dev, "DMA engine test failed, aborting\n");
-		goto err_out_apeunmap;
-	}
-
 	intmbx = MAILBOX_INTERRUPT_0 + TG3_64BIT_REG_LOW;
 	rcvmbx = MAILBOX_RCVRET_CON_IDX_0 + TG3_64BIT_REG_LOW;
 	sndmbx = MAILBOX_SNDHOST_PROD_IDX_0 + TG3_64BIT_REG_LOW;
@@ -17861,6 +17844,23 @@ static int tg3_init_one(struct pci_dev *pdev,
 			sndmbx += 0xc;
 	}
 
+	/*
+	 * Reset chip in case UNDI or EFI driver did not shutdown
+	 * DMA self test will enable WDMAC and we'll see (spurious)
+	 * pending DMA on the PCI bus at that point.
+	 */
+	if ((tr32(HOSTCC_MODE) & HOSTCC_MODE_ENABLE) ||
+	    (tr32(WDMAC_MODE) & WDMAC_MODE_ENABLE)) {
+		tw32(MEMARB_MODE, MEMARB_MODE_ENABLE);
+		tg3_halt(tp, RESET_KIND_SHUTDOWN, 1);
+	}
+
+	err = tg3_test_dma(tp);
+	if (err) {
+		dev_err(&pdev->dev, "DMA engine test failed, aborting\n");
+		goto err_out_apeunmap;
+	}
+
 	tg3_init_coal(tp);
 
 	pci_set_drvdata(pdev, dev);