PCI: designware: Check for iATU unroll only on platforms that use ATU

Previously we checked for iATU unroll support by reading PCIE_ATU_VIEWPORT
even on platforms, e.g., Keystone, that do not have ATU ports.  This can
cause bad behavior such as asynchronous external aborts:

  OF: PCI:   MEM 0x60000000..0x6fffffff -> 0x60000000
  Unhandled fault: asynchronous external abort (0x1211) at 0x00000000
  pgd = c0003000
  [00000000] *pgd=80000800004003, *pmd=00000000
  Internal error: : 1211 [#1] PREEMPT SMP ARM
  Modules linked in:
  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.9.0-00009-g6ff59d2-dirty #7
  Hardware name: Keystone
  task: eb878000 task.stack: eb866000
  PC is at dw_pcie_setup_rc+0x24/0x380
  LR is at ks_pcie_host_init+0x10/0x170

Move the dw_pcie_iatu_unroll_enabled() check so we only call it on
platforms that do not use the ATU.  These platforms supply their own
->rd_other_conf() and ->wr_other_conf() methods.

[bhelgaas: changelog]
Fixes: a0601a470537 ("PCI: designware: Add iATU Unroll feature")
Fixes: 416379f9ebde ("PCI: designware: Check for iATU unroll support after initializing host")
Tested-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-By: Joao Pinto <jpinto@synopsys.com>
CC: stable@vger.kernel.org	# v4.9+

drivers/pci/host/pcie-designware.c

@@ -807,11 +807,6 @@ void dw_pcie_setup_rc(struct pcie_port *pp)
 {
 	u32 val;
 
-	/* get iATU unroll support */
-	pp->iatu_unroll_enabled = dw_pcie_iatu_unroll_enabled(pp);
-	dev_dbg(pp->dev, "iATU unroll: %s\n",
-		pp->iatu_unroll_enabled ? "enabled" : "disabled");
-
 	/* set the number of lanes */
 	val = dw_pcie_readl_rc(pp, PCIE_PORT_LINK_CONTROL);
 	val &= ~PORT_LINK_MODE_MASK;
@@ -882,6 +877,11 @@ void dw_pcie_setup_rc(struct pcie_port *pp)
 	 * we should not program the ATU here.
 	 */
 	if (!pp->ops->rd_other_conf) {
+		/* get iATU unroll support */
+		pp->iatu_unroll_enabled = dw_pcie_iatu_unroll_enabled(pp);
+		dev_dbg(pp->dev, "iATU unroll: %s\n",
+			pp->iatu_unroll_enabled ? "enabled" : "disabled");
+
 		dw_pcie_prog_outbound_atu(pp, PCIE_ATU_REGION_INDEX0,
 					  PCIE_ATU_TYPE_MEM, pp->mem_base,
 					  pp->mem_bus_addr, pp->mem_size);