xen: Restore the BAR and PCI command after resume.

Certain PCI serial cards just don't want to remember
what they are when they come out of resume. Save
the BAR and the PCI command values before we suspend and
write them back in when we resume.

Signed-off-by: Roger Cruz <roger.cruz@virtualcomputer.com>
Signed-off-by: Tom Goetz <tom.goetz@virtualcomputer.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

xen/drivers/char/ns16550.c

@@ -49,6 +49,7 @@ static struct ns16550 {
     unsigned int ps_bdf[3]; /* pci serial port BDF */
     bool_t pb_bdf_enable;   /* if =1, pb-bdf effective, port behind bridge */
     bool_t ps_bdf_enable;   /* if =1, ps_bdf effective, port on pci card */
+    int bar0, cr;
 } ns16550_com[2] = { { 0 } };
 
 /* Register offsets */
@@ -333,13 +334,30 @@ static void __init ns16550_init_postirq(struct serial_port *port)
 static void ns16550_suspend(struct serial_port *port)
 {
     struct ns16550 *uart = port->uart;
+
     stop_timer(&uart->timer);
+
+    if (uart->bar0) {
+       uart->bar0 = pci_conf_read32(uart->pb_bdf[0], uart->pb_bdf[1], uart->pb_bdf[2],
+                                    PCI_BASE_ADDRESS_0);
+       uart->cr = pci_conf_read32(uart->pb_bdf[0], uart->pb_bdf[1], uart->pb_bdf[2],
+                                    PCI_COMMAND);
+    }
 }
 
 static void ns16550_resume(struct serial_port *port)
 {
+    struct ns16550 *uart = port->uart;
+
     ns16550_setup_preirq(port->uart);
     ns16550_setup_postirq(port->uart);
+
+    if (uart->bar0) {
+       pci_conf_write32(uart->pb_bdf[0], uart->pb_bdf[1], uart->pb_bdf[2],
+                        PCI_BASE_ADDRESS_0, uart->bar0);
+       pci_conf_write32(uart->pb_bdf[0], uart->pb_bdf[1], uart->pb_bdf[2],
+                        PCI_COMMAND, uart->cr);
+    }
 }
 
 #ifdef CONFIG_X86
@@ -479,6 +497,10 @@ magic_uart_config (struct ns16550 *uart,int skip_amt)
               if ((len & 0xffff) != 0xfff9)
                 continue;
 
+              uart->pb_bdf[0] = b;
+              uart->pb_bdf[1] = d;
+              uart->pb_bdf[2] = f;
+              uart->bar0 = bar0;
               uart->io_base = bar0 & 0xfffe;
               uart->irq = 0;