[PATCH] ns1650: refactor interrupt handling in ns16550_uart_dt_init()

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

In ns16550_init_postirq() there is the following check:
    if ( uart->irq > 0 )
    {
        uart->irqaction.handler = ns16550_interrupt;
        uart->irqaction.name    = "ns16550";
        uart->irqaction.dev_id  = port;
        if ( (rc = setup_irq(uart->irq, 0, &uart->irqaction)) != 0 )
            printk("ERROR: Failed to allocate ns16550 IRQ %d\n", uart->irq);
    }

Thereby to have ns16550 work in polling mode uart->irq, should be equal to 0.

So it is needed to relax the following check in ns16550_uart_dt_init():
    res = platform_get_irq(dev, 0);
    if ( ! res )
        return -EINVAL;
    uart->irq = res;
If 'res' equals to -1 then polling mode should be used instead of return
-EINVAL.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
 xen/drivers/char/ns16550.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
index 2aed6ec707..f30f10d175 100644
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -1791,8 +1791,16 @@ static int __init ns16550_uart_dt_init(struct 
dt_device_node *dev,
     }
 
     res = platform_get_irq(dev, 0);
-    if ( ! res )
-        return -EINVAL;
+    if ( res == -1 )
+    {
+        printk("ns1650: polling will be used\n");
+        /*
+         * There is the check 'if ( uart->irq > 0 )' in ns16550_init_postirq().
+         * If the check is true then interrupt mode will be used otherwise
+         * ( when irq = 0 )polling.
+         */
+        res = 0;
+    }
     uart->irq = res;
 
     uart->dw_usr_bsy = dt_device_is_compatible(dev, "snps,dw-apb-uart");
-- 
2.41.0