serial: 8250_exar: Absorb remaining 8250_port INT0 support

Move INT0 clearing out of common, per-port serial8250_do_startup()
into PCI device probe/resume.

As described in commit 2c0ac5b4 ("serial: exar: Fix stuck MSIs"),
the purpose of clearing INT0 is to prevent the PCI interrupt line from
becoming stuck asserted, "which is fatal with edge-triggered MSIs".

Like the clearing via interrupt handler that moved from common code in
commit c7e1b405 ("tty: serial: exar: Relocate sleep wake-up
handling"), this clearing at startup can be better handled at the PCI
device level.

Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Signed-off-by: Aaron Sierra <asierra@xes-inc.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20190801185956.3222-1-asierra@xes-inc.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_exar.c

@@ -493,6 +493,16 @@ static void pci_xr17v35x_exit(struct pci_dev *pcidev)
 	port->port.private_data = NULL;
 }
 
+static inline void exar_misc_clear(struct exar8250 *priv)
+{
+	/* Clear all PCI interrupts by reading INT0. No effect on IIR */
+	readb(priv->virt + UART_EXAR_INT0);
+
+	/* Clear INT0 for Expansion Interface slave ports, too */
+	if (priv->board->num_ports > 8)
+		readb(priv->virt + 0x2000 + UART_EXAR_INT0);
+}
+
 /*
  * These Exar UARTs have an extra interrupt indicator that could fire for a
  * few interrupts that are not presented/cleared through IIR.  One of which is
@@ -504,14 +514,7 @@ static void pci_xr17v35x_exit(struct pci_dev *pcidev)
  */
 static irqreturn_t exar_misc_handler(int irq, void *data)
 {
-	struct exar8250 *priv = data;
-
-	/* Clear all PCI interrupts by reading INT0. No effect on IIR */
-	readb(priv->virt + UART_EXAR_INT0);
-
-	/* Clear INT0 for Expansion Interface slave ports, too */
-	if (priv->board->num_ports > 8)
-		readb(priv->virt + 0x2000 + UART_EXAR_INT0);
+	exar_misc_clear(data);
 
 	return IRQ_HANDLED;
 }
@@ -584,6 +587,9 @@ exar_pci_probe(struct pci_dev *pcidev, const struct pci_device_id *ent)
 	if (rc)
 		return rc;
 
+	/* Clear interrupts */
+	exar_misc_clear(priv);
+
 	for (i = 0; i < nr_ports && i < maxnr; i++) {
 		rc = board->setup(priv, pcidev, &uart, i);
 		if (rc) {
@@ -642,6 +648,8 @@ static int __maybe_unused exar_resume(struct device *dev)
 	struct exar8250 *priv = dev_get_drvdata(dev);
 	unsigned int i;
 
+	exar_misc_clear(priv);
+
 	for (i = 0; i < priv->nr; i++)
 		if (priv->line[i] >= 0)
 			serial8250_resume_port(priv->line[i]);

drivers/tty/serial/8250/8250_port.c

@@ -40,11 +40,6 @@
 
 #include "8250.h"
 
-/*
- * These are definitions for the Exar XR17V35X and XR17(C|D)15X
- */
-#define UART_EXAR_INT0		0x80
-
 /* Nuvoton NPCM timeout register */
 #define UART_NPCM_TOR          7
 #define UART_NPCM_TOIE         BIT(7)  /* Timeout Interrupt Enable */
@@ -2138,8 +2133,6 @@ int serial8250_do_startup(struct uart_port *port)
 	serial_port_in(port, UART_RX);
 	serial_port_in(port, UART_IIR);
 	serial_port_in(port, UART_MSR);
-	if ((port->type == PORT_XR17V35X) || (port->type == PORT_XR17D15X))
-		serial_port_in(port, UART_EXAR_INT0);
 
 	/*
 	 * At this point, there's no way the LSR could still be 0xff;
@@ -2297,8 +2290,6 @@ int serial8250_do_startup(struct uart_port *port)
 	serial_port_in(port, UART_RX);
 	serial_port_in(port, UART_IIR);
 	serial_port_in(port, UART_MSR);
-	if ((port->type == PORT_XR17V35X) || (port->type == PORT_XR17D15X))
-		serial_port_in(port, UART_EXAR_INT0);
 	up->lsr_saved_flags = 0;
 	up->msr_saved_flags = 0;