serial: 8250_exar: Fix number of ports for Commtech PCIe cards

The following in 8250_exar.c line 589 is used to determine the number
of ports for each Exar board:

nr_ports = board->num_ports ? board->num_ports : pcidev->device & 0x0f;

If the number of ports a card has is not explicitly specified, it defaults
to the rightmost 4 bits of the PCI device ID. This is prone to error since
not all PCI device IDs contain a number which corresponds to the number of
ports that card provides.

This particular case involves COMMTECH_4222PCIE, COMMTECH_4224PCIE and
COMMTECH_4228PCIE cards with device IDs 0x0022, 0x0020 and 0x0021.
Currently the multiport cards receive 2, 0 and 1 port instead of 2, 4 and
8 ports respectively.

To fix this, each Commtech Fastcom PCIe card is given a struct where the
number of ports is explicitly specified. This ensures 'board->num_ports'
is used instead of the default 'pcidev->device & 0x0f'.

Fixes: d0aeaa83 ("serial: exar: split out the exar code from 8250_pci")
Signed-off-by: Valmer Huhn <valmer.huhn@concurrent-rt.com>
Tested-by: Valmer Huhn <valmer.huhn@concurrent-rt.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200813165255.GC345440@icarus.concurrent-rt.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

@@ -744,6 +744,24 @@ static const struct exar8250_board pbn_exar_XR17V35x = {
 	.exit		= pci_xr17v35x_exit,
 };
 
+static const struct exar8250_board pbn_fastcom35x_2 = {
+	.num_ports	= 2,
+	.setup		= pci_xr17v35x_setup,
+	.exit		= pci_xr17v35x_exit,
+};
+
+static const struct exar8250_board pbn_fastcom35x_4 = {
+	.num_ports	= 4,
+	.setup		= pci_xr17v35x_setup,
+	.exit		= pci_xr17v35x_exit,
+};
+
+static const struct exar8250_board pbn_fastcom35x_8 = {
+	.num_ports	= 8,
+	.setup		= pci_xr17v35x_setup,
+	.exit		= pci_xr17v35x_exit,
+};
+
 static const struct exar8250_board pbn_exar_XR17V4358 = {
 	.num_ports	= 12,
 	.setup		= pci_xr17v35x_setup,
@@ -811,9 +829,9 @@ static const struct pci_device_id exar_pci_tbl[] = {
 	EXAR_DEVICE(EXAR, XR17V358, pbn_exar_XR17V35x),
 	EXAR_DEVICE(EXAR, XR17V4358, pbn_exar_XR17V4358),
 	EXAR_DEVICE(EXAR, XR17V8358, pbn_exar_XR17V8358),
-	EXAR_DEVICE(COMMTECH, 4222PCIE, pbn_exar_XR17V35x),
-	EXAR_DEVICE(COMMTECH, 4224PCIE, pbn_exar_XR17V35x),
-	EXAR_DEVICE(COMMTECH, 4228PCIE, pbn_exar_XR17V35x),
+	EXAR_DEVICE(COMMTECH, 4222PCIE, pbn_fastcom35x_2),
+	EXAR_DEVICE(COMMTECH, 4224PCIE, pbn_fastcom35x_4),
+	EXAR_DEVICE(COMMTECH, 4228PCIE, pbn_fastcom35x_8),
 
 	EXAR_DEVICE(COMMTECH, 4222PCI335, pbn_fastcom335_2),
 	EXAR_DEVICE(COMMTECH, 4224PCI335, pbn_fastcom335_4),