serial: 8250_pci: Implement MSI(-X) support

There may be setups, where legacy interrupts are not available. This is
the caese, e.g., when Linux runs as guest (aka. non-root cell) of the
partitioning hypervisor Jailhouse. There, only MSI(-X) interrupts are
available for guests.

But the 8250_pci driver currently only supports legacy ints. So let's
enable MSI(-X) interrupts.

Nevertheless, this needs to handled with care: while many 8250 devices
actually claim to support MSI(-X) interrupts it should not be enabled be
default. I had at least one device in my hands with broken MSI
implementation.

So better introduce a whitelist with devices that are known to support
MSI(-X) interrupts. I tested all devices mentioned in the patch.

Signed-off-by: Ralf Ramsauer <ralf.ramsauer@oth-regensburg.de>
Link: https://lore.kernel.org/r/20190812112152.693622-1-ralf.ramsauer@oth-regensburg.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
index 83e21b6..6adbadd 100644 (file)
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -58,6 +58,16 @@ struct serial_private {
        int                     line[0];
 };
 
+static const struct pci_device_id pci_use_msi[] = {
+       { PCI_DEVICE_SUB(PCI_VENDOR_ID_NETMOS, PCI_DEVICE_ID_NETMOS_9900,
+                        0xA000, 0x1000) },
+       { PCI_DEVICE_SUB(PCI_VENDOR_ID_NETMOS, PCI_DEVICE_ID_NETMOS_9912,
+                        0xA000, 0x1000) },
+       { PCI_DEVICE_SUB(PCI_VENDOR_ID_NETMOS, PCI_DEVICE_ID_NETMOS_9922,
+                        0xA000, 0x1000) },
+       { }
+};
+
 static int pci_default_setup(struct serial_private*,
          const struct pciserial_board*, struct uart_8250_port *, int);
 
@@ -4155,7 +4165,22 @@ pciserial_init_ports(struct pci_dev *dev, const struct pciserial_board *board)
        memset(&uart, 0, sizeof(uart));
        uart.port.flags = UPF_SKIP_TEST | UPF_BOOT_AUTOCONF | UPF_SHARE_IRQ;
        uart.port.uartclk = board->base_baud * 16;
-       uart.port.irq = get_pci_irq(dev, board);
+
+       if (pci_match_id(pci_use_msi, dev)) {
+               dev_dbg(&dev->dev, "Using MSI(-X) interrupts\n");
+               pci_set_master(dev);
+               rc = pci_alloc_irq_vectors(dev, 1, 1, PCI_IRQ_ALL_TYPES);
+       } else {
+               dev_dbg(&dev->dev, "Using legacy interrupts\n");
+               rc = pci_alloc_irq_vectors(dev, 1, 1, PCI_IRQ_LEGACY);
+       }
+       if (rc < 0) {
+               kfree(priv);
+               priv = ERR_PTR(rc);
+               goto err_deinit;
+       }
+
+       uart.port.irq = pci_irq_vector(dev, 0);
        uart.port.dev = &dev->dev;
 
        for (i = 0; i < nr_ports; i++) {