serial/8250_pci: init-quirk msi support for kt serial controller

The semantics of UPF_IIR_ONCE (once per serial irq) are only guaranteed
if the kt irq is not shared (once per serial isr in the shared case ==
potentially unwanted reads of the IIR).

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/tty/serial/8250_pci.c b/drivers/tty/serial/8250_pci.c
index 8742ef5be6ba..2cbf78f77c4a 100644
--- a/drivers/tty/serial/8250_pci.c
+++ b/drivers/tty/serial/8250_pci.c
@@ -1118,6 +1118,18 @@ pci_xr17c154_setup(struct serial_private *priv,
         return pci_default_setup(priv, board, port, idx);
 }
 
+static int try_enable_msi(struct pci_dev *dev)
+{
+        /* use msi if available, but fallback to legacy otherwise */
+        pci_enable_msi(dev);
+        return 0;
+}
+
+static void disable_msi(struct pci_dev *dev)
+{
+        pci_disable_msi(dev);
+}
+
 #define PCI_VENDOR_ID_SBSMODULARIO      0x124B
 #define PCI_SUBVENDOR_ID_SBSMODULARIO   0x124B
 #define PCI_DEVICE_ID_OCTPRO            0x0001
@@ -1233,7 +1245,9 @@ static struct pci_serial_quirk pci_serial_quirks[] __refdata = {
                 .device         = PCI_DEVICE_ID_INTEL_PATSBURG_KT,
                 .subvendor      = PCI_ANY_ID,
                 .subdevice      = PCI_ANY_ID,
+                .init           = try_enable_msi,
                 .setup          = kt_serial_setup,
+                .exit           = disable_msi,
         },
         /*
          * ITE