serial/8250_pci: setup-quirk workaround for the kt serial controller

Workaround dropped notifications in the iir register.  Prevent reads
coincident with new interrupt notifications by reading the iir at most
once per interrupt.

Reported-by: Nhan H Mai <nhan.h.mai@intel.com>
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, 16 insertions, 1 deletions

diff --git a/drivers/tty/serial/8250_pci.c b/drivers/tty/serial/8250_pci.c
index 825937a5f210..8742ef5be6ba 100644
--- a/drivers/tty/serial/8250_pci.c
+++ b/drivers/tty/serial/8250_pci.c
@@ -1092,6 +1092,14 @@ static int skip_tx_en_setup(struct serial_private *priv,
         return pci_default_setup(priv, board, port, idx);
 }
 
+static int kt_serial_setup(struct serial_private *priv,
+                           const struct pciserial_board *board,
+                           struct uart_port *port, int idx)
+{
+        port->flags |= UPF_IIR_ONCE;
+        return skip_tx_en_setup(priv, board, port, idx);
+}
+
 static int pci_eg20t_init(struct pci_dev *dev)
 {
 #if defined(CONFIG_SERIAL_PCH_UART) || defined(CONFIG_SERIAL_PCH_UART_MODULE)
@@ -1110,7 +1118,6 @@ pci_xr17c154_setup(struct serial_private *priv,
         return pci_default_setup(priv, board, port, idx);
 }
 
-/* This should be in linux/pci_ids.h */
 #define PCI_VENDOR_ID_SBSMODULARIO      0x124B
 #define PCI_SUBVENDOR_ID_SBSMODULARIO   0x124B
 #define PCI_DEVICE_ID_OCTPRO            0x0001
@@ -1136,6 +1143,7 @@ pci_xr17c154_setup(struct serial_private *priv,
 #define PCI_DEVICE_ID_OXSEMI_16PCI958   0x9538
 #define PCIE_DEVICE_ID_NEO_2_OX_IBM     0x00F6
 #define PCI_DEVICE_ID_PLX_CRONYX_OMEGA  0xc001
+#define PCI_DEVICE_ID_INTEL_PATSBURG_KT 0x1d3d
 
 /* Unknown vendors/cards - this should not be in linux/pci_ids.h */
 #define PCI_SUBDEVICE_ID_UNKNOWN_0x1584 0x1584
@@ -1220,6 +1228,13 @@ static struct pci_serial_quirk pci_serial_quirks[] __refdata = {
                 .subdevice      = PCI_ANY_ID,
                 .setup          = ce4100_serial_setup,
         },
+        {
+                .vendor         = PCI_VENDOR_ID_INTEL,
+                .device         = PCI_DEVICE_ID_INTEL_PATSBURG_KT,
+                .subvendor      = PCI_ANY_ID,
+                .subdevice      = PCI_ANY_ID,
+                .setup          = kt_serial_setup,
+        },
         /*
          * ITE
          */