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>

diff --git a/drivers/tty/serial/8250.c b/drivers/tty/serial/8250.c
index eeadf1b8e093202234b30c688490da2de10a3c04..3a8e5bfe17e28da7e46f4edfb909b7389f44ceb9 100644 (file)
--- a/drivers/tty/serial/8250.c
+++ b/drivers/tty/serial/8250.c
@@ -1619,11 +1619,13 @@ static irqreturn_t serial8250_interrupt(int irq, void *dev_id)
        do {
                struct uart_8250_port *up;
                struct uart_port *port;
+               bool skip;
 
                up = list_entry(l, struct uart_8250_port, list);
                port = &up->port;
+               skip = pass_counter && up->port.flags & UPF_IIR_ONCE;
 
-               if (port->handle_irq(port)) {
+               if (!skip && port->handle_irq(port)) {
                        handled = 1;
                        end = NULL;
                } else if (end == NULL)

diff --git a/drivers/tty/serial/8250_pci.c b/drivers/tty/serial/8250_pci.c
index 825937a5f21098857eb802a4303d46b9aac29909..8742ef5be6ba4cc7897b5c621bb47069b8541d49 100644 (file)
--- 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
         */

diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 945e02cae614188920d8f02f57f4fe4c4a1ffa35..b67305e3ad57a5078b79fec8bca9f060739e08e1 100644 (file)
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -351,6 +351,7 @@ struct uart_port {
 #define UPF_CONS_FLOW          ((__force upf_t) (1 << 23))
 #define UPF_SHARE_IRQ          ((__force upf_t) (1 << 24))
 #define UPF_EXAR_EFR           ((__force upf_t) (1 << 25))
+#define UPF_IIR_ONCE           ((__force upf_t) (1 << 26))
 /* The exact UART type is known and should not be probed.  */
 #define UPF_FIXED_TYPE         ((__force upf_t) (1 << 27))
 #define UPF_BOOT_AUTOCONF      ((__force upf_t) (1 << 28))