serial/8250_pci: add a "force background timer" flag and use it for the "kt" serial...

Workaround dropped notifications in the iir register.  Register reads
coincident with new interrupt notifications sometimes result in this
device clearing the interrupt event without reporting it in the read
data.

The serial core already has a heuristic for determining when a device
has an untrustworthy iir register.  In this case when we apriori know
that the iir is faulty use a flag (UPF_BUG_THRE) to bypass the test and
force usage of the background timer.

[stable: 3.3.x]
Acked-by: Alan Cox <alan@linux.intel.com>
Cc: stable <stable@vger.kernel.org>
Reported-by: Nhan H Mai <nhan.h.mai@intel.com>
Reported-by: Sudhakar Mamillapalli <sudhakar@fb.com>
Tested-by: Nhan H Mai <nhan.h.mai@intel.com>
Tested-by: Sudhakar Mamillapalli <sudhakar@fb.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250.c b/drivers/tty/serial/8250/8250.c
index 56492d208a7ab14d55ee645eb533516d16a9a8bc..5c27f7e6c9f1b575130eb637c7ab970913851b6a 100644 (file)
--- a/drivers/tty/serial/8250/8250.c
+++ b/drivers/tty/serial/8250/8250.c
@@ -2035,10 +2035,12 @@ static int serial8250_startup(struct uart_port *port)
                spin_unlock_irqrestore(&port->lock, flags);
 
                /*
-                * If the interrupt is not reasserted, setup a timer to
-                * kick the UART on a regular basis.
+                * If the interrupt is not reasserted, or we otherwise
+                * don't trust the iir, setup a timer to kick the UART
+                * on a regular basis.
                 */
-               if (!(iir1 & UART_IIR_NO_INT) && (iir & UART_IIR_NO_INT)) {
+               if ((!(iir1 & UART_IIR_NO_INT) && (iir & UART_IIR_NO_INT)) ||
+                   up->port.flags & UPF_BUG_THRE) {
                        up->bugs |= UART_BUG_THRE;
                        pr_debug("ttyS%d - using backup timer\n",
                                 serial_index(port));

diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
index 105dcfbd3d33282325ad14a97c5a7d23dc67cfe8..858dca865d6ab6b35fd04beb21c826d892050f76 100644 (file)
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_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_BUG_THRE;
+       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
@@ -1140,6 +1147,7 @@ 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
@@ -1224,6 +1232,13 @@ 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 882f1d61aa5603f84eff5d29a9c688491cacb3e4..2db407a400513efcc39ced42b6e94859fb7f417f 100644 (file)
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -357,6 +357,7 @@ 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_BUG_THRE           ((__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))