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Subject[PATCH] serial/8250_pci: add a quirk for the kt serial controller
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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>
---
drivers/tty/serial/8250.c | 6 +++++-
drivers/tty/serial/8250_pci.c | 15 +++++++++++++++
include/linux/pci_ids.h | 1 +
include/linux/serial_core.h | 1 +
4 files changed, 22 insertions(+), 1 deletions(-)
diff --git a/drivers/tty/serial/8250.c b/drivers/tty/serial/8250.c
index 7f50999..513e728 100644
--- a/drivers/tty/serial/8250.c
+++ b/drivers/tty/serial/8250.c
@@ -1652,7 +1652,11 @@ static irqreturn_t serial8250_interrupt(int irq, void *dev_id)

up = list_entry(l, struct uart_8250_port, list);

- iir = serial_in(up, UART_IIR);
+ if (pass_counter && up->port.flags & UPF_IIR_ONCE)
+ iir = UART_IIR_NO_INT;
+ else
+ iir = serial_in(up, UART_IIR);
+
if (!(iir & UART_IIR_NO_INT)) {
serial8250_handle_port(up);

diff --git a/drivers/tty/serial/8250_pci.c b/drivers/tty/serial/8250_pci.c
index 3abeca2..4ad2fb4 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)
@@ -1211,6 +1219,13 @@ 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/pci_ids.h b/include/linux/pci_ids.h
index ae96bbe..ed80d75 100644
--- a/include/linux/pci_ids.h
+++ b/include/linux/pci_ids.h
@@ -2492,6 +2492,7 @@
#define PCI_DEVICE_ID_INTEL_IOAT 0x1a38
#define PCI_DEVICE_ID_INTEL_COUGARPOINT_LPC_MIN 0x1c41
#define PCI_DEVICE_ID_INTEL_COUGARPOINT_LPC_MAX 0x1c5f
+#define PCI_DEVICE_ID_INTEL_PATSBURG_KT 0x1d3d
#define PCI_DEVICE_ID_INTEL_PATSBURG_LPC_0 0x1d40
#define PCI_DEVICE_ID_INTEL_PATSBURG_LPC_1 0x1d41
#define PCI_DEVICE_ID_INTEL_PANTHERPOINT_XHCI 0x1e31
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index a5c3114..a66484b3 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -350,6 +350,7 @@ struct uart_port {
#define UPF_MAGIC_MULTIPLIER ((__force upf_t) (1 << 16))
#define UPF_CONS_FLOW ((__force upf_t) (1 << 23))
#define UPF_SHARE_IRQ ((__force upf_t) (1 << 24))
+#define UPF_IIR_ONCE ((__force upf_t) (1 << 25))
/* 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))


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