[PATCH v3 0/2] drivers: serial: Aspeed VUART driver

[PATCH v3 0/2] drivers: serial: Aspeed VUART driver

[Joel Stanley]

This is v3 of a driver for the Aspeed VUART. This version addresses feedback
from Andy and Greg, and includes Rob's ack for the bindings change.

The VUART is a serial device on the BMC side of the LPC bus that connects a BMC
to it's host processor.

We add a flag to the serial core to allow the driver to skip probing of the
THRE irq behaviour, which could hang due to the host not reading bytes out of
the buffer.

We've been using this on systems for over a year, so it has seen a good amount
of testing.

Cheers,

Joel

Jeremy Kerr (1):
  drivers/serial: Add driver for Aspeed virtual UART

Joel Stanley (1):
  serial: 8250: Add flag so drivers can avoid THRE probe

 Documentation/ABI/stable/sysfs-driver-aspeed-vuart |  15 +
 Documentation/devicetree/bindings/serial/8250.txt  |   2 +
 drivers/tty/serial/8250/8250_aspeed_vuart.c        | 323 +++++++++++++++++++++
 drivers/tty/serial/8250/8250_port.c                |   2 +-
 drivers/tty/serial/8250/Kconfig                    |  10 +
 drivers/tty/serial/8250/Makefile                   |   1 +
 include/linux/serial_core.h                        |   1 +
 7 files changed, 353 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/ABI/stable/sysfs-driver-aspeed-vuart
 create mode 100644 drivers/tty/serial/8250/8250_aspeed_vuart.c

-- 
2.11.0

[PATCH v3 1/2] serial: 8250: Add flag so drivers can avoid THRE probe

[Joel Stanley]

The probing of THRE irq behaviour assumes the other end will be reading
bytes out of the buffer in order to probe the port at driver init. In
some cases the other end cannot be relied upon to read these bytes, so
provide a flag for them to skip this step.

Bit 19 was chosen as the flags are a int and the top bits are taken.

Acked-by: Benjamin Herrenschmidt <benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
Signed-off-by: Joel Stanley <joel-U3u1mxZcP9KHXe+LvDLADg@public.gmane.org>

---
v3:
 - Correct the bit number in the changelog

v2:
 - No change

 drivers/tty/serial/8250/8250_port.c | 2 +-
 include/linux/serial_core.h         | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 6119516ef5fc..60a6c247340f 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2229,7 +2229,7 @@ int serial8250_do_startup(struct uart_port *port)
 		}
 	}
 
-	if (port->irq) {
+	if (port->irq && !(up->port.flags & UPF_NO_THRE_TEST)) {
 		unsigned char iir1;
 		/*
 		 * Test for UARTs that do not reassert THRE when the
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 58484fb35cc8..260245deec94 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -195,6 +195,7 @@ struct uart_port {
 #define UPF_NO_TXEN_TEST	((__force upf_t) (1 << 15))
 #define UPF_MAGIC_MULTIPLIER	((__force upf_t) ASYNC_MAGIC_MULTIPLIER /* 16 */ )
 
+#define UPF_NO_THRE_TEST	((__force upf_t) (1 << 19))
 /* Port has hardware-assisted h/w flow control */
 #define UPF_AUTO_CTS		((__force upf_t) (1 << 20))
 #define UPF_AUTO_RTS		((__force upf_t) (1 << 21))
-- 
2.11.0

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[PATCH v3 0/2] drivers: serial: Aspeed VUART driver

[Joel Stanley]

This is v3 of a driver for the Aspeed VUART. This version addresses feedback
from Andy and Greg, and includes Rob's ack for the bindings change.

The VUART is a serial device on the BMC side of the LPC bus that connects a BMC
to it's host processor.

We add a flag to the serial core to allow the driver to skip probing of the
THRE irq behaviour, which could hang due to the host not reading bytes out of
the buffer.

We've been using this on systems for over a year, so it has seen a good amount
of testing.

Cheers,

Joel

Jeremy Kerr (1):
  drivers/serial: Add driver for Aspeed virtual UART

Joel Stanley (1):
  serial: 8250: Add flag so drivers can avoid THRE probe

 Documentation/ABI/stable/sysfs-driver-aspeed-vuart |  15 +
 Documentation/devicetree/bindings/serial/8250.txt  |   2 +
 drivers/tty/serial/8250/8250_aspeed_vuart.c        | 323 +++++++++++++++++++++
 drivers/tty/serial/8250/8250_port.c                |   2 +-
 drivers/tty/serial/8250/Kconfig                    |  10 +
 drivers/tty/serial/8250/Makefile                   |   1 +
 include/linux/serial_core.h                        |   1 +
 7 files changed, 353 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/ABI/stable/sysfs-driver-aspeed-vuart
 create mode 100644 drivers/tty/serial/8250/8250_aspeed_vuart.c

-- 
2.11.0

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[PATCH v3 1/2] serial: 8250: Add flag so drivers can avoid THRE probe

[Joel Stanley]

The probing of THRE irq behaviour assumes the other end will be reading
bytes out of the buffer in order to probe the port at driver init. In
some cases the other end cannot be relied upon to read these bytes, so
provide a flag for them to skip this step.

Bit 19 was chosen as the flags are a int and the top bits are taken.

Acked-by: Benjamin Herrenschmidt <benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
Signed-off-by: Joel Stanley <joel-U3u1mxZcP9KHXe+LvDLADg@public.gmane.org>

---
v3:
 - Correct the bit number in the changelog

v2:
 - No change

 drivers/tty/serial/8250/8250_port.c | 2 +-
 include/linux/serial_core.h         | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 6119516ef5fc..60a6c247340f 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2229,7 +2229,7 @@ int serial8250_do_startup(struct uart_port *port)
 		}
 	}
 
-	if (port->irq) {
+	if (port->irq && !(up->port.flags & UPF_NO_THRE_TEST)) {
 		unsigned char iir1;
 		/*
 		 * Test for UARTs that do not reassert THRE when the
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 58484fb35cc8..260245deec94 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -195,6 +195,7 @@ struct uart_port {
 #define UPF_NO_TXEN_TEST	((__force upf_t) (1 << 15))
 #define UPF_MAGIC_MULTIPLIER	((__force upf_t) ASYNC_MAGIC_MULTIPLIER /* 16 */ )
 
+#define UPF_NO_THRE_TEST	((__force upf_t) (1 << 19))
 /* Port has hardware-assisted h/w flow control */
 #define UPF_AUTO_CTS		((__force upf_t) (1 << 20))
 #define UPF_AUTO_RTS		((__force upf_t) (1 << 21))
-- 
2.11.0

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