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From: Philippe Langlais on 5 Aug 2010 08:40
UART Features extract from STEricsson U6715 data-sheet (arm926 SoC for mobile phone):
* Fully compatible with industry standard 16C550 and 16C450 from various
manufacturers
* RX and TX 64 byte FIFO reduces CPU interrupts
* Full double buffering
* Modem control signals include CTS, RTS, (and DSR, DTR on UART1 only)
* Automatic baud rate selection
* Manual or automatic RTS/CTS smart hardware flow control
* Programmable serial characteristics:
– Baud rate generation (50 to 3.25M baud)
– 5, 6, 7 or 8-bit characters
– Even, odd or no-parity bit generation and detection
– 1, 1.5 or 2 stop bit generation
* Independent control of transmit, receive, line status, data set interrupts and FIFOs
* Full status-reporting capabilities
* Separate DMA signaling for RX and TX
* Timed interrupt to spread receive interrupt on known duration
* DMA time-out interrupt to allow detection of end of reception
* Carkit pulse coding and decoding compliant with USB carkit control interface [40]

In 16550A auto-configuration, if the fifo size is 64 then it's an U6 16550A port.
Add set_termios hook & export serial8250_do_set_termios,
this feature is used in our U6715 8250 platform serial driver, to avoid
hack in 8250.c set_termios.
In this driver the input uart clock frequency depends on baud rate and
is computed in our set_termios override function.

Signed-off-by: Philippe Langlais <philippe.langlais(a)stericsson.com>
---
drivers/serial/8250.c | 39 ++++++++++++++++++++++++++++++++++++---
include/linux/serial.h | 3 ++-
include/linux/serial_8250.h | 5 +++++
include/linux/serial_core.h | 3 +++
4 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 607ed7f..702f0fa 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -300,6 +300,13 @@ static const struct serial8250_config uart_config[] = {
.fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_00,
.flags = UART_CAP_FIFO | UART_CAP_AFE,
},
+ [PORT_U6_16550A] = {
+ .name = "U6_16550A",
+ .fifo_size = 64,
+ .tx_loadsz = 64,
+ .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
+ .flags = UART_CAP_FIFO | UART_CAP_AFE,
+ },
};

#if defined (CONFIG_SERIAL_8250_AU1X00)
@@ -1075,6 +1082,15 @@ static void autoconfig_16550a(struct uart_8250_port *up)
DEBUG_AUTOCONF("Couldn't force IER_UUE to 0 ");
}
serial_outp(up, UART_IER, iersave);
+
+ /*
+ * We distinguish between 16550A and U6 16550A by counting
+ * how many bytes are in the FIFO.
+ */
+ if (up->port.type == PORT_16550A && size_fifo(up) == 64) {
+ up->port.type = PORT_U6_16550A;
+ up->capabilities |= UART_CAP_AFE;
+ }
}

/*
@@ -2229,9 +2245,9 @@ static unsigned int serial8250_get_divisor(struct uart_port *port, unsigned int
return quot;
}

-static void
-serial8250_set_termios(struct uart_port *port, struct ktermios *termios,
- struct ktermios *old)
+void
+serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
+ struct ktermios *old)
{
struct uart_8250_port *up = (struct uart_8250_port *)port;
unsigned char cval, fcr = 0;
@@ -2407,6 +2423,17 @@ serial8250_set_termios(struct uart_port *port, struct ktermios *termios,
if (tty_termios_baud_rate(termios))
tty_termios_encode_baud_rate(termios, baud, baud);
}
+EXPORT_SYMBOL(serial8250_do_set_termios);
+
+static void
+serial8250_set_termios(struct uart_port *port, struct ktermios *termios,
+ struct ktermios *old)
+{
+ if (port->set_termios)
+ port->set_termios(port, termios, old);
+ else
+ serial8250_do_set_termios(port, termios, old);
+}

static void
serial8250_set_ldisc(struct uart_port *port, int new)
@@ -2917,6 +2944,8 @@ int __init early_serial_setup(struct uart_port *port)
p->serial_in = port->serial_in;
if (port->serial_out)
p->serial_out = port->serial_out;
+ if (port->set_termios)
+ p->set_termios = port->set_termios;

return 0;
}
@@ -2989,6 +3018,7 @@ static int __devinit serial8250_probe(struct platform_device *dev)
port.type = p->type;
port.serial_in = p->serial_in;
port.serial_out = p->serial_out;
+ port.set_termios = p->set_termios;
port.dev = &dev->dev;
port.irqflags |= irqflag;
ret = serial8250_register_port(&port);
@@ -3152,6 +3182,9 @@ int serial8250_register_port(struct uart_port *port)
uart->port.serial_in = port->serial_in;
if (port->serial_out)
uart->port.serial_out = port->serial_out;
+ /* Possibly override set_termios call */
+ if (port->set_termios)
+ uart->port.set_termios = port->set_termios;

ret = uart_add_one_port(&serial8250_reg, &uart->port);
if (ret == 0)
diff --git a/include/linux/serial.h b/include/linux/serial.h
index c8613c3..06c99b6 100644
--- a/include/linux/serial.h
+++ b/include/linux/serial.h
@@ -77,7 +77,8 @@ struct serial_struct {
#define PORT_16654 11
#define PORT_16850 12
#define PORT_RSA 13 /* RSA-DV II/S card */
-#define PORT_MAX 13
+#define PORT_U6_16550A 14
+#define PORT_MAX 14

#define SERIAL_IO_PORT 0
#define SERIAL_IO_HUB6 1
diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
index fb46aba..7638dea 100644
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -32,6 +32,9 @@ struct plat_serial8250_port {
unsigned int type; /* If UPF_FIXED_TYPE */
unsigned int (*serial_in)(struct uart_port *, int);
void (*serial_out)(struct uart_port *, int, int);
+ void (*set_termios)(struct uart_port *,
+ struct ktermios *new,
+ struct ktermios *old);
};

/*
@@ -71,5 +74,7 @@ extern int early_serial_setup(struct uart_port *port);
extern int serial8250_find_port(struct uart_port *p);
extern int serial8250_find_port_for_earlycon(void);
extern int setup_early_serial8250_console(char *cmdline);
+extern void serial8250_do_set_termios(struct uart_port *port,
+ struct ktermios *termios, struct ktermios *old);

#endif
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 18f2fe0..119354f 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -279,6 +279,9 @@ struct uart_port {
unsigned char __iomem *membase; /* read/write[bwl] */
unsigned int (*serial_in)(struct uart_port *, int);
void (*serial_out)(struct uart_port *, int, int);
+ void (*set_termios)(struct uart_port *,
+ struct ktermios *new,
+ struct ktermios *old);
unsigned int irq; /* irq number */
unsigned long irqflags; /* irq flags */
unsigned int uartclk; /* base uart clock */
--
1.7.1

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Prev: [PATCH] timekeeping: Fix overflow in rawtime tv_nsec on 32 bit archs
Next: direct-io regression [Was: How to track down abysmal performance ata - raid1 - crypto - vg/lv - xfs]