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From nobody Mon Sep 17 00:00:00 2001
From: Håvard Skinnemoen <hskinnemoen@atmel.com>
Date: Thu Feb 2 15:48:50 2006 +0100
Subject: [PATCH] Add flush_buffer() operation to uart_ops
Serial drivers using DMA (like the Atmel USART3 driver) tend to get
very confused when the xmit buffer is flushed and nobody told them.
They also tend to spew a lot of garbage since the DMA engine keeps
running after the buffer is flushed and possibly refilled with
unrelated data.
This patch adds a new flush_buffer operation to the uart_ops struct,
along with a call to it from uart_flush_buffer() right after the xmit
buffer has been cleared. The driver can implement this in order to
syncronize its internal DMA state with the xmit buffer when the buffer
is flushed.
---
Documentation/serial/driver | 11 +++++++++++
drivers/serial/serial_core.c | 2 ++
include/linux/serial_core.h | 1 +
3 files changed, 14 insertions(+)
Index: linux-2.6.16-avr32/Documentation/serial/driver
===================================================================
--- linux-2.6.16-avr32.orig/Documentation/serial/driver 2006-03-20 06:53:29.000000000 +0100
+++ linux-2.6.16-avr32/Documentation/serial/driver 2006-04-03 18:57:11.000000000 +0200
@@ -186,6 +186,17 @@ hardware.
Locking: port_sem taken.
Interrupts: caller dependent.
+ flush_buffer(port)
+ Flush any write buffers, reset any DMA state and stop any
+ ongoing DMA transfers.
+
+ This will be called whenever the port->info->xmit circular
+ buffer is cleared.
+
+ Locking: port->lock taken.
+ Interrupts: locally disabled.
+ This call must not sleep
+
set_termios(port,termios,oldtermios)
Change the port parameters, including word length, parity, stop
bits. Update read_status_mask and ignore_status_mask to indicate
Index: linux-2.6.16-avr32/drivers/serial/serial_core.c
===================================================================
--- linux-2.6.16-avr32.orig/drivers/serial/serial_core.c 2006-03-20 06:53:29.000000000 +0100
+++ linux-2.6.16-avr32/drivers/serial/serial_core.c 2006-04-03 18:57:11.000000000 +0200
@@ -556,6 +556,8 @@ static void uart_flush_buffer(struct tty
spin_lock_irqsave(&port->lock, flags);
uart_circ_clear(&state->info->xmit);
+ if (port->ops->flush_buffer)
+ port->ops->flush_buffer(port);
spin_unlock_irqrestore(&port->lock, flags);
tty_wakeup(tty);
}
Index: linux-2.6.16-avr32/include/linux/serial_core.h
===================================================================
--- linux-2.6.16-avr32.orig/include/linux/serial_core.h 2006-03-20 06:53:29.000000000 +0100
+++ linux-2.6.16-avr32/include/linux/serial_core.h 2006-04-03 18:57:11.000000000 +0200
@@ -164,6 +164,7 @@ struct uart_ops {
void (*break_ctl)(struct uart_port *, int ctl);
int (*startup)(struct uart_port *);
void (*shutdown)(struct uart_port *);
+ void (*flush_buffer)(struct uart_port *);
void (*set_termios)(struct uart_port *, struct termios *new,
struct termios *old);
void (*pm)(struct uart_port *, unsigned int state,
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