Subject: [PATCH 1/2] serial: Add flush_buffer() operation to uart_ops (6bb0e3a5) · Commits · 戴 / test

Serial drivers using DMA (like the atmel_serial 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. Signed-off-by:

Haavard Skinnemoen <haavard.skinnemoen@atmel.com> Acked-by:

Alan Cox <alan@redhat.com> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

Documentation/serial/driver

+11 −0

Original line number	Diff line number	Diff line
		@@ -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

drivers/serial/serial_core.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -573,6 +573,8 @@ static void uart_flush_buffer(struct tty_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);
		}

include/linux/serial_core.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -190,6 +190,7 @@ 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 ktermios *new,
		struct ktermios *old);
		void (set_ldisc)(struct uart_port );

Original line number	Diff line number	Diff line
		@@ -190,6 +190,7 @@ 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 ktermios *new,
		struct ktermios *old);
		void (set_ldisc)(struct uart_port );

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