Commit bdb70c42 authored by Ilpo Järvinen's avatar Ilpo Järvinen Committed by Greg Kroah-Hartman
Browse files

serial: 8250: Create serial_lsr_in() 



LSR register readers need to be careful in order to not lose bits that
are not preserved across reads. Create a helper that takes care of
storing the non-preserved bits into lsr_save_flags.

Reviewed-by: default avatarAndy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: default avatarIlpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220608095431.18376-3-ilpo.jarvinen@linux.intel.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ce338e44

drivers/tty/serial/8250/8250.h

+20 −0
Original line number Diff line number Diff line
@@ -123,6 +123,26 @@ static inline void serial_out(struct uart_8250_port *up, int offset, int value) 
	up->port.serial_out(&up->port, offset, value);

}



/**

 *	serial_lsr_in - Read LSR register and preserve flags across reads

 *	@up:	uart 8250 port

 *

 *	Read LSR register and handle saving non-preserved flags across reads.

 *	The flags that are not preserved across reads are stored into

 *	up->lsr_saved_flags.

 *

 *	Returns LSR value or'ed with the preserved flags (if any).

 */

static inline unsigned int serial_lsr_in(struct uart_8250_port *up)

{

	unsigned int lsr = up->lsr_saved_flags;



	lsr |= serial_in(up, UART_LSR);

	up->lsr_saved_flags = lsr & LSR_SAVE_FLAGS;



	return lsr;

}



/*

 * For the 16C950

 */

drivers/tty/serial/8250/8250_core.c

+1 −2
Original line number Diff line number Diff line
@@ -276,8 +276,7 @@ static void serial8250_backup_timeout(struct timer_list *t) 
	 * the "Diva" UART used on the management processor on many HP

	 * ia64 and parisc boxes.

	 */

	lsr = serial_in(up, UART_LSR);

	up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;

	lsr = serial_lsr_in(up);

	if ((iir & UART_IIR_NO_INT) && (up->ier & UART_IER_THRI) &&

	    (!uart_circ_empty(&up->port.state->xmit) || up->port.x_char) &&

	    (lsr & UART_LSR_THRE)) {

drivers/tty/serial/8250/8250_port.c

+4 −11
Original line number Diff line number Diff line
@@ -1508,11 +1508,9 @@ static inline void __stop_tx(struct uart_8250_port *p) 
	struct uart_8250_em485 *em485 = p->em485;



	if (em485) {

		unsigned char lsr = serial_in(p, UART_LSR);

		unsigned char lsr = serial_lsr_in(p);

		u64 stop_delay = 0;



		p->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;



		if (!(lsr & UART_LSR_THRE))

			return;

		/*
@@ -1569,10 +1567,8 @@ static inline void __start_tx(struct uart_port *port) 


	if (serial8250_set_THRI(up)) {

		if (up->bugs & UART_BUG_TXEN) {

			unsigned char lsr;

			unsigned char lsr = serial_lsr_in(up);



			lsr = serial_in(up, UART_LSR);

			up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;

			if (lsr & UART_LSR_THRE)

				serial8250_tx_chars(up);

		}
@@ -2002,8 +1998,7 @@ static unsigned int serial8250_tx_empty(struct uart_port *port) 
	serial8250_rpm_get(up);



	spin_lock_irqsave(&port->lock, flags);

	lsr = serial_port_in(port, UART_LSR);

	up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;

	lsr = serial_lsr_in(up);

	spin_unlock_irqrestore(&port->lock, flags);



	serial8250_rpm_put(up);
@@ -2079,9 +2074,7 @@ static void wait_for_lsr(struct uart_8250_port *up, int bits) 


	/* Wait up to 10ms for the character(s) to be sent. */

	for (;;) {

		status = serial_in(up, UART_LSR);



		up->lsr_saved_flags |= status & LSR_SAVE_FLAGS;

		status = serial_lsr_in(up);



		if ((status & bits) == bits)

			break;