From bdb70c424df1543bc02ee2639aecebd20318c599 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ilpo=20J=C3=A4rvinen?= Date: Wed, 8 Jun 2022 12:54:27 +0300 Subject: [PATCH] serial: 8250: Create serial_lsr_in() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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: Andy Shevchenko Signed-off-by: Ilpo Järvinen Link: https://lore.kernel.org/r/20220608095431.18376-3-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250.h | 20 ++++++++++++++++++++ drivers/tty/serial/8250/8250_core.c | 3 +-- drivers/tty/serial/8250/8250_port.c | 15 ++++----------- 3 files changed, 25 insertions(+), 13 deletions(-) diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h index 696030cfcb09..c89cb881d9b0 100644 --- a/drivers/tty/serial/8250/8250.h +++ b/drivers/tty/serial/8250/8250.h @@ -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 */ diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index cfbd2de0ca6e..b0320de3379c 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -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)) { diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 209ecb1f29ed..5a5e81dd3b74 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -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; -- 2.11.0