From: Ilpo Järvinen ilpo.jarvinen@linux.intel.com
[ Upstream commit bdb70c424df1543bc02ee2639aecebd20318c599 ]
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 andy.shevchenko@gmail.com Signed-off-by: Ilpo Järvinen ilpo.jarvinen@linux.intel.com Link: https://lore.kernel.org/r/20220608095431.18376-3-ilpo.jarvinen@linux.intel.c... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 3f56dbc9432b..82726cda6066 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -277,8 +277,7 @@ 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 3c36a06a20b0..c9d8c0de56e5 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1514,11 +1514,9 @@ 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; /* @@ -1573,10 +1571,8 @@ 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); } @@ -2007,8 +2003,7 @@ 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); @@ -2084,9 +2079,7 @@ 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;