From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Rautkoski Kimmo EXT <ext-kimmo.rautkoski@vaisala.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Sasha Levin <sashal@kernel.org>,
linux-serial@vger.kernel.org
Subject: [PATCH AUTOSEL 4.14 14/60] serial: 8250: Fix TX interrupt handling condition
Date: Fri, 19 Jul 2019 00:10:23 -0400 [thread overview]
Message-ID: <20190719041109.18262-14-sashal@kernel.org> (raw)
In-Reply-To: <20190719041109.18262-1-sashal@kernel.org>
From: Rautkoski Kimmo EXT <ext-kimmo.rautkoski@vaisala.com>
[ Upstream commit db1b5bc047b3cadaedab3826bba82c3d9e023c4b ]
Interrupt handler checked THRE bit (transmitter holding register
empty) in LSR to detect if TX fifo is empty.
In case when there is only receive interrupts the TX handling
got called because THRE bit in LSR is set when there is no
transmission (FIFO empty). TX handling caused TX stop, which in
RS-485 half-duplex mode actually resets receiver FIFO. This is not
desired during reception because of possible data loss.
The fix is to check if THRI is set in IER in addition of the TX
fifo status. THRI in IER is set when TX is started and cleared
when TX is stopped.
This ensures that TX handling is only called when there is really
transmission on going and an interrupt for THRE and not when there
are only RX interrupts.
Signed-off-by: Kimmo Rautkoski <ext-kimmo.rautkoski@vaisala.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/tty/serial/8250/8250_port.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index ecf3d631bc09..b61fa5fcae68 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1879,7 +1879,8 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
status = serial8250_rx_chars(up, status);
}
serial8250_modem_status(up);
- if ((!up->dma || up->dma->tx_err) && (status & UART_LSR_THRE))
+ if ((!up->dma || up->dma->tx_err) && (status & UART_LSR_THRE) &&
+ (up->ier & UART_IER_THRI))
serial8250_tx_chars(up);
spin_unlock_irqrestore(&port->lock, flags);
--
2.20.1
next prev parent reply other threads:[~2019-07-19 4:10 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190719041109.18262-1-sashal@kernel.org>
2019-07-19 4:10 ` [PATCH AUTOSEL 4.14 03/60] tty: max310x: Fix invalid baudrate divisors calculator Sasha Levin
2019-07-19 4:10 ` [PATCH AUTOSEL 4.14 05/60] tty: serial: cpm_uart - fix init when SMC is relocated Sasha Levin
2019-07-19 4:10 ` [PATCH AUTOSEL 4.14 12/60] tty/serial: digicolor: Fix digicolor-usart already registered warning Sasha Levin
2019-07-19 4:10 ` [PATCH AUTOSEL 4.14 13/60] tty: serial: msm_serial: avoid system lockup condition Sasha Levin
2019-07-19 4:10 ` Sasha Levin [this message]
2019-07-19 4:10 ` [PATCH AUTOSEL 4.14 20/60] tty: serial_core: Set port active bit in uart_port_activate Sasha Levin
2019-07-19 4:10 ` [PATCH AUTOSEL 4.14 25/60] serial: mctrl_gpio: Check if GPIO property exisits before requesting it Sasha Levin
2019-07-19 4:10 ` [PATCH AUTOSEL 4.14 39/60] serial: sh-sci: Terminate TX DMA during buffer flushing Sasha Levin
2019-07-19 4:10 ` [PATCH AUTOSEL 4.14 40/60] serial: sh-sci: Fix TX DMA buffer flushing and workqueue races Sasha Levin
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