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author | Anssi Hannula <anssi.hannula@bitwise.fi> | 2019-02-15 17:45:08 +0100 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-02-19 13:42:07 +0100 |
commit | 7abab1605139bc41442864c18f9573440f7ca105 (patch) | |
tree | 1bdafd100c06297dfc856254514a6b9dcff8a77c /drivers/tty | |
parent | tty: serial: remove redundant likely annotation (diff) | |
download | linux-7abab1605139bc41442864c18f9573440f7ca105.tar.xz linux-7abab1605139bc41442864c18f9573440f7ca105.zip |
serial: uartps: Fix stuck ISR if RX disabled with non-empty FIFO
If RX is disabled while there are still unprocessed bytes in RX FIFO,
cdns_uart_handle_rx() called from interrupt handler will get stuck in
the receive loop as read bytes will not get removed from the RX FIFO
and CDNS_UART_SR_RXEMPTY bit will never get set.
Avoid the stuck handler by checking first if RX is disabled. port->lock
protects against race with RX-disabling functions.
This HW behavior was mentioned by Nathan Rossi in 43e98facc4a3 ("tty:
xuartps: Fix RX hang, and TX corruption in termios call") which fixed a
similar issue in cdns_uart_set_termios().
The behavior can also be easily verified by e.g. setting
CDNS_UART_CR_RX_DIS at the beginning of cdns_uart_handle_rx() - the
following loop will then get stuck.
Resetting the FIFO using RXRST would not set RXEMPTY either so simply
issuing a reset after RX-disable would not work.
I observe this frequently on a ZynqMP board during heavy RX load at 1M
baudrate when the reader process exits and thus RX gets disabled.
Fixes: 61ec9016988f ("tty/serial: add support for Xilinx PS UART")
Signed-off-by: Anssi Hannula <anssi.hannula@bitwise.fi>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
-rw-r--r-- | drivers/tty/serial/xilinx_uartps.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c index 094f2958cb2b..ee9f18c52d29 100644 --- a/drivers/tty/serial/xilinx_uartps.c +++ b/drivers/tty/serial/xilinx_uartps.c @@ -364,7 +364,13 @@ static irqreturn_t cdns_uart_isr(int irq, void *dev_id) cdns_uart_handle_tx(dev_id); isrstatus &= ~CDNS_UART_IXR_TXEMPTY; } - if (isrstatus & CDNS_UART_IXR_RXMASK) + + /* + * Skip RX processing if RX is disabled as RXEMPTY will never be set + * as read bytes will not be removed from the FIFO. + */ + if (isrstatus & CDNS_UART_IXR_RXMASK && + !(readl(port->membase + CDNS_UART_CR) & CDNS_UART_CR_RX_DIS)) cdns_uart_handle_rx(dev_id, isrstatus); spin_unlock(&port->lock); |