+ Shubhrajyoti
On 06. 02. 19 15:08, Anssi Hannula wrote:
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
drivers/tty/serial/xilinx_uartps.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c index 094f2958cb2b..f0c4f59d9314 100644 --- a/drivers/tty/serial/xilinx_uartps.c +++ b/drivers/tty/serial/xilinx_uartps.c @@ -219,6 +219,13 @@ static void cdns_uart_handle_rx(void *dev_id, unsigned int isrstatus) is_rxbs_support = cdns_uart->quirks & CDNS_UART_RXBS_SUPPORT;
- /*
* RXEMPTY will never be set if RX is disabled as read bytes* will not be removed from the FIFO*/- if (readl(port->membase + CDNS_UART_CR) & CDNS_UART_CR_RX_DIS)
return;- while ((readl(port->membase + CDNS_UART_SR) & CDNS_UART_SR_RXEMPTY) != CDNS_UART_SR_RXEMPTY) { if (is_rxbs_support)
Please review. M