4.9-stable review patch. If anyone has any objections, please let me know.
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From: Vignesh R vigneshr@ti.com
[ Upstream commit 2e9fe539108320820016f78ca7704a7342788380 ]
Currently, data in RX FIFO is read based on UART_LSR register state even if RDI and RLSI interrupts are disabled in UART_IER register. This is because when IRQ handler is called due to TX FIFO empty event, RX FIFO is serviced based on UART_LSR register status instead of UART_IIR status. This defeats the purpose of disabling UART RX FIFO interrupts during throttling(see, omap_8250_throttle()) as IRQ handler continues to drain UART RX FIFO resulting in overflow of buffer at tty layer. Fix this by making sure that driver drains UART RX FIFO only when UART_IIR_RDI is set along with UART_LSR_BI or UART_LSR_DR bits.
Signed-off-by: Vignesh R vigneshr@ti.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/serial/8250/8250_port.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1815,7 +1815,8 @@ int serial8250_handle_irq(struct uart_po
status = serial_port_in(port, UART_LSR);
- if (status & (UART_LSR_DR | UART_LSR_BI)) { + if (status & (UART_LSR_DR | UART_LSR_BI) && + iir & UART_IIR_RDI) { if (!up->dma || handle_rx_dma(up, iir)) status = serial8250_rx_chars(up, status); }