The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From abeb2e9414d7e3a0d8417bc3b13d7172513ea8a0 Mon Sep 17 00:00:00 2001

From: Yonghan Ye yonghan.ye@unisoc.com Date: Wed, 4 Dec 2019 20:00:07 +0800 Subject: [PATCH] serial: sprd: Add clearing break interrupt operation

A break interrupt will be generated if the RX line was pulled low, which means some abnomal behaviors occurred of the UART. In this case, we still need to clear this break interrupt status, otherwise it will cause irq storm to crash the whole system.

Fixes: b7396a38fb28 ("tty/serial: Add Spreadtrum sc9836-uart driver support") Signed-off-by: Yonghan Ye yonghan.ye@unisoc.com Cc: stable stable@vger.kernel.org Signed-off-by: Baolin Wang baolin.wang7@gmail.com Link: https://lore.kernel.org/r/925e51b73099c90158e080b8f5bed9b3b38c4548.157546060... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c index 31df23502562..f60a59d9bf27 100644 --- a/drivers/tty/serial/sprd_serial.c +++ b/drivers/tty/serial/sprd_serial.c @@ -679,6 +679,9 @@ static irqreturn_t sprd_handle_irq(int irq, void *dev_id) if (ims & SPRD_IMSR_TIMEOUT) serial_out(port, SPRD_ICLR, SPRD_ICLR_TIMEOUT);

+ if (ims & SPRD_IMSR_BREAK_DETECT) + serial_out(port, SPRD_ICLR, SPRD_IMSR_BREAK_DETECT); + if (ims & (SPRD_IMSR_RX_FIFO_FULL | SPRD_IMSR_BREAK_DETECT | SPRD_IMSR_TIMEOUT)) sprd_rx(port);