serial: pl011: Do not clear RX FIFO & RX interrupt in unthrottle.

[ Upstream commit 032d5a71ed378ffc6a2d41a187d8488a4f9fe415 ]

Clearing the RX FIFO will cause data loss.
Copy the pl011_enabl_interrupts implementation, and remove the clear
interrupt and FIFO part of the code.

Fixes: 211565b10099 ("serial: pl011: UPSTAT_AUTORTS requires .throttle/unthrottle")
Signed-off-by: delisun <delisun@pateo.com.cn>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20221110020108.7700-1-delisun@pateo.com.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 5b97645..aa0bbb7 100644 (file)
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1831,8 +1831,17 @@ static void pl011_enable_interrupts(struct uart_amba_port *uap)
 static void pl011_unthrottle_rx(struct uart_port *port)
 {
        struct uart_amba_port *uap = container_of(port, struct uart_amba_port, port);
+       unsigned long flags;
 
-       pl011_enable_interrupts(uap);
+       spin_lock_irqsave(&uap->port.lock, flags);
+
+       uap->im = UART011_RTIM;
+       if (!pl011_dma_rx_running(uap))
+               uap->im |= UART011_RXIM;
+
+       pl011_write(uap->im, uap, REG_IMSC);
+
+       spin_unlock_irqrestore(&uap->port.lock, flags);
 }
 
 static int pl011_startup(struct uart_port *port)