serial: atmel_serial: drop low-latency workaround

Commit 1ecc26bd2789 ("atmel_serial: split the interrupt handler") worked
around the infamous low_latency behaviour of tty_flip_buffer_push() by
dropping and reacquiring the port lock in the tasklet callback.

Since commit a9c3f68f3cd8 ("tty: Fix low_latency BUG"),
tty_flip_buffer_push() always schedules a work item to push data to the
line discipline and there's no need to keep any low_latency hacks around.

Cc: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210421095509.3024-10-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index a24e5c2..058886d 100644 (file)
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -1178,13 +1178,7 @@ static void atmel_rx_from_dma(struct uart_port *port)
                               1,
                               DMA_FROM_DEVICE);
 
-       /*
-        * Drop the lock here since it might end up calling
-        * uart_start(), which takes the lock.
-        */
-       spin_unlock(&port->lock);
        tty_flip_buffer_push(tport);
-       spin_lock(&port->lock);
 
        atmel_uart_writel(port, ATMEL_US_IER, ATMEL_US_TIMEOUT);
 }
@@ -1576,13 +1570,7 @@ static void atmel_rx_from_ring(struct uart_port *port)
                uart_insert_char(port, status, ATMEL_US_OVRE, c.ch, flg);
        }
 
-       /*
-        * Drop the lock here since it might end up calling
-        * uart_start(), which takes the lock.
-        */
-       spin_unlock(&port->lock);
        tty_flip_buffer_push(&port->state->port);
-       spin_lock(&port->lock);
 }
 
 static void atmel_release_rx_pdc(struct uart_port *port)
@@ -1667,13 +1655,7 @@ static void atmel_rx_from_pdc(struct uart_port *port)
                }
        } while (head >= pdc->dma_size);
 
-       /*
-        * Drop the lock here since it might end up calling
-        * uart_start(), which takes the lock.
-        */
-       spin_unlock(&port->lock);
        tty_flip_buffer_push(tport);
-       spin_lock(&port->lock);
 
        atmel_uart_writel(port, ATMEL_US_IER,
                          ATMEL_US_ENDRX | ATMEL_US_TIMEOUT);