[PATCH 09/26] serial: atmel_serial: drop low-latency workaround

Johan Hovold
2021-04-21T09:55:54Z

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>
---
drivers/tty/serial/atmel_serial.c | 18 ------------------
1 file changed, 18 deletions(-)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index a24e5c2b30bc..058886d9045b 100644
--- 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);
--
2.26.3