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Subject[PATCH 19/25] serial: timbuart: make sure last byte is sent when port is closed
Date
From: Richard Röjfors <richard.rojfors@pelagicore.com>

Fix a problem in early versions of the FPGA IP.

In certain situations the IP reports that the FIFO is empty, but a byte is
still clocked out. If a flush is done at that point the currently clocked
byte is canceled.

This causes incompatibilities with the upper layers when a port is closed,
it waits until the FIFO is empty and then closes the port. During close
the FIFO is flushed -> the last byte is not sent properly.

Now the FIFO is only flushed if it is reported to be non-empty. Which
makes the currently clocked out byte to finish.

[akpm@linux-foundation.org: fix build]
Signed-off-by: Richard Röjfors <richard.rojfors@pelagicore.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
drivers/serial/timbuart.c | 23 +++++++++++++----------
1 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/serial/timbuart.c b/drivers/serial/timbuart.c
index 62f389f..67ca642 100644
--- a/drivers/serial/timbuart.c
+++ b/drivers/serial/timbuart.c
@@ -68,12 +68,22 @@ static void timbuart_start_tx(struct uart_port *port)
tasklet_schedule(&uart->tasklet);
}

+static unsigned int timbuart_tx_empty(struct uart_port *port)
+{
+ u32 isr = ioread32(port->membase + TIMBUART_ISR);
+
+ return (isr & TXBE) ? TIOCSER_TEMT : 0;
+}
+
static void timbuart_flush_buffer(struct uart_port *port)
{
- u8 ctl = ioread8(port->membase + TIMBUART_CTRL) | TIMBUART_CTRL_FLSHTX;
+ if (!timbuart_tx_empty(port)) {
+ u8 ctl = ioread8(port->membase + TIMBUART_CTRL) |
+ TIMBUART_CTRL_FLSHTX;

- iowrite8(ctl, port->membase + TIMBUART_CTRL);
- iowrite32(TXBF, port->membase + TIMBUART_ISR);
+ iowrite8(ctl, port->membase + TIMBUART_CTRL);
+ iowrite32(TXBF, port->membase + TIMBUART_ISR);
+ }
}

static void timbuart_rx_chars(struct uart_port *port)
@@ -195,13 +205,6 @@ void timbuart_tasklet(unsigned long arg)
dev_dbg(uart->port.dev, "%s leaving\n", __func__);
}

-static unsigned int timbuart_tx_empty(struct uart_port *port)
-{
- u32 isr = ioread32(port->membase + TIMBUART_ISR);
-
- return (isr & TXBE) ? TIOCSER_TEMT : 0;
-}
-
static unsigned int timbuart_get_mctrl(struct uart_port *port)
{
u8 cts = ioread8(port->membase + TIMBUART_CTRL);
--
1.7.0.3
--
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