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Message-Id: <20220124071430.14907-8-jslaby@suse.cz>
Date: Mon, 24 Jan 2022 08:14:26 +0100
From: Jiri Slaby <jslaby@...e.cz>
To: gregkh@...uxfoundation.org
Cc: linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
johan@...nel.org, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 07/11] mxser: switch from xmit_buf to kfifo
Use kfifo for xmit buffer handling. The change is mostly
straightforward. It saves complexity both on the stuffing side
(mxser_write() and mxser_put_char()) and pulling side
(mxser_transmit_chars()). In fact, the loop in mxser_write() can be
completely deleted as the wrap of the buffer is taken care of in the
kfifo code now.
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
drivers/tty/mxser.c | 74 +++++++++++++++++----------------------------
1 file changed, 27 insertions(+), 47 deletions(-)
diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
index 4ddc12a63666..836c9eca2946 100644
--- a/drivers/tty/mxser.c
+++ b/drivers/tty/mxser.c
@@ -275,9 +275,6 @@ struct mxser_port {
u8 read_status_mask;
u8 ignore_status_mask;
u8 xmit_fifo_size;
- unsigned int xmit_head;
- unsigned int xmit_tail;
- unsigned int xmit_cnt;
spinlock_t slock;
};
@@ -813,7 +810,7 @@ static int mxser_activate(struct tty_port *port, struct tty_struct *tty)
(void) inb(info->ioaddr + UART_MSR);
clear_bit(TTY_IO_ERROR, &tty->flags);
- info->xmit_cnt = info->xmit_head = info->xmit_tail = 0;
+ kfifo_reset(&port->xmit_fifo);
/*
* and set the speed of the serial port
@@ -901,9 +898,8 @@ static void mxser_flush_buffer(struct tty_struct *tty)
struct mxser_port *info = tty->driver_data;
unsigned long flags;
-
spin_lock_irqsave(&info->slock, flags);
- info->xmit_cnt = info->xmit_head = info->xmit_tail = 0;
+ kfifo_reset(&info->port.xmit_fifo);
outb(info->FCR | UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
info->ioaddr + UART_FCR);
@@ -920,50 +916,34 @@ static void mxser_close(struct tty_struct *tty, struct file *filp)
static int mxser_write(struct tty_struct *tty, const unsigned char *buf, int count)
{
- int c, total = 0;
struct mxser_port *info = tty->driver_data;
unsigned long flags;
+ int written;
+ bool is_empty;
- while (1) {
- c = min_t(int, count, min(SERIAL_XMIT_SIZE - info->xmit_cnt - 1,
- SERIAL_XMIT_SIZE - info->xmit_head));
- if (c <= 0)
- break;
-
- memcpy(info->port.xmit_buf + info->xmit_head, buf, c);
- spin_lock_irqsave(&info->slock, flags);
- info->xmit_head = (info->xmit_head + c) &
- (SERIAL_XMIT_SIZE - 1);
- info->xmit_cnt += c;
- spin_unlock_irqrestore(&info->slock, flags);
-
- buf += c;
- count -= c;
- total += c;
- }
+ spin_lock_irqsave(&info->slock, flags);
+ written = kfifo_in(&info->port.xmit_fifo, buf, count);
+ is_empty = kfifo_is_empty(&info->port.xmit_fifo);
+ spin_unlock_irqrestore(&info->slock, flags);
- if (info->xmit_cnt && !tty->flow.stopped)
+ if (!is_empty && !tty->flow.stopped)
if (!tty->hw_stopped || mxser_16550A_or_MUST(info))
mxser_start_tx(info);
- return total;
+ return written;
}
static int mxser_put_char(struct tty_struct *tty, unsigned char ch)
{
struct mxser_port *info = tty->driver_data;
unsigned long flags;
-
- if (info->xmit_cnt >= SERIAL_XMIT_SIZE - 1)
- return 0;
+ int ret;
spin_lock_irqsave(&info->slock, flags);
- info->port.xmit_buf[info->xmit_head++] = ch;
- info->xmit_head &= SERIAL_XMIT_SIZE - 1;
- info->xmit_cnt++;
+ ret = kfifo_put(&info->port.xmit_fifo, ch);
spin_unlock_irqrestore(&info->slock, flags);
- return 1;
+ return ret;
}
@@ -971,7 +951,7 @@ static void mxser_flush_chars(struct tty_struct *tty)
{
struct mxser_port *info = tty->driver_data;
- if (!info->xmit_cnt || tty->flow.stopped ||
+ if (kfifo_is_empty(&info->port.xmit_fifo) || tty->flow.stopped ||
(tty->hw_stopped && !mxser_16550A_or_MUST(info)))
return;
@@ -981,16 +961,15 @@ static void mxser_flush_chars(struct tty_struct *tty)
static unsigned int mxser_write_room(struct tty_struct *tty)
{
struct mxser_port *info = tty->driver_data;
- int ret;
- ret = SERIAL_XMIT_SIZE - info->xmit_cnt - 1;
- return ret < 0 ? 0 : ret;
+ return kfifo_avail(&info->port.xmit_fifo);
}
static unsigned int mxser_chars_in_buffer(struct tty_struct *tty)
{
struct mxser_port *info = tty->driver_data;
- return info->xmit_cnt;
+
+ return kfifo_len(&info->port.xmit_fifo);
}
/*
@@ -1379,7 +1358,7 @@ static void mxser_start(struct tty_struct *tty)
unsigned long flags;
spin_lock_irqsave(&info->slock, flags);
- if (info->xmit_cnt)
+ if (!kfifo_is_empty(&info->port.xmit_fifo))
__mxser_start_tx(info);
spin_unlock_irqrestore(&info->slock, flags);
}
@@ -1610,7 +1589,7 @@ static void mxser_transmit_chars(struct tty_struct *tty, struct mxser_port *port
return;
}
- if (!port->xmit_cnt || tty->flow.stopped ||
+ if (kfifo_is_empty(&port->port.xmit_fifo) || tty->flow.stopped ||
(tty->hw_stopped && !mxser_16550A_or_MUST(port))) {
__mxser_stop_tx(port);
return;
@@ -1618,18 +1597,19 @@ static void mxser_transmit_chars(struct tty_struct *tty, struct mxser_port *port
count = port->xmit_fifo_size;
do {
- outb(port->port.xmit_buf[port->xmit_tail++],
- port->ioaddr + UART_TX);
- port->xmit_tail &= SERIAL_XMIT_SIZE - 1;
- port->icount.tx++;
- if (!--port->xmit_cnt)
+ unsigned char c;
+
+ if (!kfifo_get(&port->port.xmit_fifo, &c))
break;
+
+ outb(c, port->ioaddr + UART_TX);
+ port->icount.tx++;
} while (--count > 0);
- if (port->xmit_cnt < WAKEUP_CHARS)
+ if (kfifo_len(&port->port.xmit_fifo) < WAKEUP_CHARS)
tty_wakeup(tty);
- if (!port->xmit_cnt)
+ if (kfifo_is_empty(&port->port.xmit_fifo))
__mxser_stop_tx(port);
}
--
2.34.1
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