jsm: remove buggy write queue

jsm uses a write queue that copies from uart_core circular buffer. This
copying however has some bugs, like not wrapping the head counter. Since
this write queue is also a circular buffer, the consumer function is
ready to use the uart_core circular buffer directly.

This buggy copying function was making some bytes be dropped when
transmitting to a raw tty, doing something like this.

[root@hostname ~]$ cat /dev/ttyn1 > cascardo/dump &
[1] 2658
[root@hostname ~]$ cat /proc/tty/drivers > /dev/ttyn0
[root@hostname ~]$ cat /proc/tty/drivers
/dev/tty             /dev/tty        5       0 system:/dev/tty
/dev/console         /dev/console    5       1 system:console
/dev/ptmx            /dev/ptmx       5       2 system
/dev/vc/0            /dev/vc/0       4       0 system:vtmaster
jsm                  /dev/ttyn     250 0-31 serial
serial               /dev/ttyS       4 64-95 serial
hvc                  /dev/hvc      229 0-7 system
pty_slave            /dev/pts      136 0-1048575 pty:slave
pty_master           /dev/ptm      128 0-1048575 pty:master
unknown              /dev/tty        4 1-63 console
[root@hostname ~]$ cat cascardo/dump
/dev/tty             /dev/tty        5       0 system:/dev/tty
/dev/console         /dev/console    5       1 system:console
/dev/ptmx            /dev/ptmx       5       2 system
/dev/vc/0            /dev/vc/0       4       0 system:vtmaste[root@hostname ~]$

This patch drops the driver write queue entirely, using the circular
buffer from uart_core only.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 15 insertions, 14 deletions

diff --git a/drivers/tty/serial/jsm/jsm_neo.c b/drivers/tty/serial/jsm/jsm_neo.c
index 4538c3e3646e..bd6e84699e11 100644
--- a/drivers/tty/serial/jsm/jsm_neo.c
+++ b/drivers/tty/serial/jsm/jsm_neo.c
@@ -496,12 +496,15 @@ static void neo_copy_data_from_queue_to_uart(struct jsm_channel *ch)
 	int s;
 	int qlen;
 	u32 len_written = 0;
+	struct circ_buf *circ;
 
 	if (!ch)
 		return;
 
+	circ = &ch->uart_port.state->xmit;
+
 	/* No data to write to the UART */
-	if (ch->ch_w_tail == ch->ch_w_head)
+	if (uart_circ_empty(circ))
 		return;
 
 	/* If port is "stopped", don't send any data to the UART */
@@ -517,11 +520,10 @@ static void neo_copy_data_from_queue_to_uart(struct jsm_channel *ch)
 		if (ch->ch_cached_lsr & UART_LSR_THRE) {
 			ch->ch_cached_lsr &= ~(UART_LSR_THRE);
 
-			writeb(ch->ch_wqueue[ch->ch_w_tail], &ch->ch_neo_uart->txrx);
+			writeb(circ->buf[circ->tail], &ch->ch_neo_uart->txrx);
 			jsm_printk(WRITE, INFO, &ch->ch_bd->pci_dev,
-					"Tx data: %x\n", ch->ch_wqueue[ch->ch_w_head]);
-			ch->ch_w_tail++;
-			ch->ch_w_tail &= WQUEUEMASK;
+					"Tx data: %x\n", circ->buf[circ->head]);
+			circ->tail = (circ->tail + 1) & (UART_XMIT_SIZE - 1);
 			ch->ch_txcount++;
 		}
 		return;
@@ -536,36 +538,36 @@ static void neo_copy_data_from_queue_to_uart(struct jsm_channel *ch)
 	n = UART_17158_TX_FIFOSIZE - ch->ch_t_tlevel;
 
 	/* cache head and tail of queue */
-	head = ch->ch_w_head & WQUEUEMASK;
-	tail = ch->ch_w_tail & WQUEUEMASK;
-	qlen = (head - tail) & WQUEUEMASK;
+	head = circ->head & (UART_XMIT_SIZE - 1);
+	tail = circ->tail & (UART_XMIT_SIZE - 1);
+	qlen = uart_circ_chars_pending(circ);
 
 	/* Find minimum of the FIFO space, versus queue length */
 	n = min(n, qlen);
 
 	while (n > 0) {
 
-		s = ((head >= tail) ? head : WQUEUESIZE) - tail;
+		s = ((head >= tail) ? head : UART_XMIT_SIZE) - tail;
 		s = min(s, n);
 
 		if (s <= 0)
 			break;
 
-		memcpy_toio(&ch->ch_neo_uart->txrxburst, ch->ch_wqueue + tail, s);
+		memcpy_toio(&ch->ch_neo_uart->txrxburst, circ->buf + tail, s);
 		/* Add and flip queue if needed */
-		tail = (tail + s) & WQUEUEMASK;
+		tail = (tail + s) & (UART_XMIT_SIZE - 1);
 		n -= s;
 		ch->ch_txcount += s;
 		len_written += s;
 	}
 
 	/* Update the final tail */
-	ch->ch_w_tail = tail & WQUEUEMASK;
+	circ->tail = tail & (UART_XMIT_SIZE - 1);
 
 	if (len_written >= ch->ch_t_tlevel)
 		ch->ch_flags &= ~(CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);
 
-	if (!jsm_tty_write(&ch->uart_port))
+	if (uart_circ_empty(circ))
 		uart_write_wakeup(&ch->uart_port);
 }
 
@@ -946,7 +948,6 @@ static void neo_param(struct jsm_channel *ch)
 	if ((ch->ch_c_cflag & (CBAUD)) == 0) {
 		ch->ch_r_head = ch->ch_r_tail = 0;
 		ch->ch_e_head = ch->ch_e_tail = 0;
-		ch->ch_w_head = ch->ch_w_tail = 0;
 
 		neo_flush_uart_write(ch);
 		neo_flush_uart_read(ch);