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>

4 files changed, 28 insertions, 103 deletions

diff --git a/drivers/tty/serial/jsm/jsm.h b/drivers/tty/serial/jsm/jsm.h
index cd53bdda77c..529bec6edaf 100644
--- a/drivers/tty/serial/jsm/jsm.h
+++ b/drivers/tty/serial/jsm/jsm.h
@@ -180,10 +180,8 @@ struct jsm_board
 /* Our Read/Error/Write queue sizes */
 #define RQUEUEMASK      0x1FFF          /* 8 K - 1 */
 #define EQUEUEMASK      0x1FFF          /* 8 K - 1 */
-#define WQUEUEMASK      0x0FFF          /* 4 K - 1 */
 #define RQUEUESIZE      (RQUEUEMASK + 1)
 #define EQUEUESIZE      RQUEUESIZE
-#define WQUEUESIZE      (WQUEUEMASK + 1)
 
 
 /************************************************************************
@@ -223,10 +221,6 @@ struct jsm_channel {
         u16             ch_e_head;      /* Head location of the error queue */
         u16             ch_e_tail;      /* Tail location of the error queue */
 
-        u8              *ch_wqueue;     /* Our write queue buffer - malloc'ed */
-        u16             ch_w_head;      /* Head location of the write queue */
-        u16             ch_w_tail;      /* Tail location of the write queue */
-
         u64             ch_rxcount;     /* total of data received so far */
         u64             ch_txcount;     /* total of data transmitted so far */
 
@@ -375,7 +369,6 @@ extern int	jsm_debug;
  * Prototypes for non-static functions used in more than one module
  *
  *************************************************************************/
-int jsm_tty_write(struct uart_port *port);
 int jsm_tty_init(struct jsm_board *);
 int jsm_uart_port_init(struct jsm_board *);
 int jsm_remove_uart_port(struct jsm_board *);
diff --git a/drivers/tty/serial/jsm/jsm_driver.c b/drivers/tty/serial/jsm/jsm_driver.c
index 1cc8cf602af..648b6a3efa3 100644
--- a/drivers/tty/serial/jsm/jsm_driver.c
+++ b/drivers/tty/serial/jsm/jsm_driver.c
@@ -194,7 +194,6 @@ static void __devexit jsm_remove_one(struct pci_dev *pdev)
                 if (brd->channels[i]) {
                         kfree(brd->channels[i]->ch_rqueue);
                         kfree(brd->channels[i]->ch_equeue);
-                        kfree(brd->channels[i]->ch_wqueue);
                         kfree(brd->channels[i]);
                 }
         }
diff --git a/drivers/tty/serial/jsm/jsm_neo.c b/drivers/tty/serial/jsm/jsm_neo.c
index 4538c3e3646..bd6e84699e1 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);
diff --git a/drivers/tty/serial/jsm/jsm_tty.c b/drivers/tty/serial/jsm/jsm_tty.c
index 7a4a914ecff..434bd881fca 100644
--- a/drivers/tty/serial/jsm/jsm_tty.c
+++ b/drivers/tty/serial/jsm/jsm_tty.c
@@ -118,6 +118,19 @@ static void jsm_tty_set_mctrl(struct uart_port *port, unsigned int mctrl)
         udelay(10);
 }
 
+/*
+ * jsm_tty_write()
+ *
+ * Take data from the user or kernel and send it out to the FEP.
+ * In here exists all the Transparent Print magic as well.
+ */
+static void jsm_tty_write(struct uart_port *port)
+{
+        struct jsm_channel *channel;
+        channel = container_of(port, struct jsm_channel, uart_port);
+        channel->ch_bd->bd_ops->copy_data_from_queue_to_uart(channel);
+}
+
 static void jsm_tty_start_tx(struct uart_port *port)
 {
         struct jsm_channel *channel = (struct jsm_channel *)port;
@@ -216,14 +229,6 @@ static int jsm_tty_open(struct uart_port *port)
                         return -ENOMEM;
                 }
         }
-        if (!channel->ch_wqueue) {
-                channel->ch_wqueue = kzalloc(WQUEUESIZE, GFP_KERNEL);
-                if (!channel->ch_wqueue) {
-                        jsm_printk(INIT, ERR, &channel->ch_bd->pci_dev,
-                                "unable to allocate write queue buf");
-                        return -ENOMEM;
-                }
-        }
 
         channel->ch_flags &= ~(CH_OPENING);
         /*
@@ -237,7 +242,6 @@ static int jsm_tty_open(struct uart_port *port)
          */
         channel->ch_r_head = channel->ch_r_tail = 0;
         channel->ch_e_head = channel->ch_e_tail = 0;
-        channel->ch_w_head = channel->ch_w_tail = 0;
 
         brd->bd_ops->flush_uart_write(channel);
         brd->bd_ops->flush_uart_read(channel);
@@ -836,75 +840,3 @@ void jsm_check_queue_flow_control(struct jsm_channel *ch)
                 }
         }
 }
-
-/*
- * jsm_tty_write()
- *
- * Take data from the user or kernel and send it out to the FEP.
- * In here exists all the Transparent Print magic as well.
- */
-int jsm_tty_write(struct uart_port *port)
-{
-        int bufcount;
-        int data_count = 0,data_count1 =0;
-        u16 head;
-        u16 tail;
-        u16 tmask;
-        u32 remain;
-        int temp_tail = port->state->xmit.tail;
-        struct jsm_channel *channel = (struct jsm_channel *)port;
-
-        tmask = WQUEUEMASK;
-        head = (channel->ch_w_head) & tmask;
-        tail = (channel->ch_w_tail) & tmask;
-
-        if ((bufcount = tail - head - 1) < 0)
-                bufcount += WQUEUESIZE;
-
-        bufcount = min(bufcount, 56);
-        remain = WQUEUESIZE - head;
-
-        data_count = 0;
-        if (bufcount >= remain) {
-                bufcount -= remain;
-                while ((port->state->xmit.head != temp_tail) &&
-                (data_count < remain)) {
-                        channel->ch_wqueue[head++] =
-                        port->state->xmit.buf[temp_tail];
-
-                        temp_tail++;
-                        temp_tail &= (UART_XMIT_SIZE - 1);
-                        data_count++;
-                }
-                if (data_count == remain) head = 0;
-        }
-
-        data_count1 = 0;
-        if (bufcount > 0) {
-                remain = bufcount;
-                while ((port->state->xmit.head != temp_tail) &&
-                        (data_count1 < remain)) {
-                        channel->ch_wqueue[head++] =
-                                port->state->xmit.buf[temp_tail];
-
-                        temp_tail++;
-                        temp_tail &= (UART_XMIT_SIZE - 1);
-                        data_count1++;
-
-                }
-        }
-
-        port->state->xmit.tail = temp_tail;
-
-        data_count += data_count1;
-        if (data_count) {
-                head &= tmask;
-                channel->ch_w_head = head;
-        }
-
-        if (data_count) {
-                channel->ch_bd->bd_ops->copy_data_from_queue_to_uart(channel);
-        }
-
-        return data_count;
-}