serial: sh-sci: Fix unlocked access to SCSCR register

The SCSCR register access in sci_break_ctl() is not locked.

sci_start_tx() and sci_set_termios() changes the SCSCR register,
but does not lock sci_port.

Therefore, this patch adds lock during register access.

Also, remove the log output that leads to a double lock.

Some analysis of where locks are not taken is as follows.
It appears that the lock is not taken in:
  - sci_start_tx(), sci_stop_tx()  as this is installed as a callback.
    And all callers of the callback take the lock.
  - start_rx as callers take the lock.
  - stop_rx. this is both installed as a callback and called directly.
    In both cases the caller takes the lock.

Signed-off-by: Takatoshi Akiyama <takatoshi.akiyama.kj@ps.hitachi-solutions.com>
Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index d5714de..d5e07dd 100644 (file)
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -1226,8 +1226,11 @@ static void sci_rx_dma_release(struct sci_port *s, bool enable_pio)
        dma_free_coherent(chan->device->dev, s->buf_len_rx * 2, s->rx_buf[0],
                          sg_dma_address(&s->sg_rx[0]));
        dma_release_channel(chan);
-       if (enable_pio)
+       if (enable_pio) {
+               spin_lock_irqsave(&port->lock, flags);
                sci_start_rx(port);
+               spin_unlock_irqrestore(&port->lock, flags);
+       }
 }
 
 static void sci_dma_rx_complete(void *arg)
@@ -1294,8 +1297,11 @@ static void sci_tx_dma_release(struct sci_port *s, bool enable_pio)
        dma_unmap_single(chan->device->dev, s->tx_dma_addr, UART_XMIT_SIZE,
                         DMA_TO_DEVICE);
        dma_release_channel(chan);
-       if (enable_pio)
+       if (enable_pio) {
+               spin_lock_irqsave(&port->lock, flags);
                sci_start_tx(port);
+               spin_unlock_irqrestore(&port->lock, flags);
+       }
 }
 
 static void sci_submit_rx(struct sci_port *s)
@@ -2004,6 +2010,7 @@ static void sci_enable_ms(struct uart_port *port)
 static void sci_break_ctl(struct uart_port *port, int break_state)
 {
        unsigned short scscr, scsptr;
+       unsigned long flags;
 
        /* check wheter the port has SCSPTR */
        if (!sci_getreg(port, SCSPTR)->size) {
@@ -2014,6 +2021,7 @@ static void sci_break_ctl(struct uart_port *port, int break_state)
                return;
        }
 
+       spin_lock_irqsave(&port->lock, flags);
        scsptr = serial_port_in(port, SCSPTR);
        scscr = serial_port_in(port, SCSCR);
 
@@ -2027,6 +2035,7 @@ static void sci_break_ctl(struct uart_port *port, int break_state)
 
        serial_port_out(port, SCSPTR, scsptr);
        serial_port_out(port, SCSCR, scscr);
+       spin_unlock_irqrestore(&port->lock, flags);
 }
 
 static int sci_startup(struct uart_port *port)
@@ -2255,6 +2264,7 @@ static void sci_set_termios(struct uart_port *port, struct ktermios *termios,
        int min_err = INT_MAX, err;
        unsigned long max_freq = 0;
        int best_clk = -1;
+       unsigned long flags;
 
        if ((termios->c_cflag & CSIZE) == CS7)
                smr_val |= SCSMR_CHR;
@@ -2364,6 +2374,8 @@ done:
                serial_port_out(port, SCCKS, sccks);
        }
 
+       spin_lock_irqsave(&port->lock, flags);
+
        sci_reset(port);
 
        uart_update_timeout(port, termios->c_cflag, baud);
@@ -2381,9 +2393,6 @@ done:
                        case 27: smr_val |= SCSMR_SRC_27; break;
                        }
                smr_val |= cks;
-               dev_dbg(port->dev,
-                        "SCR 0x%x SMR 0x%x BRR %u CKS 0x%x DL %u SRR %u\n",
-                        scr_val, smr_val, brr, sccks, dl, srr);
                serial_port_out(port, SCSCR, scr_val | s->hscif_tot);
                serial_port_out(port, SCSMR, smr_val);
                serial_port_out(port, SCBRR, brr);
@@ -2397,7 +2406,6 @@ done:
                scr_val = s->cfg->scscr & (SCSCR_CKE1 | SCSCR_CKE0);
                smr_val |= serial_port_in(port, SCSMR) &
                           (SCSMR_CKEDG | SCSMR_SRC_MASK | SCSMR_CKS);
-               dev_dbg(port->dev, "SCR 0x%x SMR 0x%x\n", scr_val, smr_val);
                serial_port_out(port, SCSCR, scr_val | s->hscif_tot);
                serial_port_out(port, SCSMR, smr_val);
        }
@@ -2434,7 +2442,6 @@ done:
 
        scr_val |= SCSCR_RE | SCSCR_TE |
                   (s->cfg->scscr & ~(SCSCR_CKE1 | SCSCR_CKE0));
-       dev_dbg(port->dev, "SCSCR 0x%x\n", scr_val);
        serial_port_out(port, SCSCR, scr_val | s->hscif_tot);
        if ((srr + 1 == 5) &&
            (port->type == PORT_SCIFA || port->type == PORT_SCIFB)) {
@@ -2481,8 +2488,6 @@ done:
        s->rx_frame = (100 * bits * HZ) / (baud / 10);
 #ifdef CONFIG_SERIAL_SH_SCI_DMA
        s->rx_timeout = DIV_ROUND_UP(s->buf_len_rx * 2 * s->rx_frame, 1000);
-       dev_dbg(port->dev, "DMA Rx t-out %ums, tty t-out %u jiffies\n",
-               s->rx_timeout * 1000 / HZ, port->timeout);
        if (s->rx_timeout < msecs_to_jiffies(20))
                s->rx_timeout = msecs_to_jiffies(20);
 #endif
@@ -2490,6 +2495,8 @@ done:
        if ((termios->c_cflag & CREAD) != 0)
                sci_start_rx(port);
 
+       spin_unlock_irqrestore(&port->lock, flags);
+
        sci_port_disable(s);
 
        if (UART_ENABLE_MS(port, termios->c_cflag))