serial: sh-sci: Get rid of the workqueue to handle receive DMA requests

The receive DMA workqueue function work_fn_rx() handles two things:
  1. Reception of a full buffer on completion of a receive DMA request,
  2. Reception of a partial buffer on receive DMA time-out.
The workqueue is kicked by both the receive DMA completion handler, and
by a timer to handle DMA time-out.

As there are always two receive DMA requests active, it's possible that
the receive DMA completion handler is called a second time before the
workqueue function runs.

As the time-out handler re-enables the receive interrupt, an interrupt
may come in before time-out has been fully handled.

Move part 1 into the receive DMA completion handler, and move part 2
into the receive DMA time-out handler, to fix these race conditions.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
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 7d8b2644e06d4b8c40b53066b14f60cdab09a28d..eb2b369b1cf1be0b1b837e6cbb2a980ae3f4510a 100644 (file)
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -115,7 +115,6 @@ struct sci_port {
        struct sh_dmae_slave            param_tx;
        struct sh_dmae_slave            param_rx;
        struct work_struct              work_tx;
-       struct work_struct              work_rx;
        struct timer_list               rx_timer;
        unsigned int                    rx_timeout;
 #endif
@@ -1106,6 +1105,7 @@ static void sci_dma_rx_complete(void *arg)
 {
        struct sci_port *s = arg;
        struct uart_port *port = &s->port;
+       struct dma_async_tx_descriptor *desc;
        unsigned long flags;
        int active, count = 0;
 
@@ -1120,12 +1120,32 @@ static void sci_dma_rx_complete(void *arg)
 
        mod_timer(&s->rx_timer, jiffies + s->rx_timeout);
 
-       spin_unlock_irqrestore(&port->lock, flags);
-
        if (count)
                tty_flip_buffer_push(&port->state->port);
 
-       schedule_work(&s->work_rx);
+       desc = dmaengine_prep_slave_sg(s->chan_rx, &s->sg_rx[active], 1,
+                                      DMA_DEV_TO_MEM,
+                                      DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+       if (!desc)
+               goto fail;
+
+       desc->callback = sci_dma_rx_complete;
+       desc->callback_param = s;
+       s->cookie_rx[active] = dmaengine_submit(desc);
+       if (dma_submit_error(s->cookie_rx[active]))
+               goto fail;
+
+       s->active_rx = s->cookie_rx[!active];
+
+       dev_dbg(port->dev, "%s: cookie %d #%d, new active cookie %d\n",
+               __func__, s->cookie_rx[active], active, s->active_rx);
+       spin_unlock_irqrestore(&port->lock, flags);
+       return;
+
+fail:
+       spin_unlock_irqrestore(&port->lock, flags);
+       dev_warn(port->dev, "Failed submitting Rx DMA descriptor\n");
+       sci_rx_dma_release(s, true);
 }
 
 static void sci_tx_dma_release(struct sci_port *s, bool enable_pio)
@@ -1186,72 +1206,6 @@ fail:
        sci_rx_dma_release(s, true);
 }
 
-static void work_fn_rx(struct work_struct *work)
-{
-       struct sci_port *s = container_of(work, struct sci_port, work_rx);
-       struct uart_port *port = &s->port;
-       struct dma_async_tx_descriptor *desc;
-       struct dma_tx_state state;
-       enum dma_status status;
-       unsigned long flags;
-       int new;
-
-       spin_lock_irqsave(&port->lock, flags);
-       new = sci_dma_rx_find_active(s);
-       if (new < 0) {
-               spin_unlock_irqrestore(&port->lock, flags);
-               return;
-       }
-
-       status = dmaengine_tx_status(s->chan_rx, s->active_rx, &state);
-       if (status != DMA_COMPLETE) {
-               /* Handle incomplete DMA receive */
-               struct dma_chan *chan = s->chan_rx;
-               unsigned int read;
-               int count;
-
-               dmaengine_terminate_all(chan);
-               read = sg_dma_len(&s->sg_rx[new]) - state.residue;
-               dev_dbg(port->dev, "Read %u bytes with cookie %d\n", read,
-                       s->active_rx);
-
-               if (read) {
-                       count = sci_dma_rx_push(s, s->rx_buf[new], read);
-                       if (count)
-                               tty_flip_buffer_push(&port->state->port);
-               }
-
-               spin_unlock_irqrestore(&port->lock, flags);
-
-               sci_submit_rx(s);
-               return;
-       }
-
-       desc = dmaengine_prep_slave_sg(s->chan_rx, &s->sg_rx[new], 1,
-                                      DMA_DEV_TO_MEM,
-                                      DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
-       if (!desc)
-               goto fail;
-
-       desc->callback = sci_dma_rx_complete;
-       desc->callback_param = s;
-       s->cookie_rx[new] = dmaengine_submit(desc);
-       if (dma_submit_error(s->cookie_rx[new]))
-               goto fail;
-
-       s->active_rx = s->cookie_rx[!new];
-
-       dev_dbg(port->dev, "%s: cookie %d #%d, new active cookie %d\n",
-               __func__, s->cookie_rx[new], new, s->active_rx);
-       spin_unlock_irqrestore(&port->lock, flags);
-       return;
-
-fail:
-       spin_unlock_irqrestore(&port->lock, flags);
-       dev_warn(port->dev, "Failed submitting Rx DMA descriptor\n");
-       sci_rx_dma_release(s, true);
-}
-
 static void work_fn_tx(struct work_struct *work)
 {
        struct sci_port *s = container_of(work, struct sci_port, work_tx);
@@ -1321,15 +1275,49 @@ static void rx_timer_fn(unsigned long arg)
 {
        struct sci_port *s = (struct sci_port *)arg;
        struct uart_port *port = &s->port;
-       u16 scr = serial_port_in(port, SCSCR);
+       struct dma_tx_state state;
+       enum dma_status status;
+       unsigned long flags;
+       unsigned int read;
+       int active, count;
+       u16 scr;
+
+       spin_lock_irqsave(&port->lock, flags);
 
+       dev_dbg(port->dev, "DMA Rx timed out\n");
+       scr = serial_port_in(port, SCSCR);
        if (port->type == PORT_SCIFA || port->type == PORT_SCIFB) {
                scr &= ~SCSCR_RDRQE;
                enable_irq(s->irqs[SCIx_RXI_IRQ]);
        }
        serial_port_out(port, SCSCR, scr | SCSCR_RIE);
-       dev_dbg(port->dev, "DMA Rx timed out\n");
-       schedule_work(&s->work_rx);
+
+       active = sci_dma_rx_find_active(s);
+       if (active < 0) {
+               spin_unlock_irqrestore(&port->lock, flags);
+               return;
+       }
+
+       status = dmaengine_tx_status(s->chan_rx, s->active_rx, &state);
+       if (status == DMA_COMPLETE)
+               dev_dbg(port->dev, "Cookie %d #%d has already completed\n",
+                       s->active_rx, active);
+
+       /* Handle incomplete DMA receive */
+       dmaengine_terminate_all(s->chan_rx);
+       read = sg_dma_len(&s->sg_rx[active]) - state.residue;
+       dev_dbg(port->dev, "Read %u bytes with cookie %d\n", read,
+               s->active_rx);
+
+       if (read) {
+               count = sci_dma_rx_push(s, s->rx_buf[active], read);
+               if (count)
+                       tty_flip_buffer_push(&port->state->port);
+       }
+
+       spin_unlock_irqrestore(&port->lock, flags);
+
+       sci_submit_rx(s);
 }
 
 static void sci_request_dma(struct uart_port *port)
@@ -1413,7 +1401,6 @@ static void sci_request_dma(struct uart_port *port)
                        dma += s->buf_len_rx;
                }
 
-               INIT_WORK(&s->work_rx, work_fn_rx);
                setup_timer(&s->rx_timer, rx_timer_fn, (unsigned long)s);
 
                sci_submit_rx(s);