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@xxxxxxxxx>
---
v4:
- Dropped RFC status,
- Rebased on top of "[PATCH] serial: sh-sci: Shuffle functions
around", hence it's no longer needed to move sci_rx_dma_release()
up,
v3:
- New.
---
drivers/tty/serial/sh-sci.c | 135 ++++++++++++++++++++------------------------
1 file changed, 61 insertions(+), 74 deletions(-)
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 7d8b2644e06d4b8c..eb2b369b1cf1be0b 100644
--- 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);
--
1.9.1
--
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