Commit 67f462b0 authored by Geert Uytterhoeven's avatar Geert Uytterhoeven Committed by Greg Kroah-Hartman
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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: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e1910fcd

drivers/tty/serial/sh-sci.c

+61 −74
Original line number Diff line number Diff line
@@ -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 @@ static void sci_submit_rx(struct sci_port *s) 
	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);