From: Geert Uytterhoeven Date: Fri, 18 Sep 2015 11:08:25 +0000 (+0200) Subject: serial: sh-sci: Get rid of the workqueue to handle receive DMA requests X-Git-Tag: firefly_0821_release~176^2~803^2~104 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=67f462b069e9d2087d3fe838584730ecefcf9c66;p=firefly-linux-kernel-4.4.55.git 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 Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index 7d8b2644e06d..eb2b369b1cf1 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);