From: Muhammad Hamza Farooq Date: Fri, 18 Sep 2015 11:08:32 +0000 (+0200) Subject: serial: sh-sci: Pause DMA engine and get DMA status again X-Git-Tag: firefly_0821_release~176^2~803^2~97 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=e7327c09def48ccfd204025726f11b57a19a9c24;p=firefly-linux-kernel-4.4.55.git serial: sh-sci: Pause DMA engine and get DMA status again Occasionally, DMA transaction completes _after_ DMA engine is stopped. Verify if the transaction has not finished before forcing the engine to stop and push the data Signed-off-by: Muhammad Hamza Farooq 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 9406fe227bc7..b1d1ce1986e6 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -1277,6 +1277,7 @@ static bool filter(struct dma_chan *chan, void *slave) static void rx_timer_fn(unsigned long arg) { struct sci_port *s = (struct sci_port *)arg; + struct dma_chan *chan = s->chan_rx; struct uart_port *port = &s->port; struct dma_tx_state state; enum dma_status status; @@ -1305,6 +1306,21 @@ static void rx_timer_fn(unsigned long arg) return; } + dmaengine_pause(chan); + + /* + * sometimes DMA transfer doesn't stop even if it is stopped and + * data keeps on coming until transaction is complete so check + * for DMA_COMPLETE again + * Let packet complete handler take care of the packet + */ + status = dmaengine_tx_status(s->chan_rx, s->active_rx, &state); + if (status == DMA_COMPLETE) { + spin_unlock_irqrestore(&port->lock, flags); + dev_dbg(port->dev, "Transaction complete after DMA engine was stopped"); + return; + } + /* Handle incomplete DMA receive */ dmaengine_terminate_all(s->chan_rx); read = sg_dma_len(&s->sg_rx[active]) - state.residue;