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Commit 0e31c8d1 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Greg Kroah-Hartman
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tty: serial: 8250_omap: add custom DMA-RX callback 



The omap needs a DMA request pending right away. If it is
enqueued once the bytes are in the FIFO then nothing will happen
and the FIFO will be later purged via RX-timeout interrupt.
This patch enqueues RX-DMA request on completion but not if it
was aborted on error. The first enqueue will happen in the driver
in startup.

Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 31a17132

drivers/tty/serial/8250/8250_omap.c

+96 −0
Original line number Diff line number Diff line
@@ -619,6 +619,102 @@ static void omap_8250_unthrottle(struct uart_port *port) 
}



#ifdef CONFIG_SERIAL_8250_DMA

static int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir);



static void __dma_rx_do_complete(struct uart_8250_port *p, bool error)

{

	struct uart_8250_dma    *dma = p->dma;

	struct tty_port         *tty_port = &p->port.state->port;

	struct dma_tx_state     state;

	int                     count;



	dma_sync_single_for_cpu(dma->rxchan->device->dev, dma->rx_addr,

				dma->rx_size, DMA_FROM_DEVICE);



	dma->rx_running = 0;

	dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);

	dmaengine_terminate_all(dma->rxchan);



	count = dma->rx_size - state.residue;



	tty_insert_flip_string(tty_port, dma->rx_buf, count);

	p->port.icount.rx += count;

	if (!error)

		omap_8250_rx_dma(p, 0);



	tty_flip_buffer_push(tty_port);

}



static void __dma_rx_complete(void *param)

{

	__dma_rx_do_complete(param, false);

}



static int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir)

{

	struct uart_8250_dma            *dma = p->dma;

	struct dma_async_tx_descriptor  *desc;



	switch (iir & 0x3f) {

	case UART_IIR_RLSI:

		/* 8250_core handles errors and break interrupts */

		if (dma->rx_running) {

			dmaengine_pause(dma->rxchan);

			__dma_rx_do_complete(p, true);

		}

		return -EIO;

	case UART_IIR_RX_TIMEOUT:

		/*

		 * If RCVR FIFO trigger level was not reached, complete the

		 * transfer and let 8250_core copy the remaining data.

		 */

		if (dma->rx_running) {

			dmaengine_pause(dma->rxchan);

			__dma_rx_do_complete(p, true);

		}

		return -ETIMEDOUT;

	case UART_IIR_RDI:

		/*

		 * The OMAP UART is a special BEAST. If we receive RDI we _have_

		 * a DMA transfer programmed but it didn't work. One reason is

		 * that we were too slow and there were too many bytes in the

		 * FIFO, the UART counted wrong and never kicked the DMA engine

		 * to do anything. That means once we receive RDI on OMAP then

		 * the DMA won't do anything soon so we have to cancel the DMA

		 * transfer and purge the FIFO manually.

		 */

		if (dma->rx_running) {

			dmaengine_pause(dma->rxchan);

			__dma_rx_do_complete(p, true);

		}

		return -ETIMEDOUT;



	default:

		break;

	}



	if (dma->rx_running)

		return 0;



	desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,

					   dma->rx_size, DMA_DEV_TO_MEM,

					   DMA_PREP_INTERRUPT | DMA_CTRL_ACK);

	if (!desc)

		return -EBUSY;



	dma->rx_running = 1;

	desc->callback = __dma_rx_complete;

	desc->callback_param = p;



	dma->rx_cookie = dmaengine_submit(desc);



	dma_sync_single_for_device(dma->rxchan->device->dev, dma->rx_addr,

				   dma->rx_size, DMA_FROM_DEVICE);



	dma_async_issue_pending(dma->rxchan);

	return 0;

}



static int omap_8250_tx_dma(struct uart_8250_port *p);



static void omap_8250_dma_tx_complete(void *param)