Commit 0fcb7901 authored Sep 29, 2014 by Sebastian Andrzej Siewior Committed by Greg Kroah-Hartman Nov 05, 2014

tty: serial: 8250_dma: keep own book keeping about RX transfers



After dmaengine_terminate_all() has been invoked then both DMA drivers
(edma and omap-dma) do not invoke dma_cookie_complete() to mark the
transfer as complete. This dma_cookie_complete() is performed by the
Synopsys DesignWare driver which is probably the only one that is used
by omap8250-dma and hence don't see following problem…
…which is that once a RX transfer has been terminated then following
query of channel status reports DMA_IN_PROGRESS (again: the actual
transfer has been canceled, there is nothing going on anymore).

This means that serial8250_rx_dma() never enqueues another DMA transfer
because it (wrongly) assumes that there is a transer already pending.

Vinod Koul refuses to accept a patch which adds this
dma_cookie_complete() to both drivers and so dmaengine_tx_status() would
report DMA_COMPLETE instead (and behave like the Synopsys DesignWare
driver already does). He argues that I am not allowed to use the cookie
to query the status and that the driver already cleaned everything up after
the invokation of dmaengine_terminate_all().

To end this I add a bookkeeping whether or not a RX-transfer has been
started to the 8250-dma code. It has already been done for the TX side.
*Now* we learn about the RX status based on our bookkeeping and don't
need dmaengine_tx_status() for this anymore.

Cc: vinod.koul@intel.com
Reviewed-by: Tony Lindgren <tony@atomide.com>
Tested-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent b2202821

drivers/tty/serial/8250/8250.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -42,6 +42,7 @@ struct uart_8250_dma {

		unsigned char tx_running:1;
		unsigned char tx_err: 1;
		unsigned char rx_running:1;
		};

		struct old_serial_port {

drivers/tty/serial/8250/8250_dma.c

+4 −6

Original line number	Diff line number	Diff line
		@@ -61,6 +61,7 @@ static void __dma_rx_complete(void *param)
		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);

		@@ -123,10 +124,6 @@ int serial8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
		{
		struct uart_8250_dma *dma = p->dma;
		struct dma_async_tx_descriptor *desc;
		struct dma_tx_state state;
		int dma_status;

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

		switch (iir & 0x3f) {
		case UART_IIR_RLSI:
		@@ -137,7 +134,7 @@ int serial8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
		* If RCVR FIFO trigger level was not reached, complete the
		* transfer and let 8250_core copy the remaining data.
		*/
		if (dma_status == DMA_IN_PROGRESS) {
		if (dma->rx_running) {
		dmaengine_pause(dma->rxchan);
		__dma_rx_complete(p);
		}
		@@ -146,7 +143,7 @@ int serial8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
		break;
		}

		if (dma_status)
		if (dma->rx_running)
		return 0;

		desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
		@@ -155,6 +152,7 @@ int serial8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
		if (!desc)
		return -EBUSY;

		dma->rx_running = 1;
		desc->callback = __dma_rx_complete;
		desc->callback_param = p;