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

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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>
This commit is contained in:
Sebastian Andrzej Siewior 2014-09-29 20:06:41 +02:00 committed by Greg Kroah-Hartman
parent b220282156
commit 0fcb7901f9
2 changed files with 5 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
drivers/tty/serial/8250/8250.h
View File

@ -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 {

10
drivers/tty/serial/8250/8250_dma.c
View File

@ -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;