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: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
drivers/tty/serial/8250/8250_omap.c | 96 +++++++++++++++++++++++++++++++++++++
1 file changed, 96 insertions(+)
diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index 5f183d197dfa..1659858e595a 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -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)
--
2.1.0
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