[linux-yocto] [PATCH 04/15] serial: 8250_dma: power off device after TX is done

[Nilesh Bacchewar]

From: Andy Shevchenko <andriy.shevchenko at linux.intel.com>

Backport:
 - Upstream-Status: Pending.
 [https://bitbucket.org/andy-shev/linux/commits/5fe86674840c6773d09943a78a5f7f3bf2420ffd?at=master]

When any 8250 based driver sets up DMA and has UART_CAP_RPM capability enabled
the device is left powered on after transfer is done. We need to schedule a
device suspend operation when DMA completes the transfer.

The patch is based on the work done by the reporter.

Reported-by: Huiquan Zhong <huiquan.zhong at intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
---
 drivers/tty/serial/8250/8250_dma.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
index 78259d3..d9b93d1 100644
--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -72,10 +72,15 @@ int serial8250_tx_dma(struct uart_8250_port *p)
 	struct dma_async_tx_descriptor	*desc;
 	int ret;
 
-	if (uart_tx_stopped(&p->port) || dma->tx_running ||
-	    uart_circ_empty(xmit))
+	if (dma->tx_running)
 		return 0;
 
+	if (uart_tx_stopped(&p->port) || uart_circ_empty(xmit)) {
+		/* We have been called from __dma_tx_complete() */
+		serial8250_rpm_put_tx(p);
+		return 0;
+	}
+
 	dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
 
 	desc = dmaengine_prep_slave_single(dma->txchan,
-- 
1.9.1