Hi Geert-san, Sergei-san,

From: Geert Uytterhoeven, Sent: Thursday, June 10, 2021 12:30 AM
On Wed, Jun 9, 2021 at 5:09 PM Sergei Shtylyov
[off-list ref] wrote:

quoted

On 6/9/21 4:49 AM, Yoshihiro Shimoda wrote:

quoted

Stop dmaengine transfer in sci_stop_tx(). Otherwise, the following
message is possible output when system enters suspend and while
transferring data, because clearing TIE bit in SCSCR is not able to
stop any dmaengine transfer.

    sh-sci e6550000.serial: ttySC1: Unable to drain transmitter

Note that this patch uses dmaengine_terminate_async() so that
we can apply this patch into longterm kernel v4.9.x or later.

Fixes: 73a19e4c0301 ("serial: sh-sci: Add DMA support.")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
---

 drivers/tty/serial/sh-sci.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 4baf1316ea72..2d5487bf6855 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c

@@ -610,6 +610,14 @@ static void sci_stop_tx(struct uart_port *port)
      ctrl &= ~SCSCR_TIE;

      serial_port_out(port, SCSCR, ctrl);
+
+#ifdef CONFIG_SERIAL_SH_SCI_DMA

   Why not use IS_ENABLED() instead? Gets rid of #ifdef. :-)

quoted

+     if (to_sci_port(port)->chan_tx &&
+         !dma_submit_error(to_sci_port(port)->cookie_tx)) {
+             dmaengine_terminate_async(to_sci_port(port)->chan_tx);
+             to_sci_port(port)->cookie_tx = -EINVAL;

Because chan_tx and cookie_tx do not exist if CONFIG_SERIAL_SH_SCI_DMA
is disabled.

This is a nit though, chan_tx always exists.

Yes, that's why all the DMA code in this driver (.c file) is protected by
#ifdef CONFIG_SERIAL_SH_SCI_DMA.

I'm thinking we have to remove #ifdef from sh-sci.c file at first...

Best regards,
Yoshihiro Shimoda