RE: [PATCH v2] serial: sh-sci: Stop dmaengine transfer in sci_stop_tx()

[Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>]

Hi Jiri,

Thank you for your review!

> From: Jiri Slaby, Sent: Friday, June 4, 2021 7:22 PM
> 
> On 04. 06. 21, 11:57, Yoshihiro Shimoda wrote:
> > 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
> >
> > Notes:
> >   - sci_dma_stop_tx() is a macro in the .h file because struct sci_port
> >     is declared in the .c file and #ifdef should be in the .h file.
> >   - This patch uses dmaengine_terminate_async() so that we can apply
> >     this 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>
> > ---
<snip>
> > diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
> > index 4baf1316ea72..3793cf9f352c 100644
> > --- a/drivers/tty/serial/sh-sci.c
> > +++ b/drivers/tty/serial/sh-sci.c
> > @@ -610,6 +610,8 @@ static void sci_stop_tx(struct uart_port *port)
> >   	ctrl &= ~SCSCR_TIE;
> >
> >   	serial_port_out(port, SCSCR, ctrl);
> > +
> > +	sci_dma_stop_tx(port);
> >   }
> >
> >   static void sci_start_rx(struct uart_port *port)
> > diff --git a/drivers/tty/serial/sh-sci.h b/drivers/tty/serial/sh-sci.h
> > index c0dfe4382898..435c674af1ce 100644
> > --- a/drivers/tty/serial/sh-sci.h
> > +++ b/drivers/tty/serial/sh-sci.h
> > @@ -174,3 +174,19 @@ enum {
> >   	(((port)->type == PORT_SCI) ? SCI_TDxE_CLEAR : SCIF_TDxE_CLEAR)
> >   #define SCxSR_BREAK_CLEAR(port) \
> >   	(((port)->type == PORT_SCI) ? SCI_BREAK_CLEAR : SCIF_BREAK_CLEAR)
> > +
> > +#ifdef CONFIG_SERIAL_SH_SCI_DMA
> > +#define sci_dma_stop_tx(port)					\
> 
> Ouch. First, why this needs to be in a header?

The v1 patch [1] putted #ifdef in .c file, so that I got feedback from Greg like below:
"Please do not put #ifdef in .c files, this should be possible without that."

[1]
https://lore.kernel.org/linux-renesas-soc/TY2PR01MB3692C545672195370487FA60D83C9@TY2PR01MB3692.jpnprd01.prod.outlook.com/T/#md5b58540e26a28ef1acddfc326c62bfde73e8e8a

> Second, please don't do this by a macro.

I got it. I'll try to fix this issue somehow...

Best regards,
Yoshihiro Shimoda