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Date:   Fri, 4 Jun 2021 13:38:10 +0200
From:   "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
To:     Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Cc:     Jiri Slaby <jirislaby@kernel.org>,
        "linux-serial@vger.kernel.org" <linux-serial@vger.kernel.org>,
        "linux-renesas-soc@vger.kernel.org" 
        <linux-renesas-soc@vger.kernel.org>
Subject: Re: [PATCH v2] serial: sh-sci: Stop dmaengine transfer in
 sci_stop_tx()
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References: <20210604095704.756190-1-yoshihiro.shimoda.uh@renesas.com>
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On Fri, Jun 04, 2021 at 10:28:19AM +0000, Yoshihiro Shimoda wrote:
> 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."

Yes, but that does not mean using a macro, please do this correctly.

thanks,

greg k-h