RE: [PATCH v4 3/5] tty: serial: sh-sci: Fix Tx on SCI IP

From: Biju Das <biju.das.jz@bp.renesas.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	"linux-serial@vger.kernel.org" <linux-serial@vger.kernel.org>,
	Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>,
	"linux-renesas-soc@vger.kernel.org" 
	<linux-renesas-soc@vger.kernel.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: RE: [PATCH v4 3/5] tty: serial: sh-sci: Fix Tx on SCI IP
Date: Thu, 6 Apr 2023 06:50:46 +0000	[thread overview]
Message-ID: <OS0PR01MB59220B26E3627CF3EFC94D5E86919@OS0PR01MB5922.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <20230321114753.75038-4-biju.das.jz@bp.renesas.com>

Hi All,

I split this patch into 2([1] & [2]) after fixing commit message
and merged with the series[3] to avoid any dependencies.

[1] https://lore.kernel.org/linux-renesas-soc/20230331113346.170602-4-biju.das.jz@bp.renesas.com/T/#u
[2] https://lore.kernel.org/linux-renesas-soc/20230331113346.170602-4-biju.das.jz@bp.renesas.com/T/#md8ae156345aed10bdeba764dcf2253f00b02e38c

[3] https://lore.kernel.org/linux-renesas-soc/20230331113346.170602-4-biju.das.jz@bp.renesas.com/T/#me7f60560fbf24bf361d70ccb6ba223e92a60de9b

Cheers,
Biju

> Subject: [PATCH v4 3/5] tty: serial: sh-sci: Fix Tx on SCI IP
> 
> For SCI, the TE (transmit enable) must be set after setting TIE (transmit
> interrupt enable) or in the same instruction to start the transmission.
> Set TE bit in sci_start_tx() instead of set_termios() for SCI and clear TE
> bit, if circular buffer is empty in sci_transmit_chars().
> 
> Fixes: 93bcefd4c6ba ("serial: sh-sci: Fix setting SCSCR_TIE while
> transferring data")
> Cc: stable@vger.kernel.org
> Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
> ---
> v3->v4:
>  * Updated fixes tag.
> v3:
>  * New patch
> ---
>  drivers/tty/serial/sh-sci.c | 25 +++++++++++++++++++++++--
>  1 file changed, 23 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index
> 15954ca3e9dc..bcc4152ce043 100644
> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
> @@ -596,6 +596,15 @@ static void sci_start_tx(struct uart_port *port)
>  	if (!s->chan_tx || port->type == PORT_SCIFA || port->type ==
> PORT_SCIFB) {
>  		/* Set TIE (Transmit Interrupt Enable) bit in SCSCR */
>  		ctrl = serial_port_in(port, SCSCR);
> +
> +		/*
> +		 * For SCI, TE (transmit enable) must be set after setting TIE
> +		 * (transmit interrupt enable) or in the same instruction to
> start
> +		 * the transmit process.
> +		 */
> +		if (port->type == PORT_SCI)
> +			ctrl |= SCSCR_TE;
> +
>  		serial_port_out(port, SCSCR, ctrl | SCSCR_TIE);
>  	}
>  }
> @@ -834,6 +843,12 @@ static void sci_transmit_chars(struct uart_port *port)
>  			c = xmit->buf[xmit->tail];
>  			xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
>  		} else {
> +			if (port->type == PORT_SCI) {
> +				ctrl = serial_port_in(port, SCSCR);
> +				ctrl &= ~SCSCR_TE;
> +				serial_port_out(port, SCSCR, ctrl);
> +				return;
> +			}
>  			break;
>  		}
> 
> @@ -2580,8 +2595,14 @@ static void sci_set_termios(struct uart_port *port,
> struct ktermios *termios,
>  		sci_set_mctrl(port, port->mctrl);
>  	}
> 
> -	scr_val |= SCSCR_RE | SCSCR_TE |
> -		   (s->cfg->scscr & ~(SCSCR_CKE1 | SCSCR_CKE0));
> +	/*
> +	 * For SCI, TE (transmit enable) must be set after setting TIE
> +	 * (transmit interrupt enable) or in the same instruction to
> +	 * start the transmitting process. So skip setting TE here for SCI.
> +	 */
> +	if (port->type != PORT_SCI)
> +		scr_val |= SCSCR_TE;
> +	scr_val |= SCSCR_RE | (s->cfg->scscr & ~(SCSCR_CKE1 | SCSCR_CKE0));
>  	serial_port_out(port, SCSCR, scr_val | s->hscif_tot);
>  	if ((srr + 1 == 5) &&
>  	    (port->type == PORT_SCIFA || port->type == PORT_SCIFB)) {
> --
> 2.25.1