RE: [PATCH v3 3/5] tty: serial: sh-sci: Fix TE setting on SCI IP

[Biju Das <biju.das.jz@bp.renesas.com>]

Hi All,

> -----Original Message-----
> From: Biju Das <biju.das.jz@bp.renesas.com>
> Sent: Friday, March 31, 2023 12:34 PM
> To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Biju Das <biju.das.jz@bp.renesas.com>; Jiri Slaby
> <jirislaby@kernel.org>; Geert Uytterhoeven <geert+renesas@glider.be>;
> Yoshinori Sato <ysato@users.sourceforge.jp>; linux-serial@vger.kernel.org;
> Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>; linux-
> renesas-soc@vger.kernel.org; stable@vger.kernel.org
> Subject: [PATCH v3 3/5] tty: serial: sh-sci: Fix TE setting on SCI IP
> 
> As per the RZ/G2L users hardware manual (Rev.1.20 Sep, 2022), section
> 23.3.7 Serial Data Transmission (Asynchronous Mode) it is mentioned that the
> TE (transmit enable) must be set after setting TIE (transmit interrupt
> enable) or these 2 bits are set to 1 simultaneously by a single instruction.
> So set these 2 bits in single instruction.
> 
> Fixes: 93bcefd4c6ba ("serial: sh-sci: Fix setting SCSCR_TIE while
> transferring data")
> Cc: stable@vger.kernel.org

I rechecked and the fixes tag is wrong. So, I would like to remove fixes
tag for this patch in next version.

Cheers,
Biju

> Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
> ---
> v3:
>  * New patch moved here from Renesas SCI fixes patch series
>  * Updated commit description
>  * Moved handling of clearing TE bit as separate patch#5.
> ---
>  drivers/tty/serial/sh-sci.c | 19 +++++++++++++++++--
>  1 file changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index
> 15743c2f3d3d..32f5c1f7d697 100644
> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
> @@ -601,6 +601,15 @@ static void sci_start_tx(struct uart_port *port)
>  	    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);
>  	}
>  }
> @@ -2600,8 +2609,14 @@ 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