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Subject: Re: [PATCH] serial: amba-pl011: add RS485 support
To:     Jiri Slaby <jirislaby@kernel.org>, gregkh@linuxfoundation.org
Cc:     linux@armlinux.org.uk, linux-serial@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20210610135004.7585-1-LinoSanfilippo@gmx.de>
 <5f00ff43-9287-4027-7d80-474da957703c@kernel.org>
From:   Lino Sanfilippo <LinoSanfilippo@gmx.de>
Message-ID: <98c29d64-3155-4769-8336-413325de4057@gmx.de>
Date:   Thu, 17 Jun 2021 18:12:00 +0200
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Hi,

On 16.06.21 at 08:18, Jiri Slaby wrote:

>> +=A0=A0=A0 if (port->rs485.delay_rts_before_send)
>> +=A0=A0=A0=A0=A0=A0=A0 mdelay(port->rs485.delay_rts_before_send);
>
> This is up to 1 second delay with interrupts disabled. Definitely not ni=
ce. 8250 clamps this to 100 ms at least, why did you choose 1000 ms?
>

I got this value from rs485.yaml where the max number for both rts delay b=
efore and after send
is specified as 1000ms. I thought to keep it up to the user to choose a sa=
ne setting. But yes,
its a very long time with interrupts disabled. I will send an updated vers=
ion of this patch that
limits both values to 100ms.


os(struct uart_port *port, struct ktermios *termios,
>> =A0=A0=A0=A0=A0 unsigned int lcr_h, old_cr;
>> =A0=A0=A0=A0=A0 unsigned long flags;
>> =A0=A0=A0=A0=A0 unsigned int baud, quot, clkdiv;
>> +=A0=A0=A0 unsigned int bits;
>> =A0 =A0=A0=A0=A0=A0 if (uap->vendor->oversampling)
>> =A0=A0=A0=A0=A0=A0=A0=A0=A0 clkdiv =3D 8;
>> @@ -1968,25 +2049,32 @@ pl011_set_termios(struct uart_port *port, struc=
t ktermios *termios,
>> =A0=A0=A0=A0=A0 switch (termios->c_cflag & CSIZE) {
>> =A0=A0=A0=A0=A0 case CS5:
>> =A0=A0=A0=A0=A0=A0=A0=A0=A0 lcr_h =3D UART01x_LCRH_WLEN_5;
>> +=A0=A0=A0=A0=A0=A0=A0 bits =3D 7;
>> =A0=A0=A0=A0=A0=A0=A0=A0=A0 break;
>> =A0=A0=A0=A0=A0 case CS6:
>> =A0=A0=A0=A0=A0=A0=A0=A0=A0 lcr_h =3D UART01x_LCRH_WLEN_6;
>> +=A0=A0=A0=A0=A0=A0=A0 bits =3D 8;
>> =A0=A0=A0=A0=A0=A0=A0=A0=A0 break;
>> =A0=A0=A0=A0=A0 case CS7:
>> =A0=A0=A0=A0=A0=A0=A0=A0=A0 lcr_h =3D UART01x_LCRH_WLEN_7;
>> +=A0=A0=A0=A0=A0=A0=A0 bits =3D 9;
>> =A0=A0=A0=A0=A0=A0=A0=A0=A0 break;
>> =A0=A0=A0=A0=A0 default: // CS8
>> =A0=A0=A0=A0=A0=A0=A0=A0=A0 lcr_h =3D UART01x_LCRH_WLEN_8;
>> +=A0=A0=A0=A0=A0=A0=A0 bits =3D 10;
>> =A0=A0=A0=A0=A0=A0=A0=A0=A0 break;
>> =A0=A0=A0=A0=A0 }
>> -=A0=A0=A0 if (termios->c_cflag & CSTOPB)
>> +=A0=A0=A0 if (termios->c_cflag & CSTOPB) {
>> =A0=A0=A0=A0=A0=A0=A0=A0=A0 lcr_h |=3D UART01x_LCRH_STP2;
>> +=A0=A0=A0=A0=A0=A0=A0 bits++;
>> +=A0=A0=A0 }
>> =A0=A0=A0=A0=A0 if (termios->c_cflag & PARENB) {
>> =A0=A0=A0=A0=A0=A0=A0=A0=A0 lcr_h |=3D UART01x_LCRH_PEN;
>> =A0=A0=A0=A0=A0=A0=A0=A0=A0 if (!(termios->c_cflag & PARODD))
>> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 lcr_h |=3D UART01x_LCRH_EPS;
>> =A0=A0=A0=A0=A0=A0=A0=A0=A0 if (termios->c_cflag & CMSPAR)
>> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 lcr_h |=3D UART011_LCRH_SPS;
>> +=A0=A0=A0=A0=A0=A0=A0 bits++;
>> =A0=A0=A0=A0=A0 }
>
> You can do simply:
> =A0 bits =3D tty_get_frame_size(termios->c_cflag);
> now:
> https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git/commit/?h=
=3Dtty-testing&id=3D3ec2ff37230e1c961d4b0d0118dd23c46b5bcdbb

Ah thats a nice function, thanks for pointing at it. I will adjust the cod=
e accordingly.


>
> thanks,

Thanks for the review!

Regards,
Lino