linux-kernel - Re: [PATCH v2 1/5] serial: 8250: extract serial8250_init

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Message-ID: <4d6b65af-294c-fd02-af91-099e22420472@linux.intel.com>
Date: Tue, 24 Jun 2025 14:15:27 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
    linux-serial <linux-serial@...r.kernel.org>, 
    LKML <linux-kernel@...r.kernel.org>, 
    Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH v2 1/5] serial: 8250: extract serial8250_init_mctrl()

On Tue, 24 Jun 2025, Ilpo Järvinen wrote:

> On Tue, 24 Jun 2025, Jiri Slaby (SUSE) wrote:
> 
> > After commit 795158691cc0 ("serial: 8250: extract
> > serial8250_initialize()"), split serial8250_initialize() even more --
> > the mctrl part of this code can be separated into
> > serial8250_init_mctrl() -- done now.
> > 
> > Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
> > Suggested-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> 
> Heh, I didn't even realize I was suggesting this :-D but it's good 
> nonetheless.
> 
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> 
> > Cc: Andy Shevchenko <andy.shevchenko@...il.com>
> > ---
> > [v2]
> > * use port-> directly.
> > * do not remove curly braces.
> > Both rebase errors -- noticed by Andy.
> > ---
> >  drivers/tty/serial/8250/8250_port.c | 21 +++++++++++++--------
> >  1 file changed, 13 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> > index 48c30e158cb8..0f85a2f292fc 100644
> > --- a/drivers/tty/serial/8250/8250_port.c
> > +++ b/drivers/tty/serial/8250/8250_port.c
> > @@ -2216,15 +2216,8 @@ static void serial8250_THRE_test(struct uart_port *port)
> >  		up->bugs |= UART_BUG_THRE;
> >  }
> >  
> > -static void serial8250_initialize(struct uart_port *port)
> > +static void serial8250_init_mctrl(struct uart_port *port)
> >  {
> > -	struct uart_8250_port *up = up_to_u8250p(port);
> > -	unsigned long flags;
> > -	bool lsr_TEMT, iir_NOINT;
> > -
> > -	serial_port_out(port, UART_LCR, UART_LCR_WLEN8);
> > -
> > -	uart_port_lock_irqsave(port, &flags);
> >  	if (port->flags & UPF_FOURPORT) {

I should have also added what I meant with my earlier suggestion. AFAICT, 
this UPF_FOURPORT thing can only occur if SERIAL_8250_FOURPORT is enabled.

The challenge obviously are the if/else constructs but there are a few 
places that do port->flags & UPF_FOURPORT specific thing and something 
else otherwise. That hw-specific code could be placed into the hw-specific 
8250_fourport.c file if the hw-specific function is made to return true 
if it did match, and the generic code runs otherwise.

I also have no idea why serial/sunsu.c checks UPF_FOURPORT, perhaps that's 
copy-paste in action. :-)

> >  		if (!port->irq)
> >  			port->mctrl |= TIOCM_OUT1;
> > @@ -2235,6 +2228,18 @@ static void serial8250_initialize(struct uart_port *port)
> >  	}
> >  
> >  	serial8250_set_mctrl(port, port->mctrl);
> > +}
> > +
> > +static void serial8250_initialize(struct uart_port *port)
> > +{
> > +	struct uart_8250_port *up = up_to_u8250p(port);
> > +	unsigned long flags;
> > +	bool lsr_TEMT, iir_NOINT;
> > +
> > +	serial_port_out(port, UART_LCR, UART_LCR_WLEN8);
> > +
> > +	uart_port_lock_irqsave(port, &flags);
> > +	serial8250_init_mctrl(port);
> >  
> >  	/*
> >  	 * Serial over Lan (SoL) hack:
> > 
> 
> 

-- 
 i.