linux-kernel - Re: [PATCH] tty: serial: 8250: exar: fix kernel warning in default

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Message-ID: <aJJ49CSBqGZM_b1Y@smile.fi.intel.com>
Date: Wed, 6 Aug 2025 00:34:44 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Wilken Gottwalt <wilken.gottwalt@...teo.net>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	Jiri Slaby <jirislaby@...nel.org>,
	Parker Newman <pnewman@...necttech.com>
Subject: Re: [PATCH] tty: serial: 8250: exar: fix kernel warning in
 default_setup function

On Wed, Jul 30, 2025 at 11:03:50AM +0000, Wilken Gottwalt wrote:
> On Tue, 29 Jul 2025 10:48:17 +0200
> Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:
> 
> > > diff --git a/drivers/tty/serial/8250/8250_exar.c b/drivers/tty/serial/8250/8250_exar.c
> > > index 04a0cbab02c2..5660bb897803 100644
> > > --- a/drivers/tty/serial/8250/8250_exar.c
> > > +++ b/drivers/tty/serial/8250/8250_exar.c
> > > @@ -500,12 +500,13 @@ static int default_setup(struct exar8250 *priv, struct pci_dev *pcidev,
> > >  			 struct uart_8250_port *port)
> > >  {
> > >  	const struct exar8250_board *board = priv->board;
> > > +	unsigned int bar = 0;
> > >  	unsigned char status;
> > > -	int err;
> > >  
> > > -	err = serial8250_pci_setup_port(pcidev, port, 0, offset, board->reg_shift);
> > > -	if (err)
> > > -		return err;
> > > +	port->port.iotype = UPIO_MEM;
> > > +	port->port.mapbase = pci_resource_start(pcidev, bar) + offset;
> > > +	port->port.membase = priv->virt + offset;
> > > +	port->port.regshift = board->reg_shift;
> > 
> > And so now serial8250_pci_setup_port() is never called?  Are you sure
> > that's ok?
> 
> Hi Greg,
> 
> I will not provide a second version of this patch, because this is a bigger
> problem involving 8250_exar, 8250_pci and 8250_pci1xxxx. With the changes from
> kernel 6.10 to 6.11 the underlying pcim_* functions where changed. The
> serial8250_pci_setup_port() does checks on pci_dev + BAR where resources were
> already mapped via pcim_iomap(), pci_iomap() or even pci_ioremap_bar(). Not
> sure if mixing this is a good idea after the kernel 6.11 changes.
> 
> serial8250_pci_setup_port() uses pcim_iomap() and pcim_iomap_table() for checking
> these already mapped resources. But the pcim_iomap_table() is deprecated and
> suggests to use pcim_iomap() function to aquire the pointer to the resources
> while at the same time pcim_iomap() description states, don't use this function 
> twice on the same BAR. I think the most sane approach would be to drop the
> pcim_iomap() and pcim_iomap_table() checks from the serial8250_pci_setup_port()
> function. But I can not fully test this, I only have access to some hardware
> used by the 8250_exar driver. I also CC Andy and Parker, both worked on the
> affected code.

I'm on vacations right now and I lost context of this a long ago, please Cc me
to any new version of this change to have a fresh look.

-- 
With Best Regards,
Andy Shevchenko