Re: [PATCH] ns1650: refactor interrupt handling in ns16550_uart_dt_init()

[Julien Grall <julien@xxxxxxx>]

Hi,

On 13/07/2023 12:55, Oleksii wrote:
> On Thu, 2023-07-13 at 11:13 +0100, Julien Grall wrote:
> > Hi Jan,
> >
> > On 13/07/2023 11:08, Jan Beulich wrote:
> > > On 13.07.2023 11:30, Oleksii Kurochko wrote:
> > > > --- a/xen/drivers/char/ns16550.c
> > > > +++ b/xen/drivers/char/ns16550.c
> > > > @@ -1791,8 +1791,16 @@ static int __init
> > > > ns16550_uart_dt_init(struct dt_device_node *dev,
> > > >        }
> > > >    
> > > >        res = platform_get_irq(dev, 0);
> > > > -    if ( ! res )
> > > > -        return -EINVAL;
> > > > +    if ( res == -1 )
> > > > +    {
> > > > +        printk("ns1650: polling will be used\n");
> > > Nit: Please don't omit one of the two 5-s here.
> > >
> > > > +        /*
> > > > +         * There is the check 'if ( uart->irq > 0 )' in
> > > > ns16550_init_postirq().
> > > > +         * If the check is true then interrupt mode will be used
> > > > otherwise
> > > > +         * ( when irq = 0 )polling.
> > > > +         */
> > > I wonder in how far that's actually correct outside of x86. On x86
> > > IRQ0 is
> > > always the timer interrupt, but I'm not convinced something similar
> > > can be
> > > used as kind of a heuristic on Arm, RISC-V, or basically any other
> > > architecture.
> > I wondered the same. On Arm we are fine because the UART will be an
> > SPI
> > which starts at 32.
> >
> > That's part why I was suggesting to use a define. Because we don't
> > have
> > to hardcode the poll value everywhere.
> Probably then it would be better to introduce 'bool is_polling_mode'
> inside struct ns16550?
I would be OK with that.

Cheers,

--
Julien Grall