Re: [PATCH v4 1/2] ns16550: use poll mode if INTERRUPT_LINE is 0xff

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, May 11, 2022 at 03:59:28PM +0200, Marek Marczykowski-Górecki wrote:
> Intel LPSS has INTERRUPT_LINE set to 0xff by default, that is declared
> by the PCI Local Bus Specification Revision 3.0 (from 2004) as
> "unknown"/"no connection". Fallback to poll mode in this case.
> The 0xff handling is x86-specific, the surrounding code is guarded with
> CONFIG_X86 anyway.
> 
> Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> ---
> Changes in v4:
>  - adjust log message, change it from WARNING to INFO
>  - re-add x86 reference in the commit message
> Changes in v3:
>  - change back to checking 0xff explicitly
>  - adjust commit message, include spec reference
>  - change warning to match the above
> Changes in v2:
>  - add log message
>  - extend commit message
>  - code style fix
> ---
>  xen/drivers/char/ns16550.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
> index fb75cee4a13a..c0d65cff62fe 100644
> --- a/xen/drivers/char/ns16550.c
> +++ b/xen/drivers/char/ns16550.c
> @@ -1238,6 +1238,13 @@ pci_uart_config(struct ns16550 *uart, bool_t skip_amt, 
> unsigned int idx)
>                              pci_conf_read8(PCI_SBDF(0, b, d, f),
>                                             PCI_INTERRUPT_LINE) : 0;
>  
> +                if ( uart->irq == 0xff )
> +                    uart->irq = 0;
> +                if ( !uart->irq )
> +                    printk(XENLOG_INFO
> +                           "ns16550: %pp no legacy IRQ %d, using poll 
> mode\n",
> +                           &PCI_SBDF(0, b, d, f), uart->irq);

There's no point in printing ->irq as it will be 0 or else the message
won't be printed.

With that fixed:

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Thanks.