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Re: [PATCH v6 1/2] ns16550: use poll mode if INTERRUPT_LINE is 0xff
- To: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 20 May 2022 11:47:02 +0200
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Fri, 20 May 2022 09:47:10 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 20.05.2022 10:53, 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>
> Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> Changes in v6:
> - wrap the check in additional CONFIG_X86, with appropriate comment
Thanks, albeit ...
> --- a/xen/drivers/char/ns16550.c
> +++ b/xen/drivers/char/ns16550.c
> @@ -1238,6 +1238,17 @@ 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;
>
> +#ifdef CONFIG_X86
> + /* PCI Local Bus Specification Revision 3.0 defines 0xff
> value
> + * as special only for X86 */
... I'll have to remember to correct the style of the comment while
committing ...
> + if ( uart->irq == 0xff )
> + uart->irq = 0;
> +#endif
> + if ( !uart->irq )
> + printk(XENLOG_INFO
> + "ns16550: %pp no legacy IRQ, using poll mode\n",
... and perhaps insert another colon after %pp here.
Jan
> + &PCI_SBDF(0, b, d, f));
> +
> return 0;
> }
> }
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