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


  • To: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
  • From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Date: Wed, 11 May 2022 16:40:15 +0200
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  • Cc: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
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  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On Wed, May 11, 2022 at 02:35:05PM +0000, Andrew Cooper wrote:
> On 11/05/2022 15:15, Roger Pau Monné wrote:
> > 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>
> 
> TBH, can be fixed on commit, save another round of patching.

Indeed, thanks for taking care of that.

Roger.



 


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