Re: [Xen-devel] [for-4.7 1/5] drivers/pl011: ACPI: The interrupt should always be high level triggered

[Julien Grall <julien.grall@xxxxxxx>]

Hi Shannon,

Thank you for the review.

On 07/04/16 13:30, Shannon Zhao wrote:
> On 2016/4/7 18:59, Julien Grall wrote:
> > The SPCR does not specify if the interrupt is edge or level triggered.
> > So the configuration needs to be hardcoded in the code.
> >
> > Based on the PL011 TRM (see 2.2.8 in ARM DDI 0183G), the interrupt generated
> > will be active high. This wording implies the interrupt should be high level
> > triggered.
> I think active high can stand rising edge triggered for edge triggered
> interrupt.
>
> E.g. see "Table 5-118 Flag Definitions: Virtual Timer, EL2 timers, and
> Secure & Non-Secure EL1 timers" in ACPI SPEC 6.0.
I've spoken with multiple person about the wording and the consensus is 
"active high" would imply high level triggered. So it's very ambiguous.
However, the PL011 is always using a high level triggered. You can look 
at the device tree bindings such as the one for the foundation model.
Also, the SBSA (section 4.3.2 in ARM-DEN-0029 v2.3) states the PL011 
implemented with a level triggered interrupt.
Note, I wasn't able to get the serial console working on my platform 
with edge triggered interrupt.
Regards,

--
Julien Grall

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