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[0/2] hw/arm/npcm7xx_gpio: Add some pin state QOM

Message ID 20230406002447.4046378-1-komlodi@google.com
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Series hw/arm/npcm7xx_gpio: Add some pin state QOM | expand

Message

Joe Komlodi April 6, 2023, 12:24 a.m. UTC 
Hi all,

This series adds a couple QOM properties for retrieving and setting pin
state via qom-get and qom-get.

We ran into a situation in multi-SoC simulation where the BMC would need
to update its input pin state based on behavior from the other SoC. It
made the most sense to expose this over QMP, so this adds properties to
allow people to do so.

Since the NPCM7xx is typically used to help manage other SoCs, hopefully
other people will find this useful as well.

Thanks!
Joe

Joe Komlodi (2):
  hw/gpio/npcm7xx: Add GPIO DIN object property
  hw/gpio/npcm7xx: Support qom-get on GPIO pin level

 hw/gpio/npcm7xx_gpio.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

Comments

Peter Maydell April 13, 2023, 12:51 p.m. UTC | #1 
On Thu, 6 Apr 2023 at 01:25, Joe Komlodi <komlodi@google.com> wrote:
>
> Hi all,
>
> This series adds a couple QOM properties for retrieving and setting pin
> state via qom-get and qom-get.
>
> We ran into a situation in multi-SoC simulation where the BMC would need
> to update its input pin state based on behavior from the other SoC. It
> made the most sense to expose this over QMP, so this adds properties to
> allow people to do so.

This does leave the simulation in an odd situation if
the input GPIO was connected to some other device -- the
other device thinks it's put the GPIO line low, but then something
external has reached in and set it to 1, so the two ends of
what is conceptually a single signal line now disagree about
what voltage it's at...

It looks like the hw/gpio/aspeed_gpio device has been here before
you, only that device chose to use one bool property per GPIO
line. It would be nice to be consistent -- if we want to allow
QOM to set/get the GPIO line values, it should be the same
interface regardless of GPIO controller.

-- PMM