Gpio in vexpress

Gpio in vexpress

[ido berenbaum]

[-- Attachment #1: Type: text/plain, Size: 413 bytes --]

Hi, I was trying to understand the architecture of the vexpress virtual
machine in regards to adding new gpios that are going to be external.
First, is it right to act as if I am developing on a physical board and add
the gpios to the VexpressMachineState struct?
Secondly, which gpio type fits here? I see that for fsl_imx7 it is the
imx_gpio, but what is for vexpress? Should I create one?
Or, can I use pl061?

[-- Attachment #2: Type: text/html, Size: 499 bytes --]

Re: Gpio in vexpress

[Peter Maydell]

On Tue, 16 May 2023 at 07:36, ido berenbaum <ido.ber3@gmail.com> wrote:
>
> Hi, I was trying to understand the architecture of the vexpress virtual machine in regards to adding new gpios that are going to be external.
> First, is it right to act as if I am developing on a physical board and add the gpios to the VexpressMachineState struct?
> Secondly, which gpio type fits here? I see that for fsl_imx7 it is the imx_gpio, but what is for vexpress? Should I create one?
> Or, can I use pl061?

The vexpress is a model of a real piece of hardware, so the
answer is "you model what the real hardware is doing". You
should be able to find that out in the technical reference
manual for the board / daughterboard.

Why are you interested in the vexpress in particular?
It is a pretty elderly development board...

thanks
-- PMM

Re: Gpio in vexpress

[ido berenbaum]

[-- Attachment #1: Type: text/plain, Size: 1494 bytes --]

Oh, I was under the impression the vexpress board is not based on a real
physical hardware like virt.
In any case, In my workplace we use the qemu for our CI testing, to prevent
the need to use our hardware for logical tests.
The thing is our SoC is not implemented in qemu, and so we are using the
vexpress as it is similar enough when considering the core structure.
But, as it is not identical we need to make changes to make it fit our use
cases. For example, add a gpio.

Do you think we should use a different SoC as a base for our development?

On Tue, May 16, 2023, 12:17 Peter Maydell <peter.maydell@linaro.org> wrote:

> On Tue, 16 May 2023 at 07:36, ido berenbaum <ido.ber3@gmail.com> wrote:
> >
> > Hi, I was trying to understand the architecture of the vexpress virtual
> machine in regards to adding new gpios that are going to be external.
> > First, is it right to act as if I am developing on a physical board and
> add the gpios to the VexpressMachineState struct?
> > Secondly, which gpio type fits here? I see that for fsl_imx7 it is the
> imx_gpio, but what is for vexpress? Should I create one?
> > Or, can I use pl061?
>
> The vexpress is a model of a real piece of hardware, so the
> answer is "you model what the real hardware is doing". You
> should be able to find that out in the technical reference
> manual for the board / daughterboard.
>
> Why are you interested in the vexpress in particular?
> It is a pretty elderly development board...
>
> thanks
> -- PMM
>

[-- Attachment #2: Type: text/html, Size: 2089 bytes --]

Re: Gpio in vexpress

[Peter Maydell]

On Thu, 18 May 2023 at 15:36, ido berenbaum <ido.ber3@gmail.com> wrote:
>
> Oh, I was under the impression the vexpress board is not based on a real physical hardware like virt.

Yep; the motherboard part is documented here:
https://developer.arm.com/documentation/dui0447/latest/
and the daughterboards are:
https://developer.arm.com/documentation/dui0448/latest/ (A9)
https://developer.arm.com/documentation/dui0604/latest/ (A15)

> In any case, In my workplace we use the qemu for our CI testing, to prevent the need to use our hardware for logical tests.
> The thing is our SoC is not implemented in qemu, and so we are using the vexpress as it is similar enough when considering the core structure.
> But, as it is not identical we need to make changes to make it fit our use cases. For example, add a gpio.
>
> Do you think we should use a different SoC as a base for our development?

If you're just doing local hacks you can do whatever
you like. Upstream we won't take changes which don't
match the real vexpress hardware, and that didn't include
any GPIO controllers.

If the guest code you're running is expecting to run on
your actual SoC you might consider modelling it, but
this is a fair amount of work.

thanks
-- PMM