On 8/17/2021 5:30 AM, Andrew Jeffery wrote:
> Hi Chris,
>
> On Tue, 17 Aug 2021, at 20:47, Chris Chen (TPI) wrote:
>> Hi Andrew,
>>
>> That means I'm able to choose one of following 2 options to achieve
>> pass-through behavior when I using x86-power-control package, is my
>> understanding correct?
>>
>> 1. Add code to re-enable GPIOP0 and GPIOP1 into a pass-through function
>> after they are requested as a GPIO function in the x86-power-control
>> package. (Or maybe to create a script with "devmem > 0x1e6e24BC 32
>> 0x0F000000" command that will be run automatically after system up to
>> change register directly.)
>
> This is a hack and should be a last resort. Even then I'd avoid it.
>
> Certainly you should avoid shipping with /dev/mem enabled.
>
>>
>> 2. Modify pinctrl in Kernel that will not disable GPIOP0 and GPIOP1's
>> pass-through function if they already are configured as a pass-through
>> when they are requesting as a GPIO function.
>
> Perhaps, though maybe you should follow up on whether you can drive
> GPIOP1 when it's in pass-through mode. My recollection is you cannot,
> at least for the AST2500 and earlier, in which case both P0 and P1 are
> effectively inputs for the purpose of the GPIO controller despite P1
> being a physical output. This behaviour is probably more confusing than
> it is helpful.
>
> There's also option 3 which is to emulate the pass-through in software,
> as I outlined in my previous email.
This is some of the configuration that I have on my system where the
pass-through is working correctly in x86-power-control:
I have one kernel patch that selects the "pass-through" pin
configuration on startup:
https://urldefense.com/v3/__https://github.com/Intel-BMC/linux/commit/8fe1ac31c13a0e8443c665394112ba407c90ae70__;!!HSntlCg!Ep_IWFI6dHqTAFsDwLYoJ0JYl3PjsE2hcEJQFIkNt1nDgHL9PvJEAWMmDWtE4az1$
.
In x86-power-control, I have the POWER_BUTTON GPIO mapped to GPIOP2, and
I'm able to claim and monitor that GPIO without affecting the
pass-through status.
I have POWER_OUT mapped to GPIOP3 which cannot be held in
x86-power-control as it disables the pass-through when claimed. So, it
is always released after the power-control action is completed.
Thanks,
-Jason
>
> Hope that helps,
>
> Andrew
>