Re: [RFC v3 2/3] dt-bindings: sdm845-pinctrl: add wakeup interrupt parent for GPIO

[Lina Iyer]

On Mon, Dec 03 2018 at 16:48 -0700, Stephen Boyd wrote:
> Quoting Lina Iyer (2018-11-30 10:33:17)
> > On Thu, Nov 29 2018 at 14:45 -0700, Lina Iyer wrote:
> > >On Wed, Nov 28 2018 at 17:25 -0700, Bjorn Andersson wrote:
> > >>On Wed 28 Nov 09:39 PST 2018, Lina Iyer wrote:
> > >>
> > >>>On Tue, Nov 27 2018 at 14:45 -0700, Stephen Boyd wrote:
> > >>>> Quoting Lina Iyer (2018-11-27 10:21:23)
> > >>>> > On Tue, Nov 27 2018 at 02:12 -0700, Stephen Boyd wrote:
> >
> > [...]
> > >BTW, I am discussing with the internal folks here on if we need to mask
> > >TLMM when the wakeup-parent is MPM. If we don't have to, we should be
> > >able to follow the same model as we done in this patch and don't even
> > >have to check the compatible or use the approach suggested by Stephen.
> > >
> > The TLMM and the MPM are not active at the same time. However, there is
> > a small chance they might be (a few clock cycles) when the system is
> > going down, but even then, since we replay the interrupt from the MPM
> > driver before the interrupts are serviced by Linux, we would not see
> > multiple GPIO interrupts.
> >
> > The way we have MPM working downstream, for a wakeup GPIO IRQ -
> >
> > a. Application cores gets a wakeup interrupt either from RPM or GIC (if
> > TLMM was not powered down) while still in the interrupt locked context.
> >
> > b. In the hardware, apps core handshakes with the RPM and then starts
> > resuming from the platform's system idle driver.
> >
> > c. The first CPU to wake up calls MPM driver from the idle driver, which
> > reads the shared memory to find the MPM pins that are set. Converts the
> > MPM pins to their corresponding linux interrupt and replays the
> > interrupt.
> >
> > d. Idle driver exits and wakeup GPIO interrupt is handled.
> >
> > The MPM pins are not updated after the RPM lets the application core to
> > run. Since TLMM is functional after the RPM handshake, it takes over.
>
> Thanks for the background info. I don't think it really changes anything
> that we've discussed though. We still need to mask the IRQ in TLMM all
> the time when we're using the PDC and we need to leave it unmasked and
> replay edges that the MPM sees when we use the MPM. Should I clean up my
> RFC patch and post it to the list?
I have started to work on this. But feel free to post your version if
you have it ready.

Thanks for the review Stephen. I think I understand now where you are
getting with it. Sorry about all the back and forth.

Thanks,
Lina

> I'd like to see hierarchical gpio
> irqs work in general for this problem and also the SSBI/SPMI gpio irq
> problem that Linus pointed out last week.