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

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Date:   Tue, 18 Dec 2018 11:01:51 -0700
From:   Lina Iyer <ilina@...eaurora.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>, evgreen@...omium.org,
        marc.zyngier@....com, linux-kernel@...r.kernel.org,
        rplsssn@...eaurora.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, thierry.reding@...il.com
Subject: Re: [RFC v3 2/3] dt-bindings: sdm845-pinctrl: add wakeup interrupt
 parent for GPIO

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.
>