linux-kernel - Re: [PATCH RESEND RFC 1/4] drivers: pinctrl: qcom: add wakeup capability to GPIO

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Message-ID: <20180802021057.GC6422@codeaurora.org>
Date:   Wed, 1 Aug 2018 20:10:57 -0600
From:   Lina Iyer <ilina@...eaurora.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Marc Zyngier <marc.zyngier@....com>, swboyd@...omium.org,
        evgreen@...omium.org, linus.walleij@...aro.org,
        rplsssn@...eaurora.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, rnayak@...eaurora.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH RESEND RFC 1/4] drivers: pinctrl: qcom: add wakeup
 capability to GPIO

On Wed, Aug 01 2018 at 16:38 -0600, Bjorn Andersson wrote:
>On Wed 01 Aug 12:45 PDT 2018, Lina Iyer wrote:
>
>> Thanks for the feedback, Marc.
>>
>> On Wed, Aug 01 2018 at 00:31 -0600, Marc Zyngier wrote:
>> > On Wed, 01 Aug 2018 03:00:18 +0100,
>> > Lina Iyer <ilina@...eaurora.org> wrote:
>[..]
>> > Why isn't that the case? And if that's because the HW is broken and
>> > doesn't buffer edge interrupts, why can't you use the resend mechanism
>> > instead?
>> >
>> The PDC hardware can replay the interrupts accurately. However, it will
>> replay only the pin and its not the TLMM summary IRQ. The handler here,
>> needs to notify the driver that the wakeup interrupt happened and needs
>> to take action. If I could trip the summary IRQ in this handler that
>> would work too. Can it be done?
>>
>
>Does this means that the intr_status_reg will not hold the information
>about the interrupt events that occurred before we powered on the TLMM
>again? Or is the problem limited to it not triggering the TLMM IRQ?
>
It doesn't. The TLMM is in low power state and cannot sense interrupts.

>Can the PDC (and MPM) be used in the non-sleep use cases as well?
>
Yes. We use PDC to modify polarity of falling edge and low level
interrupts to rising edge and high level interrupt so they may be sensed
at the GIC. I am not sure about the MPM. I suspect it is not.

-- Lina