linux-kernel - Re: [PATCH v2 1/5] drivers: pinctrl: qcom: add wakeup capability to GPIO

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Date:   Mon, 27 Aug 2018 10:56:44 -0600
From:   Lina Iyer <ilina@...eaurora.org>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Hans Verkuil <hverkuil@...all.nl>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>, evgreen@...omium.org,
        rplsssn@...eaurora.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org,
        Rajendra Nayak <rnayak@...eaurora.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Andy Gross <andy.gross@...aro.org>,
        Doug Anderson <dianders@...omium.org>
Subject: Re: [PATCH v2 1/5] drivers: pinctrl: qcom: add wakeup capability to
 GPIO

On Sun, Aug 26 2018 at 08:33 -0600, Linus Walleij wrote:
>On Fri, Aug 17, 2018 at 6:39 PM Lina Iyer <ilina@...eaurora.org> wrote:
>
>> QCOM SoC's that have Power Domain Controller (PDC) chip in the always-on
>> domain can wakeup the SoC, when interrupts and GPIOs are routed to the
>> its interrupt controller. Only select GPIOs that are deemed wakeup
>> capable are routed to specific PDC pins. During low power state, the
>> pinmux interrupt controller may be non-functional but the PDC would be.
>> The PDC can detect the wakeup GPIO is triggered and bring the TLMM to an
>> operational state.
>>
>> Interrupts that are level triggered will be detected at the TLMM when
>> the controller becomes operational. Edge interrupts however need to be
>> replayed again.
>>
>> Request the corresponding PDC IRQ, when the GPIO is requested as an IRQ,
>> but keep it disabled. During suspend, we can enable the PDC IRQ instead
>> of the GPIO IRQ, which may or not be detected.
>>
>> Signed-off-by: Lina Iyer <ilina@...eaurora.org>
>> ---
>> Changes in v1:
>>         - Trigger GPIO in h/w from PDC IRQ handler
>>         - Avoid big tables for GPIO-PDC map, pick from DT instead
>>         - Use handler_data
>
>Just for the record this is an impressive and much needed patch
>set, no other SoC developer has yet taken on the task of making this
>work so I very much appreciate that Qualcomm show the way.
>
>> +static int msm_gpio_pdc_pin_request(struct irq_data *d)
>> +static int msm_gpio_pdc_pin_release(struct irq_data *d)
>> +static int msm_gpio_irq_reqres(struct irq_data *d)
>> +{
>(...)
>> +       if (gpiochip_lock_as_irq(gc, irqd_to_hwirq(d))) {
>(...)
>> +static void msm_gpio_irq_relres(struct irq_data *d)
>> +{
>> +       gpiochip_unlock_as_irq(gc, irqd_to_hwirq(d));
>> +}
>
>FYI Hans Verkuil is working on a patch set that moves the
>lock/unlock as IRQ call to the irqchip request() and release()
>functions so we can switch a GPIO irqchip line from IRQ
>mode to say output at runtime without too much trouble.
>(CEC needs this.)
>
Thanks, I will look into Hans's RFCv2. But what would help me would be
to avoid creating the IRQ for the GPIO itself (I have the latent IRQ),
if I could just return that instead in gpio_to_irq(), it might be
easier. I understand ->to_irq() is supposed to be a translate function
only, I can avoid the dance of enabling and diabling the PDC IRQ on
suspend and resume.

-- Lina

>I suspect that will make your work easier?
>
>Hans can you include Lina in the loop for your patches
>so she can take that into accoun because I think we might
>need that as a base for this.
>
>Yours,
>Linus Walleij