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    SubjectRe: [v2] i2c: mediatek: Move suspend and resume handling to NOIRQ phase
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    On Thu, 2020-12-10 at 15:03 +0200, Grygorii Strashko wrote:
    >
    > On 10/12/2020 03:56, Qii Wang wrote:
    > > On Mon, 2020-12-07 at 18:35 +0200, Grygorii Strashko wrote:
    > >>
    > >>>
    > >>> On Thu, 2020-12-03 at 10:01 +0200, Grygorii Strashko wrote:
    > >>>>
    > >>>> On 03/12/2020 03:25, Qii Wang wrote:
    > >>>>> On Wed, 2020-12-02 at 16:35 +0100, Wolfram Sang wrote:
    > >>>>>> Hi,
    > >>>>>>
    > >>>>>>> Some i2c device driver indirectly uses I2C driver when it is now
    > >>>>>>> being suspended. The i2c devices driver is suspended during the
    > >>>>>>> NOIRQ phase and this cannot be changed due to other dependencies.
    > >>>>>>> Therefore, we also need to move the suspend handling for the I2C
    > >>>>>>> controller driver to the NOIRQ phase as well.
    > >>>>>>>
    > >>>>>>> Signed-off-by: Qii Wang <qii.wang@mediatek.com>
    > >>>>>>
    > >>>>>> Is this a bugfix and should go into 5.10? Or can it wait for 5.11?
    > >>>>>>
    > >>>>>
    > >>>>> Yes, Can you help to apply it into 5.10? Thanks
    > >>>>
    > >>>> To be honest if you still do have any i2c device which accessing i2c buss after _noirq
    > >>>> stage and your driver does not implement .master_xfer_atomic() - you definitely have a bigger problem.
    > >>>> So adding IRQF_NO_SUSPEND sound like a hack and probably works just by luck.
    > >>>>
    > >>>
    > >>> At present, it is only a problem caused by missing interrupts,
    > >>> and .master_xfer_atomic() just a implement in polling mode. Why not set
    > >>> the interrupt to a state that can always be triggered?
    > >>>
    > >>>
    > >>
    > >> Because you must not use any IRQ driven operations after _noirq suspend state as it might (and most probably will)
    > >> cause unpredictable behavior later in suspend_enter():
    > >>
    > >> arch_suspend_disable_irqs();
    > >> BUG_ON(!irqs_disabled());
    > >> ^after this point any IRQ driven I2C transfer will cause IRQ to be re-enabled
    > >>
    > >> if you need turn off device from platform callbacks - .master_xfer_atomic() has to be implemented and used.
    > >>
    > > Maybe my comment is a bit disturbing.Our purpose is not to call i2c and
    > > use interrupts after _noirq pauses.So We use
    > > i2c_mark_adapter_suspended&i2c_mark_adapter_resumed to block these i2c
    > > transfers, There will not have any IRQ driven I2C transfer after this
    > > point:
    > > arch_suspend_disable_irqs();
    > > BUG_ON(!irqs_disabled());
    > > But some device driver will do i2c transfer after
    > > dpm_noirq_resume_devices in dpm_resume_noirq(PMSG_RESUME) when our
    > > driver irq hasn't resume.
    > > void dpm_resume_noirq(pm_message_t state)
    > > {
    > > dpm_noirq_resume_devices(state);
    >
    > Just to clarify. You have resume sequence in dpm_noirq_resume_devices
    > dpm_noirq_resume_devices -> resume I2C -> resume some device -> do i2c transfer after?
    >

    Yes.

    > Is "some device" in Kernel mainline?
    >

    The problematic device driver is drivers/regulator/da9211-regulator.c in
    Kernel mainline.

    > > resume_device_irqs();
    > > device_wakeup_disarm_wake_irqs();
    > > cpuidle_resume();
    > > }
    > > .master_xfer_atomic() seems to be invalid for this question at this
    > > time?
    > >
    >

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