[RESEND PATCH] pinctrl: rockchip: Disable interrupt when changing it's capability
jeffy.chen at rock-chips.com
Mon May 7 19:56:48 PDT 2018
On 05/08/2018 10:31 AM, JeffyChen wrote:
> Hi Brian,
> On 05/08/2018 09:56 AM, Brian Norris wrote:
>> On Tue, May 08, 2018 at 09:36:24AM +0800, Jeffy Chen wrote:
>>> On 05/08/2018 06:15 AM, Brian Norris wrote:
>>>> On the other hand...this also implies there may be a race condition
>>>> there, where we might lose an interrupt if there is an edge between the
>>>> re-configuration of the polarity in rockchip_irq_demux() and the
>>>> clearing/handling of the interrupt (handle_edge_irq() ->
>>>> chip->irq_ack()). If we have an edge between there, then we might ack
>>>> it, but leave the polarity such that we aren't ready for the next
>>>> (inverted) edge.
>>> if let me guess, the unexpected irq we saw is the hardware trying to
>>> losing irq? for example, we set a EDGE_RISING, and the hardware saw
>>> the gpio
>>> is already high, then though it might lost an irq, so fake one for safe?
>> I won't pretend to know what the IC designers were doing, but I don't
>> think that would resolve the problem I'm talking about. The sequence is
>> something like:
>> 1. EDGE_BOTH IRQ occurs (e.g., low to high)
>> 2. reconfigure polarity in rockchip_irq_demux() (polarity=low)
>> 3. continue to handle_edge_irq()
>> 4. another HW edge occurs (e.g., high to low)
>> 5. handle_edge_irq() (from 3) acks (clears) IRQ (before a subsequent
>> rockchip_irq_demux() gets a chance to run and flip the polarity)
>> Now the polarity is still low, but the next trigger should be a
>> low-to-high edge.
> oops, i see the problem.
> so what if we do these:
> 1/ edge irq triggered
> 2/ read gpio level
> 3/ handle irq(ack irq)
> 4/ toggle edge mode(with a while gpio level check)
> if the gpio changed in 2/ -> 3/, the 4/ will trigger an irq when writing
> GPIO_INT_POLARITY(which is what we are trying to avoid in the set_type
> but this would not work if i'm wrong about how the HW fake an irq when
> changing POLARITY...
> or maybe we could just check the gpio status again after
> handle_edge_irq, and correct the polarity in this case
i saw the pinctrl-msm.c do this in the ack(),
and also at the end of set_type(), which might avoid another race in the
>>> i'll try to confirm it with IC guys.
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