linux-kernel - Re: [PATCH v3] pinctrl: qcom: Handle broken/missing PDC dual edge IRQs on sc7180

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Message-ID: <ac694b7ad8ff6b7563475e014acde1cb@kernel.org>
Date:   Tue, 14 Jul 2020 16:09:27 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     linus.walleij@...aro.org, rnayak@...eaurora.org,
        mkshah@...eaurora.org, ilina@...eaurora.org, cychiang@...omium.org,
        swboyd@...omium.org, bjorn.andersson@...aro.org, agross@...nel.org,
        linux-arm-msm@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] pinctrl: qcom: Handle broken/missing PDC dual edge
 IRQs on sc7180

On 2020-07-14 16:04, Douglas Anderson wrote:
> Depending on how you look at it, you can either say that:
> a) There is a PDC hardware issue (with the specific IP rev that exists
>    on sc7180) that causes the PDC not to work properly when configured
>    to handle dual edges.
> b) The dual edge feature of the PDC hardware was only added in later
>    HW revisions and thus isn't in all hardware.
> 
> Regardless of how you look at it, let's work around the lack of dual
> edge support by only ever letting our parent see requests for single
> edge interrupts on affected hardware.
> 
> NOTE: it's possible that a driver requesting a dual edge interrupt
> might get several edges coalesced into a single IRQ.  For instance if
> a line starts low and then goes high and low again, the driver that
> requested the IRQ is not guaranteed to be called twice.  However, it
> is guaranteed that once the driver's interrupt handler starts running
> its first instruction that any new edges coming in will cause the
> interrupt to fire again.  This is relatively commonplace for dual-edge
> gpio interrupts (many gpio controllers require software to emulate
> dual edge with single edge) so client drivers should be setup to
> handle it.
> 
> Fixes: e35a6ae0eb3a ("pinctrl/msm: Setup GPIO chip in hierarchy")
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

Reviewed-by: Marc Zyngier <maz@...nel.org>

Linus, I assume you will get this one via the pinctrl tree once you
are happy with it?

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...