linux-kernel - Re: [PATCH 2/2] drm/msm/dp: Return IRQ

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Date:   Wed, 25 Jan 2023 15:36:58 -0800
From:   Kuogee Hsieh <quic_khsieh@...cinc.com>
To:     Doug Anderson <dianders@...omium.org>
CC:     Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>,
        "Javier Martinez Canillas" <javierm@...hat.com>,
        Johan Hovold <johan+linaro@...nel.org>,
        Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
        Sean Paul <sean@...rly.run>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] drm/msm/dp: Return IRQ_NONE for unhandled interrupts


On 1/25/2023 10:21 AM, Doug Anderson wrote:
> Hi,
>
> On Wed, Jan 25, 2023 at 9:22 AM Kuogee Hsieh <quic_khsieh@...cinc.com> wrote:
>>> -void dp_ctrl_isr(struct dp_ctrl *dp_ctrl)
>>> +irqreturn_t dp_ctrl_isr(struct dp_ctrl *dp_ctrl)
>>>    {
>>>        struct dp_ctrl_private *ctrl;
>>>        u32 isr;
>>> +     irqreturn_t ret = IRQ_NONE;
>>>
>>>        if (!dp_ctrl)
>>> -             return;
>>> +             return IRQ_NONE;
>>>
>>>        ctrl = container_of(dp_ctrl, struct dp_ctrl_private, dp_ctrl);
>>>
>>>        isr = dp_catalog_ctrl_get_interrupt(ctrl->catalog);
>> can you add (!isr) check and return IRQ_NONE here to be consistent with
>> dp_aux_isr()?
> I could, though it doesn't really buy us a whole lot in this case and
> just adds an extra test that's not needed. Here it should be easy for
> someone reading the function to see that if "isr == 0" that neither of
> the two "if" statements below will fire and we'll return "IRQ_NONE"
> anyway.
>
> ...that actually made me go back and wonder whether we still needed
> the "if" test in dp_aux_isr() or if it too was also redundant. It
> turns out that it's not! The previous patch made dp_aux_irq() detect
> unexpected interrupts. Thus the "if (!isr)" test earlier is important
> because otherwise we'd end up WARNing "Unexpected interrupt:
> 0x00000000" which would be confusing.
>
> So unless you or others feel strongly that I should add the redundant
> test here, I'd rather keep it off. Let me know.
>
> -Doug
ack