linux-kernel - Re: [PATCH 2/4] media: rkisp1: Fix IRQ handler return values

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Message-ID: <CAHCN7xJcYACscBHExh6n-kAKofrk=E2VTncm8Y_ZmWjcj_yzPA@mail.gmail.com>
Date:   Tue, 5 Dec 2023 06:35:08 -0600
From:   Adam Ford <aford173@...il.com>
To:     Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc:     Dafna Hirschfeld <dafna@...tmail.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Paul Elder <paul.elder@...asonboard.com>,
        Alexander Stein <alexander.stein@...tq-group.com>,
        kieran.bingham@...asonboard.com, umang.jain@...asonboard.com,
        linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] media: rkisp1: Fix IRQ handler return values

On Tue, Dec 5, 2023 at 6:02 AM Tomi Valkeinen
<tomi.valkeinen@...asonboard.com> wrote:
>
> On 05/12/2023 13:57, Adam Ford wrote:
> > On Tue, Dec 5, 2023 at 2:10 AM Tomi Valkeinen
> > <tomi.valkeinen@...asonboard.com> wrote:
> >>
> >> The IRQ handler rkisp1_isr() calls sub-handlers, all of which returns an
> >> irqreturn_t value, but rkisp1_isr() ignores those values and always
> >> returns IRQ_HANDLED.
> >>
> >> Fix this by collecting the return values, and returning IRQ_HANDLED or
> >> IRQ_NONE as appropriate.
> >>
> >> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
> >> ---
> >>   drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c | 18 ++++++++++++++----
> >>   1 file changed, 14 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c b/drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c
> >> index 76f93614b4cf..1d60f4b8bd09 100644
> >> --- a/drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c
> >> +++ b/drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c
> >> @@ -445,17 +445,27 @@ static int rkisp1_entities_register(struct rkisp1_device *rkisp1)
> >>
> >>   static irqreturn_t rkisp1_isr(int irq, void *ctx)
> >>   {
> >> +       irqreturn_t ret;
> >> +
> >>          /*
> >>           * Call rkisp1_capture_isr() first to handle the frame that
> >>           * potentially completed using the current frame_sequence number before
> >>           * it is potentially incremented by rkisp1_isp_isr() in the vertical
> >>           * sync.
> >>           */
> >> -       rkisp1_capture_isr(irq, ctx);
> >> -       rkisp1_isp_isr(irq, ctx);
> >> -       rkisp1_csi_isr(irq, ctx);
> >>
> >> -       return IRQ_HANDLED;
> >> +       ret = IRQ_NONE;
> >> +
> >> +       if (rkisp1_capture_isr(irq, ctx) == IRQ_HANDLED)
> >> +               ret = IRQ_HANDLED;
> >> +
> >> +       if (rkisp1_isp_isr(irq, ctx) == IRQ_HANDLED)
> >> +               ret = IRQ_HANDLED;
> >> +
> >> +       if (rkisp1_csi_isr(irq, ctx) == IRQ_HANDLED)
> >> +               ret = IRQ_HANDLED;
> >> +
> >
> > It seems like we're throwing away the value of ret each time the
> > subsequent if statement is evaluated.  Whether or not they return
> > didn't matter before, and the only one that seems using the return
> > code is the last one.
> >
> > Wouldn't it be simpler to use ret = rkisp1_capture_isr(irq, ctx), ret
> > = rkisp1_isp_isr(irq, ctx) and ret = rkisp1_csi_isr(irq, ctx) if we
> > care about the return code?
> >
> > How do you expect this to return if one of the first two don't return
> > IRQ_HANDLED?
>
> I'm sorry, I don't quite follow what you mean. Can you elaborate a bit?
>
> We want the rkisp1_isr() to return IRQ_NONE if none of the sub-handlers
> handled the interrupt. Otherwise, if any of the sub-handlers return
> IRQ_HANDLED, rkisp1_isr() returns IRQ_HANDLED.

OK.  I understand your explanation.  I retract my comment.  I'll try
to test this series tonight on my imx8mp

adam


>
>   Tomi
>