linux-kernel - Re: [PATCH anybus v3 4/6] bus: support HMS Anybus-S bus

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Message-ID: <CAK8P3a1q-09=5z4KZPWdpT-T=Tg244HpyN1Cd5=0pDGkQV7aPA@mail.gmail.com>
Date:   Thu, 8 Nov 2018 17:54:10 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     thesven73@...il.com
Cc:     svendev@...x.com, Rob Herring <robh+dt@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Lee Jones <lee.jones@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Andreas Färber <afaerber@...e.de>,
        Thierry Reding <treding@...dia.com>,
        David Lechner <david@...hnology.com>, noralf@...nnes.org,
        Johan Hovold <johan@...nel.org>,
        Michal Simek <monstr@...str.eu>, michal.vokac@...ft.com,
        gregkh <gregkh@...uxfoundation.org>,
        John Garry <john.garry@...wei.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Robin Murphy <robin.murphy@....com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Sebastien Bourdelin <sebastien.bourdelin@...oirfairelinux.com>,
        Icenowy Zheng <icenowy@...c.io>,
        Stuart Yoder <stuyoder@...il.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>
Subject: Re: [PATCH anybus v3 4/6] bus: support HMS Anybus-S bus

On Thu, Nov 8, 2018 at 4:47 PM Sven Van Asbroeck <thesven73@...il.com> wrote:
> On Thu, Nov 8, 2018 at 9:07 AM Arnd Bergmann <arnd@...db.de> wrote:
> > I see this is called from the interrupt handler at the moment, which
> > means you cannot call sleeping functions, but it also means that
> > the timeout may never happen because the timer tick IRQ cannot
> > get through. That means you may have to change the irq handler
> > logic, e.g. to try this a few times but then defer to a bottom half
> > if it fails for a long time.
>
> Touche ! Yes, this is very likely a big problem.
>
> What if I converted the interrupt handler into a threaded interrupt handler?
> That would allow the timer tick to get through, correct?

Yes, with a threaded IRQ handler, the tick comes through, and you can
use a sleeping function to back off between the retries.

        Arnd