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From: Arnd Bergmann <arnd@kernel.org>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	Viresh Kumar <vireshk@kernel.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Cornelia Huck <cohuck@redhat.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"open list:DRM DRIVER FOR QEMU'S CIRRUS DEVICE" 
	<virtualization@lists.linux-foundation.org>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	Marc Zyngier <maz@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Enrico Weigelt, metux IT consult" <info@metux.net>,
	Jason Wang <jasowang@redhat.com>,
	Stratos Mailing List <stratos-dev@op-lists.linaro.org>
Subject: Re: [Stratos-dev] [PATCH V4 2/2] gpio: virtio: Add IRQ support
Date: Mon, 9 Aug 2021 09:55:07 +0200	[thread overview]
Message-ID: <CAK8P3a3TabswETDAUec-2rbiNBk_K48-UdpTA5Ckvu5ogOyHjQ@mail.gmail.com> (raw)
In-Reply-To: <20210809073020.y6ruibdm37xnx7hg@vireshk-i7>

On Mon, Aug 9, 2021 at 9:30 AM Viresh Kumar <viresh.kumar@linaro.org> wrote:
>
> On 06-08-21, 10:00, Arnd Bergmann wrote:
> > On Fri, Aug 6, 2021 at 9:44 AM Viresh Kumar via Stratos-dev
> > <stratos-dev@op-lists.linaro.org> wrote:
> > >
> > > On 05-08-21, 15:10, Arnd Bergmann wrote:
> > > > I hope this can still be simplified by working out better which state
> > > > transitions are needed exactly. In particular, I would expect that we
> > > > can get away with not sending a VIRTIO_GPIO_MSG_IRQ_TYPE
> > > > for 'mask' state changes at all, but use that only for forcing 'enabled'
> > > > state changes.
> > >
> > > Something like this ?
> >
> > > static void virtio_gpio_irq_mask(struct irq_data *d)
> > > {
> > >         /* Nothing to do here */
> > > }
> >
> > You'd have to do /something/ here I think, if only setting the flag
> > that we don't want to deliver the next interrupt.
> >
> > > static void virtio_gpio_irq_unmask(struct irq_data *d)
> > > {
> > >         struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
> > >         struct virtio_gpio *vgpio = gpiochip_get_data(gc);
> > >
> > >         /* Queue the buffer unconditionally on unmask */
> > >         virtio_gpio_irq_prepare(vgpio, d->hwirq);
> > > }
> >
> > And check the flag here to not requeue it if it's masked.
>
> I am not sure I understand why this would be required. If the
> interrupt is getting disabled, then unmask will not get called here
> and so we won't requeue anything. Same will happen with threaded
> handlers where the interrupt gets unmasked at a later point of time.

Ah, right. There is already a flag that gets checked by the caller.

It does feel odd to have an empty 'irq_mask' callback though, so
maybe there is still something missing, just not what I thought.

It's probably the result of calling handle_level_irq(), which as you
said is closer to what we want, but is not exactly what we need for
this protocol.

        Arnd

  reply	other threads:[~2021-08-09  7:55 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-03 11:36 [PATCH V4 0/2] gpio: Add virtio based driver Viresh Kumar
2021-08-03 11:36 ` [PATCH V4 1/2] gpio: Add virtio-gpio driver Viresh Kumar
2021-08-03 11:36 ` [PATCH V4 2/2] gpio: virtio: Add IRQ support Viresh Kumar
2021-08-03 15:01   ` Arnd Bergmann
2021-08-04  7:05     ` Viresh Kumar
2021-08-04  8:27       ` Arnd Bergmann
2021-08-05  7:05         ` Viresh Kumar
2021-08-05 11:26     ` Viresh Kumar
     [not found]     ` <0100017b1610f711-c53c79f2-9e28-4c45-bb42-8db09688b18e-000000@email.amazonses.com>
2021-08-05 12:03       ` [Stratos-dev] " Arnd Bergmann
2021-08-05 12:49         ` Viresh Kumar
2021-08-05 13:10           ` Arnd Bergmann
2021-08-06  7:44             ` Viresh Kumar
     [not found]             ` <0100017b1a6c0a05-e41dc16c-b326-4017-a63d-a24a6c1fde70-000000@email.amazonses.com>
2021-08-06  8:00               ` Arnd Bergmann
2021-08-09  7:30                 ` Viresh Kumar
2021-08-09  7:55                   ` Arnd Bergmann [this message]
2021-08-09 10:46                     ` Viresh Kumar
     [not found]                     ` <0100017b2a85eaf8-08b905fc-89f7-43a4-857e-070ca9691ce1-000000@email.amazonses.com>
2021-08-09 11:19                       ` Arnd Bergmann
2021-08-10  7:35                         ` Viresh Kumar

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