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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>,
	Stratos Mailing List <stratos-dev@op-lists.linaro.org>,
	"Enrico Weigelt, metux IT consult" <info@metux.net>,
	Jason Wang <jasowang@redhat.com>
Subject: Re: [Stratos-dev] [PATCH V4 2/2] gpio: virtio: Add IRQ support
Date: Thu, 5 Aug 2021 14:03:40 +0200	[thread overview]
Message-ID: <CAK8P3a0DWkfQcZpmyfKcdNt1MHf8ha6a9L2LmLt1Tv-j0HDr3w@mail.gmail.com> (raw)
In-Reply-To: <0100017b1610f711-c53c79f2-9e28-4c45-bb42-8db09688b18e-000000@email.amazonses.com>

On Thu, Aug 5, 2021 at 1:26 PM Viresh Kumar via Stratos-dev
<stratos-dev@op-lists.linaro.org> wrote:
>
> On 03-08-21, 17:01, Arnd Bergmann wrote:
> > As far as I can tell, the update_irq_type() message would lead to the
> > interrupt getting delivered when it was armed and is now getting disabled,
> > but I don't see why we would call update_irq_type() as a result of the
> > eventq notification.
>
> Based on discussion we had today (offline), I changed the design a bit
> and used handle_level_irq() instead, as it provides consistent calls
> to mask/unmask(), which simplified the whole thing a bit.

The new flow looks much nicer to me, without the workqueue, and
doing the requeue directly in the unmask() operation.

I don't quite understand the purpose of the type_pending and
mask_pending flags yet, can you explain what they actually
do?

Also, I have no idea about whether using the handle_level_irq()
function is actually correct here. I suppose if necessary, the driver
could provide its own irq.handler callback in place of that.

> Also I have broken the rule from specs, maybe we should update spec
> with that, where the specs said that the buffer must not be queued
> before enabling the interrupt. I just queue the buffer unconditionally
> now from unmask().
>
> I am not sure but there may be some race around the "queued" flag and
> I wonder if we can land in a scenario where the buffer is left
> un-queued somehow, while an interrupt is enabled.

Can that be integrated with the "masked" state now? It looks like
the two flags are always opposites now.

      Arnd

  parent reply	other threads:[~2021-08-05 12:04 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       ` Arnd Bergmann [this message]
2021-08-05 12:49         ` [Stratos-dev] " 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
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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