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From: Andrew Lunn <andrew@lunn.ch>
To: "Marek Behún" <kabel@kernel.org>
Cc: "Gregory CLEMENT" <gregory.clement@bootlin.com>,
	"Rui Salvaterra" <rsalvaterra@gmail.com>,
	"Uwe Kleine-König" <uwe@kleine-koenig.org>,
	linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org
Subject: Re: [PATCH mvebu-dt] ARM: dts: turris-omnia: configure LED[2]/INTn pin as interrupt pin
Date: Sun, 21 Feb 2021 22:18:48 +0100	[thread overview]
Message-ID: <YDLOOMW+VEhchh7n@lunn.ch> (raw)
In-Reply-To: <20210221014756.7c444c08@kernel.org>

> BTW do you have some experience where pca9538 or compatible cause
> errors when used for interrupts? Because I am thinking about trying
> to update the pca953x driver to support IRQs via the gpio_chip it
> registers, instead of a separate irq_chip.

I had a board which just died at boot with an interrupt storm. It was
probably a PCA9554, at least, i have that datasheet in my collection.

First off, the hardware needs to designed correctly. All unused pins
need a pull up/down since they default to inputs, and hence will
trigger interrupts. Or you need to make unused pins outputs before you
enable interrupts. And that probably goes against the design of the
GPIO subsystem. I don't think you actually know when a pin is unused.

I'm not sure i would want to touch this driver. Given how badly this
device implements interrupts, any board which does successfully use it
for interrupts might regress if you make code changes. And then you
are going to have to try to figure out what you actually changed and
why it regressed.

    Andrew

WARNING: multiple messages have this Message-ID (diff)
From: Andrew Lunn <andrew@lunn.ch>
To: "Marek Behún" <kabel@kernel.org>
Cc: stable@vger.kernel.org,
	"Gregory CLEMENT" <gregory.clement@bootlin.com>,
	linux-arm-kernel@lists.infradead.org,
	"Uwe Kleine-König" <uwe@kleine-koenig.org>,
	"Rui Salvaterra" <rsalvaterra@gmail.com>
Subject: Re: [PATCH mvebu-dt] ARM: dts: turris-omnia: configure LED[2]/INTn pin as interrupt pin
Date: Sun, 21 Feb 2021 22:18:48 +0100	[thread overview]
Message-ID: <YDLOOMW+VEhchh7n@lunn.ch> (raw)
In-Reply-To: <20210221014756.7c444c08@kernel.org>

> BTW do you have some experience where pca9538 or compatible cause
> errors when used for interrupts? Because I am thinking about trying
> to update the pca953x driver to support IRQs via the gpio_chip it
> registers, instead of a separate irq_chip.

I had a board which just died at boot with an interrupt storm. It was
probably a PCA9554, at least, i have that datasheet in my collection.

First off, the hardware needs to designed correctly. All unused pins
need a pull up/down since they default to inputs, and hence will
trigger interrupts. Or you need to make unused pins outputs before you
enable interrupts. And that probably goes against the design of the
GPIO subsystem. I don't think you actually know when a pin is unused.

I'm not sure i would want to touch this driver. Given how badly this
device implements interrupts, any board which does successfully use it
for interrupts might regress if you make code changes. And then you
are going to have to try to figure out what you actually changed and
why it regressed.

    Andrew

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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2021-02-21 21:19 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-20 23:11 [PATCH mvebu-dt] ARM: dts: turris-omnia: configure LED[2]/INTn pin as interrupt pin Marek Behún
2021-02-20 23:11 ` Marek Behún
2021-02-21  0:10 ` Andrew Lunn
2021-02-21  0:10   ` Andrew Lunn
2021-02-21  0:47   ` Marek Behún
2021-02-21  0:47     ` Marek Behún
2021-02-21 21:18     ` Andrew Lunn [this message]
2021-02-21 21:18       ` Andrew Lunn
2021-02-21 22:40       ` Marek Behún
2021-02-21 22:40         ` Marek Behún
2021-02-21 19:58 ` Rui Salvaterra
2021-02-21 19:58   ` Rui Salvaterra
2021-02-21 20:52 ` Andrew Lunn
2021-02-21 20:52   ` Andrew Lunn
2021-02-21 20:58   ` Marek Behún
2021-02-21 20:58     ` Marek Behún
2021-04-02 20:15 ` Gregory CLEMENT
2021-04-02 20:15   ` Gregory CLEMENT

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