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From: Eric Anholt <eric@anholt.net>
To: Rob Herring <robh@kernel.org>, Mark Brown <broonie@kernel.org>
Cc: Stefan Wahren <stefan.wahren@i2se.com>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Scott Branden <sbranden@broadcom.com>,
	Marc Zyngier <marc.zyngier@arm.com>, Ray Jui <rjui@broadcom.com>,
	Alexander Graf <agraf@suse.de>,
	linux-spi@vger.kernel.org, bcm-kernel-feedback-list@broadcom.com,
	linux-rpi-kernel@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] spi: bcm2835aux: ensure interrupts are enabled for shared handler
Date: Thu, 03 May 2018 14:15:32 -0700	[thread overview]
Message-ID: <87efiso2yz.fsf@anholt.net> (raw)
In-Reply-To: <20180503180945.3502-1-robh@kernel.org>


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Rob Herring <robh@kernel.org> writes:

> The BCM2835 AUX SPI has a shared interrupt line (with AUX UART).
> Downstream fixes this with an AUX irqchip to demux the IRQ sources and a
> DT change which breaks compatibility with older kernels. The AUX irqchip
> was already rejected for upstream[1] and the DT change would break
> working systems if the DTB is updated to a newer one. The latter issue
> was brought to my attention by Alex Graf.
>
> The root cause however is a bug in the shared handler. Shared handlers
> must check that interrupts are actually enabled before servicing the
> interrupt. Add a check that the TXEMPTY or IDLE interrupts are enabled.

It looks to me like we'd only return IRQ_HANDLED if we did work that
needed doing.  Is this check effectively doing some interlock to make
sure that we've already started bcm2835aux_spi_transfer_one_irq() and
aren't just racing against transaction setup?

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WARNING: multiple messages have this Message-ID (diff)
From: eric@anholt.net (Eric Anholt)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] spi: bcm2835aux: ensure interrupts are enabled for shared handler
Date: Thu, 03 May 2018 14:15:32 -0700	[thread overview]
Message-ID: <87efiso2yz.fsf@anholt.net> (raw)
In-Reply-To: <20180503180945.3502-1-robh@kernel.org>

Rob Herring <robh@kernel.org> writes:

> The BCM2835 AUX SPI has a shared interrupt line (with AUX UART).
> Downstream fixes this with an AUX irqchip to demux the IRQ sources and a
> DT change which breaks compatibility with older kernels. The AUX irqchip
> was already rejected for upstream[1] and the DT change would break
> working systems if the DTB is updated to a newer one. The latter issue
> was brought to my attention by Alex Graf.
>
> The root cause however is a bug in the shared handler. Shared handlers
> must check that interrupts are actually enabled before servicing the
> interrupt. Add a check that the TXEMPTY or IDLE interrupts are enabled.

It looks to me like we'd only return IRQ_HANDLED if we did work that
needed doing.  Is this check effectively doing some interlock to make
sure that we've already started bcm2835aux_spi_transfer_one_irq() and
aren't just racing against transaction setup?
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  parent reply	other threads:[~2018-05-03 21:15 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-03 18:09 [PATCH] spi: bcm2835aux: ensure interrupts are enabled for shared handler Rob Herring
2018-05-03 18:09 ` Rob Herring
2018-05-03 18:31 ` Stefan Wahren
2018-05-03 18:31   ` Stefan Wahren
2018-05-03 21:15 ` Eric Anholt [this message]
2018-05-03 21:15   ` Eric Anholt
2018-05-03 22:06   ` Rob Herring
2018-05-03 22:06     ` Rob Herring
2018-05-03 22:36     ` Eric Anholt
2018-05-03 22:36       ` Eric Anholt
2018-05-03 23:06 ` Mark Brown
2018-05-03 23:06   ` Mark Brown
2018-05-03 23:19 ` Applied "spi: bcm2835aux: ensure interrupts are enabled for shared handler" to the spi tree Mark Brown
2018-05-03 23:19   ` Mark Brown

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