linux-kernel - Re: [PATCH v2] regmap-irq: Use regmap_irq_update_bits instead of regmap

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Message-ID: <YgJ2hG2vwUclA/zF@sirena.org.uk>
Date:   Tue, 8 Feb 2022 13:56:20 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Charles Keepax <ckeepax@...nsource.cirrus.com>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Prasad Kumpatla <quic_pkumpatl@...cinc.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>,
        'Linux Samsung SOC' <linux-samsung-soc@...r.kernel.org>
Subject: Re: [PATCH v2] regmap-irq: Use regmap_irq_update_bits instead of
 regmap_write

On Tue, Feb 08, 2022 at 01:50:36PM +0000, Charles Keepax wrote:

> Apologies for the multiple emails, yeah looking at this I think
> need some more information on how the hardware that patch was
> addressing works. I don't quite understand what was wrong with
> the old code even in the inverted case, the old code wrote a 1 to
> every bit except the interrupt being cleared which gets a 0. This
> feels like how I would have thought a write 0 to clear IRQ would
> work, you don't want to clear any other bits so you write 1 to
> them.

> The update_bits is really problematic as even in the write 0 to
> clear case, if a new interrupt asserts between the regmap_read
> and regmap_write that make up the update_bits, you will clear that
> new interrupt without ever noticing it.

My understanding was that they'd mixed interrupt handling in as a
bitfield in another register.

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