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

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Message-ID: <20220208143316.GE112838@ediswmail.ad.cirrus.com>
Date:   Tue, 8 Feb 2022 14:33:16 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     Mark Brown <broonie@...nel.org>
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 01:56:20PM +0000, Mark Brown wrote:
> On Tue, Feb 08, 2022 at 01:50:36PM +0000, Charles Keepax wrote:
> > 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.

Eek.. what a courageous choice. I guess that might work as
long as there is only a single IRQ status bit in the register,
if there are multiple bits this really needs more complex
handling, like you basically need the old behaviour for the
IRQ part of the register, and the new behaviour for the not
IRQ part of the register. So perhaps a new mask to denote which
bit of the register is being used for IRQ stuff?

Thanks,
Charles