linux-kernel - Re: [PATCH 07/10] irqchip/cs42l43: Add support for the cs42l43 IRQs

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Date:   Fri, 12 May 2023 15:39:33 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     Marc Zyngier <maz@...nel.org>
CC:     <broonie@...nel.org>, <lee@...nel.org>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <conor+dt@...nel.org>,
        <tglx@...utronix.de>, <linus.walleij@...aro.org>,
        <vkoul@...nel.org>, <lgirdwood@...il.com>,
        <yung-chuan.liao@...ux.intel.com>, <sanyog.r.kale@...el.com>,
        <pierre-louis.bossart@...ux.intel.com>,
        <alsa-devel@...a-project.org>, <patches@...nsource.cirrus.com>,
        <devicetree@...r.kernel.org>, <linux-gpio@...r.kernel.org>,
        <linux-spi@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/10] irqchip/cs42l43: Add support for the cs42l43 IRQs

On Fri, May 12, 2023 at 04:10:05PM +0100, Marc Zyngier wrote:
> On Fri, 12 May 2023 13:28:35 +0100,
> Charles Keepax <ckeepax@...nsource.cirrus.com> wrote:
> > 
> > The CS42L43 is an audio CODEC with integrated MIPI SoundWire interface
> > (Version 1.2.1 compliant), I2C, SPI, and I2S/TDM interfaces designed
> > for portable applications. It provides a high dynamic range, stereo
> > DAC for headphone output, two integrated Class D amplifiers for
> > loudspeakers, and two ADCs for wired headset microphone input or
> > stereo line input. PDM inputs are provided for digital microphones.
> > 
> > The IRQ chip provides IRQ functionality both to other parts of the
> > cs42l43 device and to external devices that wish to use its IRQs.
> 
> Sorry, but this isn't much of an interrupt controller driver. A modern
> interrupt controller driver is firmware-driven (DT or ACPI, pick your
> poison), uses irq domains, and uses the irqchip API.
> 

Apologies but I really need a little help clarifying the issues
here. I am totally happy to fix things up but might need a couple
pointers.

1) uses the irqchip API / uses irq domains

The driver does use both the irqchip API and domains, what
part of the IRQ API are we not using that we should be?

The driver registers an irq domain using
irq_domain_create_linear.  It requests its parent IRQ using
request_threaded_irq. It passes IRQs onto the devices requesting
IRQs from it using handle_nested_irq and irq_find_mapping.

Is the objection here that regmap is making these calls for us,
rather than them being hard coded into this driver?

2) driver is firmware-driven (DT or ACPI, pick your poison)

The irq chip has representation in firmware, in fact we have
tested this on both ACPI and DT. Other devices can request
IRQs from it through firmware, same as they can for any other
IRQ chip.

Is the objection here the table mapping the register fields that
are provided as an IRQ on the device?

Thanks kindly for your review and help,
Charles