linux-kernel - Re: [PATCH 01/10] soundwire: bus: Allow SoundWire peripherals to register IRQ handlers

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Date:   Fri, 12 May 2023 16:43:40 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
CC:     <broonie@...nel.org>, <lee@...nel.org>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <conor+dt@...nel.org>,
        <tglx@...utronix.de>, <maz@...nel.org>, <linus.walleij@...aro.org>,
        <vkoul@...nel.org>, <lgirdwood@...il.com>,
        <yung-chuan.liao@...ux.intel.com>, <sanyog.r.kale@...el.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 01/10] soundwire: bus: Allow SoundWire peripherals to
 register IRQ handlers

On Fri, May 12, 2023 at 11:34:44AM -0500, Pierre-Louis Bossart wrote:
> 
> 
> On 5/12/23 11:02, Charles Keepax wrote:
> > On Fri, May 12, 2023 at 08:45:51AM -0500, Pierre-Louis Bossart wrote:
> >>> @@ -1711,6 +1739,9 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave)
> >>>  				struct device *dev = &slave->dev;
> >>>  				struct sdw_driver *drv = drv_to_sdw_driver(dev->driver);
> >>>  
> >>> +				if (slave->prop.use_domain_irq && slave->irq)
> >>> +					handle_nested_irq(slave->irq);
> >>> +
> >>
> >> I am a bit lost here, I can understand that alerts would be handled by a
> >> dedicated handler, but here the code continues and will call the
> >> existing interrupt_callback.
> >>
> >> Is this intentional? I wonder if there's a risk with two entities
> >> dealing with the same event and programming the same registers.
> >> Shouldn't there be some sort of 'either or' rule?
> >>
> > 
> > I guess there is a risk of them "handling" the IRQ twice,
> > although it is hard to see why you would write the driver that
> > way. Also since they are sequencial the second would I guess
> > just see that no IRQs are pending.
> > 
> > The intention for calling both is that it facilitates using
> > the same IRQ handler for I2C and SoundWire. At least on the
> > Cirrus devices there are a bunch of chip specific registers
> > that need treated exactly the same on I2C and SoundWire, but
> > then a couple of extra registers that need handled in the
> > SoundWire case. This way the handling of those can be kept
> > completely in the SoundWire part of the code and not ifdef-ed
> > into the main IRQ path.
> 
> Sounds good to me, but it's worth adding a comment and improving the
> commit message with design intent/rules since it's a common part in
> drivers/soundwire/

Yeah no issues with updating the commit message to explain that
in more detail.

Thanks,
Charles