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

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Message-ID: <5363c7b7-7a5b-490c-445b-fb7ccd693c63@linux.intel.com>
Date:   Fri, 12 May 2023 11:34:44 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Charles Keepax <ckeepax@...nsource.cirrus.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 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/