linux-kernel - Re: [PATCH v2 04/11] ASoC: cs42l42: Split probe() and remove() into stages

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Date:   Thu, 15 Sep 2022 13:20:22 +0100
From:   Richard Fitzgerald <rf@...nsource.cirrus.com>
To:     Martin Povišer <povik+lin@...ebit.org>,
        James Schulman <james.schulman@...rus.com>,
        David Rhodes <david.rhodes@...rus.com>,
        "Lucas Tanure" <tanureal@...nsource.cirrus.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>
CC:     Charles Keepax <ckeepax@...nsource.cirrus.com>,
        ChiYuan Huang <cy_huang@...htek.com>,
        Matt Flax <flatmax@...tmax.com>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        - <patches@...nsource.cirrus.com>, <alsa-devel@...a-project.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <asahi@...ts.linux.dev>
Subject: Re: [PATCH v2 04/11] ASoC: cs42l42: Split probe() and remove() into
 stages

On 15/09/2022 10:44, Martin Povišer wrote:
> From: Richard Fitzgerald <rf@...nsource.cirrus.com>
> 
> To prepare for adding SoundWire the probe must be split into three
> parts:
> 
> 1) The bus-specific probe
> 2) Common bus-agnostic probe steps
> 3) Initialization of the peripheral registers
> 
> Step (3) must be separate because on SoundWire devices the probe must
> enable power supplies and release reset so that the peripheral can be
> enumerated by the bus, but it isn't possible to access registers until
> enumeration has completed.
> 
> The call to devm_snd_soc_register_component() must be done at stage (2)
> so that it can EPROBE_DEFER if necessary. In SoundWire systems stage (3)
> is not a probe event so a deferral at this stage would not result in
> re-probing dependencies.
> 
> A new init_done flag indicates that the chip has been identified and
> initialized. This is used to prevent cs42l42_remove(), cs42l42_suspend(),
> cs42l42_restore() and cs42l42_irq_thread() from attempting register
> accesses if the chip was not successfully initialized. Although this
> cannot happen on I2C, because the entire probe would fail, it is
> possible on SoundWire if probe succeeds but the cs42l42 is never
> enumerated.
> 
> Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
> Signed-off-by: Martin Povišer <povik+lin@...ebit.org>
> ---
>   sound/soc/codecs/cs42l42.c | 127 +++++++++++++++++++++++++------------
>   sound/soc/codecs/cs42l42.h |   2 +
>   2 files changed, 87 insertions(+), 42 deletions(-)
> 
> diff --git a/sound/soc/codecs/cs42l42.c b/sound/soc/codecs/cs42l42.c
> index 11cb659f03e0..427b29db2252 100644
> --- a/sound/soc/codecs/cs42l42.c
> +++ b/sound/soc/codecs/cs42l42.c
> @@ -1627,7 +1627,7 @@ static irqreturn_t cs42l42_irq_thread(int irq, void *data)
>   	int report = 0;
>   
>   	mutex_lock(&cs42l42->irq_lock);
> -	if (cs42l42->suspended) {
> +	if (cs42l42->suspended || !cs42l42->init_done) {
>   		mutex_unlock(&cs42l42->irq_lock);
>   		return IRQ_NONE;
>   	}

This doesn't apply to broonie/for-next. Needs rebasing onto commit:
ea75deef1a73 ("ASoC: cs42l42: Only report button state if there was a
button interrupt")