linux-kernel - Re: [PATCH 5/7] regulator: qcom-labibb: Implement short-circuit and over-current IRQs

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Date:   Mon, 11 Jan 2021 20:14:08 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     linux-arm-msm@...r.kernel.org, agross@...nel.org,
        bjorn.andersson@...aro.org, lgirdwood@...il.com,
        robh+dt@...nel.org, sumit.semwal@...aro.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        phone-devel@...r.kernel.org, konrad.dybcio@...ainline.org,
        marijn.suijten@...ainline.org, martin.botka@...ainline.org
Subject: Re: [PATCH 5/7] regulator: qcom-labibb: Implement short-circuit and
 over-current IRQs

Il 11/01/21 14:57, Mark Brown ha scritto:
> On Sat, Jan 09, 2021 at 02:29:19PM +0100, AngeloGioacchino Del Regno wrote:
> 
>> +	/* If the regulator is not enabled, this is a fake event */
>> +	if (!ops->is_enabled(vreg->rdev))
>> +		return 0;
> 
> Or handling the interrupt raced with a disable initiated from elsewhere.
> Does the hardware actually have a problem with reporting spurious errors?
> 
>> +	return ret ? IRQ_NONE : IRQ_HANDLED;
> 
> Here and elsewhere please write normal conditional statements to improve
> legibility.
> 
No problem. Will do.

>> +	/* This function should be called only once, anyway. */
>> +	if (unlikely(vreg->ocp_irq_requested))
>> +		return 0;
> 
> If this is not a fast path it doesn't need an unlikely() annotation;
> indeed it sounds more like there should be a warning printed if this
> isn't supposed to be called multiple times.
> 
That was extra-paranoid safety, looking at this one again, that should 
be totally unnecessary.
I think that removing this check entirely would be just fine also 
because.. anyway.. writing to these registers more than once won't do 
any harm, nor break functionality: I mean, even if it happens for 
whatever reason, there's *no real need* to avoid it from the hw perspective.

>> +	/* IRQ polarities - LAB: trigger-low, IBB: trigger-high */
>> +	if (vreg->type == QCOM_LAB_TYPE) {
>> +		irq_flags |= IRQF_TRIGGER_LOW;
>> +		irq_trig_low = 1;
>> +	} else {
>> +		irq_flags |= IRQF_TRIGGER_HIGH;
>> +		irq_trig_low = 0;
>> +	}
> 
> This would be more clearly written as a switch statement.
> 
A switch statement looked like being a bit "too much" for just two cases 
where vreg->type cannot be anything else but QCOM_LAB_TYPE or 
QCOM_IBB_TYPE... but okay, let's write a switch statement in place of that.

>> +	return devm_request_threaded_irq(vreg->dev, vreg->ocp_irq, NULL,
>> +					 qcom_labibb_ocp_isr, irq_flags,
>> +					 ocp_irq_name, vreg);
> 
> Are you *sure* that devm_ is appropriate here and the interrupt handler
> won't attempt to use things that will be deallocated before devm gets
> round to freeing the interrupt?
> 
Yeah, I'm definitely sure.

>> +		if (!!(val & LABIBB_CONTROL_ENABLE)) {
> 
> The !! is redundant here and makes things less clear.
> 
My bad, I forgot to clean this one up before sending.

>> @@ -166,8 +560,37 @@ static int qcom_labibb_of_parse_cb(struct device_node *np,
>>   				   struct regulator_config *config)
>>   {
>>   	struct labibb_regulator *vreg = config->driver_data;
>> +	char *sc_irq_name;
> 
> I really, really wouldn't expect to see interrupts being requested in
> the DT parsing callback - apart from anything else the device is going
> to have the physical interrupts with or without DT binding information.
> These callbacks are for regulator specific properties, not basic probing.
> Just request the interrupts in the main probe function, this also means
> you can avoid using all the DT specific APIs which are generally a
> warning sign.
> 

...And I even wrote a comment saying "The Short Circuit interrupt is 
critical: fail if not found"!!! Whoa! That was bad.
Yeah, I'm definitely moving that to the appropriate place.