linux-kernel - Re: [PATCH V1 08/15] spmi: pmic_arb: use appropriate flow handler

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Date:   Tue, 06 Jun 2017 16:27:49 +0530
From:   kgunda@...eaurora.org
To:     Stephen Boyd <sboyd@...eaurora.org>
Cc:     Abhijeet Dharmapurikar <adharmap@...eaurora.org>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        David Collins <collinsd@...eaurora.org>,
        Subbaraman Narayanamurthy <subbaram@...eaurora.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        adharmap@...cinc.com, aghayal@....qualcomm.com,
        linux-arm-msm-owner@...r.kernel.org
Subject: Re: [PATCH V1 08/15] spmi: pmic_arb: use appropriate flow handler

On 2017-06-01 00:33, Stephen Boyd wrote:
> On 05/30, Kiran Gunda wrote:
>> From: Abhijeet Dharmapurikar <adharmap@...eaurora.org>
>> 
>> The current code uses handle_level_irq flow handler even if the
>> trigger type of the interrupt is edge. This can lead to missing
>> of an edge transition that happens when the interrupt is being
>> handled. The level flow handler masks the interrupt while it is
>> being handled, so if an edge transition happens at that time,
>> that edge is lost.
>> 
>> Use an edge flow handler for edge type interrupts which ensures
>> that the interrupt stays enabled while being handled - at least
>> until it triggers at which point the flow handler sets the
>> IRQF_PENDING flag and only then masks the interrupt. That
>> IRQF_PENDING state indicates an edge transition happened while
>> the interrupt was being handled and the handler is called again.
>> 
>> Signed-off-by: Abhijeet Dharmapurikar <adharmap@...eaurora.org>
>> Signed-off-by: Kiran Gunda <kgunda@...eaurora.org>
> 
> Do we have any edge interrupts in the tree right now? At least
> RTC seems to be using edge... This should go back to stable with
> a Fixes tag.
> 
Yes. A bunch of internal drivers use edge interrupts.
>> ---
>>  drivers/spmi/spmi-pmic-arb.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>> 
>> diff --git a/drivers/spmi/spmi-pmic-arb.c 
>> b/drivers/spmi/spmi-pmic-arb.c
>> index 1d23df0..ad34491 100644
>> --- a/drivers/spmi/spmi-pmic-arb.c
>> +++ b/drivers/spmi/spmi-pmic-arb.c
>> @@ -625,6 +625,12 @@ static int qpnpint_irq_set_type(struct irq_data 
>> *d, unsigned int flow_type)
>>  	}
>> 
>>  	qpnpint_spmi_write(d, QPNPINT_REG_SET_TYPE, &type, sizeof(type));
>> +
>> +	if (flow_type & IRQ_TYPE_EDGE_BOTH)
> 
> IRQ_TYPE_EDGE_BOTH doesn't seem appropriate to use here. We're
> really just testing to see if the type is an edge type, not if
> it's BOTH edges.
> 
Ok. Agree. Will fix in the follow up patch.
>> +		irq_set_handler_locked(d, handle_edge_irq);
>> +	else
>> +		irq_set_handler_locked(d, handle_level_irq);
>> +
> 
> And we already have code that does that check:
> 
> 	if (flow_type & (IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING))
> 
> so just put the irq_set_handler_locked() calls in those if
> statements please.
Sure. Will fix in the follow up patch.