linux-kernel - Re: [PATCH 3/3] pinctrl: qcom: Clear possible pending irq when remuxing GPIOs

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Message-ID: <853f7419653122d2fd46e8d70202d25c@kernel.org>
Date:   Tue, 24 Nov 2020 11:15:10 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Maulik Shah <mkshah@...eaurora.org>
Cc:     Douglas Anderson <dianders@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Linus Walleij <linus.walleij@...aro.org>,
        Srinivas Ramana <sramana@...eaurora.org>,
        Neeraj Upadhyay <neeraju@...eaurora.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        linux-gpio@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Andy Gross <agross@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] pinctrl: qcom: Clear possible pending irq when
 remuxing GPIOs

On 2020-11-24 10:37, Maulik Shah wrote:

[...]

>>   static int msm_pinmux_set_mux(struct pinctrl_dev *pctldev,
>>   			      unsigned function,
>>   			      unsigned group)
>>   {
>>   	struct msm_pinctrl *pctrl = pinctrl_dev_get_drvdata(pctldev);
>> +	struct gpio_chip *gc = &pctrl->chip;
>> +	unsigned int irq = irq_find_mapping(gc->irq.domain, group);
>>   	const struct msm_pingroup *g;
>>   	unsigned long flags;
>>   	u32 val, mask;
>> +	u32 oldval;
>> +	u32 old_i;
>>   	int i;
>>     	g = &pctrl->soc->groups[group];
>> @@ -187,15 +215,26 @@ static int msm_pinmux_set_mux(struct pinctrl_dev 
>> *pctldev,
>>   	if (WARN_ON(i == g->nfuncs))
>>   		return -EINVAL;
>>   -	raw_spin_lock_irqsave(&pctrl->lock, flags);
>> +	disable_irq(irq);
>>   -	val = msm_readl_ctl(pctrl, g);
>> +	raw_spin_lock_irqsave(&pctrl->lock, flags);
>> +	oldval = val = msm_readl_ctl(pctrl, g);
>>   	val &= ~mask;
>>   	val |= i << g->mux_bit;
>>   	msm_writel_ctl(val, pctrl, g);
>> -
>>   	raw_spin_unlock_irqrestore(&pctrl->lock, flags);
>>   +	/*
>> +	 * Clear IRQs if switching to/from GPIO mode since muxing to/from
>> +	 * the GPIO path can cause phantom edges.
>> +	 */
>> +	old_i = (oldval & mask) >> g->mux_bit;
>> +	if (old_i != i &&
>> +	    (i == pctrl->soc->gpio_func || old_i == pctrl->soc->gpio_func))
>> +		msm_pinctrl_clear_pending_irq(pctrl, group, irq);
> 
> disable_irq() and enable_irq() should be moved inside this if loop. as
> only use for this is to mask the IRQ when switching back to gpio IRQ
> mode?
> 
> i also don't think we should leave IRQ enabled at the end of this
> function by default, probably need to check if IRQ was already
> unmasked before disabling it, then only call enable_irq().

Why? It looks to me that this reproduces the behaviour of 
IRQCHIP_SET_TYPE_MASKED, which is highly desirable. What
problem are you trying to address with this?

> 
>> +
>> +	enable_irq(irq);
>> +
>>   	return 0;
>>   }
>>   @@ -456,32 +495,45 @@ static const struct pinconf_ops 
>> msm_pinconf_ops = {
>>   static int msm_gpio_direction_input(struct gpio_chip *chip, unsigned 
>> offset)
>>   {
>>   	const struct msm_pingroup *g;
>> +	unsigned int irq = irq_find_mapping(chip->irq.domain, offset);
>>   	struct msm_pinctrl *pctrl = gpiochip_get_data(chip);
>>   	unsigned long flags;
>> +	u32 oldval;
>>   	u32 val;
>>     	g = &pctrl->soc->groups[offset];
>>   +	disable_irq(irq);
>> +
>>   	raw_spin_lock_irqsave(&pctrl->lock, flags);
>>   -	val = msm_readl_ctl(pctrl, g);
>> +	oldval = val = msm_readl_ctl(pctrl, g);
>>   	val &= ~BIT(g->oe_bit);
>>   	msm_writel_ctl(val, pctrl, g);
>>     	raw_spin_unlock_irqrestore(&pctrl->lock, flags);
>>   +	if (oldval != val)
>> +		msm_pinctrl_clear_pending_irq(pctrl, offset, irq);
>> +
>> +	enable_irq(irq);
> 
> i do not think we need disable_irq() and enable_irq() here, changing
> direction to input does not mean its being used for interrupt only, it
> may be set to use something like Rx mode in UART.
> 
> the client driver should enable IRQ when needed.

And the kernel doesn't expect random interrupts to fire. Again, what
are you trying to fix by removing these?

         M.
-- 
Jazz is not dead. It just smells funny...