Re: [PATCH 2/2] gpio: mxs: fix duplicate level interrupts

[Marek Vasut]

On 10/21/2016 03:11 PM, Sascha Hauer wrote:
> According to the reference manual level interrupts can't be acked
> using the IRQSTAT registers. The effect is that when a level interrupt
> triggers the following ack is a no-op and the same interrupt triggers
> again right after it has been unmasked after running the interrupt
> handler.
> 
> The reference manual says:
> 
> Status bits for pins configured as level sensitive interrupts cannot be
> cleared unless either the actual pin is in the non-interrupting state, or
> the pin has been disabled as an interrupt source by clearing its bit in
> HW_PINCTRL_PIN2IRQ.
> 
> To work around the duplicated interrupts we can use the PIN2IRQ
> rather than the IRQEN registers to mask the interrupts. This
> probably does not work for the edge interrupts, so we have to split up
> the irq chip into two chip types, one for the level interrupts and
> one for the edge interrupts. We now make use of two different enable
> registers, so we have to take care to always enable the right one,
> especially during switching of the interrupt type. An easy way
> to accomplish this is to use the IRQCHIP_SET_TYPE_MASKED which
> makes sure that set_irq_type is called with masked interrupts. With this
> the flow to change the irq type is like:
> 
> - core masks interrupt (using the current chip type)
> - mxs_gpio_set_irq_type() changes chip type if necessary
> - mxs_gpio_set_irq_type() unconditionally sets the enable bit in the
>   now unused enable register
> - core eventually unmasks the interrupt (using the new chip type)
> 
> Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>

Reviewed-by: Marek Vasut <marex@xxxxxxx>

Thanks for the detailed explanation, that was really needed.

> ---
>  drivers/gpio/gpio-mxs.c | 38 +++++++++++++++++++++++++++++---------
>  1 file changed, 29 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpio/gpio-mxs.c b/drivers/gpio/gpio-mxs.c
> index 1cf579f..62061f7 100644
> --- a/drivers/gpio/gpio-mxs.c
> +++ b/drivers/gpio/gpio-mxs.c
> @@ -87,10 +87,15 @@ static int mxs_gpio_set_irq_type(struct irq_data *d, unsigned int type)
>  	u32 val;
>  	u32 pin_mask = 1 << d->hwirq;
>  	struct irq_chip_generic *gc = irq_data_get_irq_chip_data(d);
> +	struct irq_chip_type *ct = irq_data_get_chip_type(d);
>  	struct mxs_gpio_port *port = gc->private;
>  	void __iomem *pin_addr;
>  	int edge;
>  
> +	if (!(ct->type & type))
> +		if (irq_setup_alt_chip(d, type))
> +			return -EINVAL;
> +
>  	port->both_edges &= ~pin_mask;
>  	switch (type) {
>  	case IRQ_TYPE_EDGE_BOTH:
> @@ -119,10 +124,13 @@ static int mxs_gpio_set_irq_type(struct irq_data *d, unsigned int type)
>  
>  	/* set level or edge */
>  	pin_addr = port->base + PINCTRL_IRQLEV(port);
> -	if (edge & GPIO_INT_LEV_MASK)
> +	if (edge & GPIO_INT_LEV_MASK) {
>  		writel(pin_mask, pin_addr + MXS_SET);
> -	else
> +		writel(pin_mask, port->base + PINCTRL_IRQEN(port) + MXS_SET);
> +	} else {
>  		writel(pin_mask, pin_addr + MXS_CLR);
> +		writel(pin_mask, port->base + PINCTRL_PIN2IRQ(port) + MXS_SET);
> +	}
>  
>  	/* set polarity */
>  	pin_addr = port->base + PINCTRL_IRQPOL(port);
> @@ -202,22 +210,37 @@ static int __init mxs_gpio_init_gc(struct mxs_gpio_port *port, int irq_base)
>  	struct irq_chip_generic *gc;
>  	struct irq_chip_type *ct;
>  
> -	gc = irq_alloc_generic_chip("gpio-mxs", 1, irq_base,
> +	gc = irq_alloc_generic_chip("gpio-mxs", 2, irq_base,
>  				    port->base, handle_level_irq);
>  	if (!gc)
>  		return -ENOMEM;
>  
>  	gc->private = port;
>  
> -	ct = gc->chip_types;
> +	ct = &gc->chip_types[0];
> +	ct->type = IRQ_TYPE_LEVEL_HIGH | IRQ_TYPE_LEVEL_LOW;
> +	ct->chip.irq_ack = irq_gc_ack_set_bit;
> +	ct->chip.irq_mask = irq_gc_mask_disable_reg;
> +	ct->chip.irq_unmask = irq_gc_unmask_enable_reg;
> +	ct->chip.irq_set_type = mxs_gpio_set_irq_type;
> +	ct->chip.irq_set_wake = mxs_gpio_set_wake_irq;
> +	ct->chip.flags = IRQCHIP_SET_TYPE_MASKED;
> +	ct->regs.ack = PINCTRL_IRQSTAT(port) + MXS_CLR;
> +	ct->regs.enable = PINCTRL_PIN2IRQ(port) + MXS_SET;
> +	ct->regs.disable = PINCTRL_PIN2IRQ(port) + MXS_CLR;
> +
> +	ct = &gc->chip_types[1];
> +	ct->type = IRQ_TYPE_EDGE_RISING | IRQ_TYPE_EDGE_FALLING;
>  	ct->chip.irq_ack = irq_gc_ack_set_bit;
>  	ct->chip.irq_mask = irq_gc_mask_disable_reg;
>  	ct->chip.irq_unmask = irq_gc_unmask_enable_reg;
>  	ct->chip.irq_set_type = mxs_gpio_set_irq_type;
>  	ct->chip.irq_set_wake = mxs_gpio_set_wake_irq;
> +	ct->chip.flags = IRQCHIP_SET_TYPE_MASKED;
>  	ct->regs.ack = PINCTRL_IRQSTAT(port) + MXS_CLR;
>  	ct->regs.enable = PINCTRL_IRQEN(port) + MXS_SET;
>  	ct->regs.disable = PINCTRL_IRQEN(port) + MXS_CLR;
> +	ct->handler = handle_level_irq;
>  
>  	irq_setup_generic_chip(gc, IRQ_MSK(32), IRQ_GC_INIT_NESTED_LOCK,
>  			       IRQ_NOREQUEST, 0);
> @@ -298,11 +321,8 @@ static int mxs_gpio_probe(struct platform_device *pdev)
>  	}
>  	port->base = base;
>  
> -	/*
> -	 * select the pin interrupt functionality but initially
> -	 * disable the interrupts
> -	 */
> -	writel(~0U, port->base + PINCTRL_PIN2IRQ(port));
> +	/* initially disable the interrupts */
> +	writel(0, port->base + PINCTRL_PIN2IRQ(port));
>  	writel(0, port->base + PINCTRL_IRQEN(port));
>  
>  	/* clear address has to be used to clear IRQSTAT bits */
> 


-- 
Best regards,
Marek Vasut