Subject: Re: [PATCH 1/2] powerpc/8xx: Fix NR_IRQ bugs and refactor 8xx interrupt controller

From: Benjamin Herrenschmidt <[email-masked]>
Date: Tue, 17 Apr 2012 09:03:02 +1000

On Mon, 2012-04-16 at 14:13 -0600, Grant Likely wrote:
> The mpc8xx driver uses a reference to NR_IRQS that is buggy.  It uses
> NR_IRQs for the array size of the ppc_cached_irq_mask bitmap, but
> NR_IRQs could be smaller than the number of hardware irqs that
> ppc_cached_irq_mask tracks.
> 
> Also, while fixing that problem, it became apparent that the interrupt
> controller only supports 32 interrupt numbers, but it is written as if
> it supports multiple register banks which is more complicated.
> 
> This patch pulls out the buggy reference to NR_IRQs and fixes the size
> of the ppc_cached_irq_mask to match the number of HW irqs.  It also
> drops the now-unnecessary code since ppc_cached_irq_mask is no longer
> an array.

Can you rename ppc_cached_irq_mask while at it ? I think it was written
that way because it was all copy/pasted from powermac/pic.c which -does-
need it to be an array (and has the same bugs btw) :-) 

I wonder if we can get rid of the cached mask alltogether... I have the
feeling that we could just rely on the irq_desc fields nowadays for
that... this code is ancient.

Cheers,
Ben.

> Signed-off-by: Grant Likely <[email-masked]>
> Cc: Benjamin Herrenschmidt <[email-masked]>
> ---
>  arch/powerpc/sysdev/mpc8xx_pic.c |   61 +++++++++++++-------------------------
>  1 file changed, 21 insertions(+), 40 deletions(-)
> 
> diff --git a/arch/powerpc/sysdev/mpc8xx_pic.c b/arch/powerpc/sysdev/mpc8xx_pic.c
> index d5f5416..91cade8 100644
> --- a/arch/powerpc/sysdev/mpc8xx_pic.c
> +++ b/arch/powerpc/sysdev/mpc8xx_pic.c
> @@ -18,69 +18,47 @@
>  extern int cpm_get_irq(struct pt_regs *regs);
>  
>  static struct irq_domain *mpc8xx_pic_host;
> -#define NR_MASK_WORDS   ((NR_IRQS + 31) / 32)
> -static unsigned long ppc_cached_irq_mask[NR_MASK_WORDS];
> +static unsigned long ppc_cached_irq_mask;
>  static sysconf8xx_t __iomem *siu_reg;
>  
>  int cpm_get_irq(struct pt_regs *regs);
>  
> -static void mpc8xx_unmask_irq(struct irq_data *d)
> +static inline unsigned long mpc8xx_irqd_to_bit(struct irq_data *d)
>  {
> -	int	bit, word;
> -	unsigned int irq_nr = (unsigned int)irqd_to_hwirq(d);
> -
> -	bit = irq_nr & 0x1f;
> -	word = irq_nr >> 5;
> +	return 0x80000000 >> irqd_to_hwirq(d);
> +}
>  
> -	ppc_cached_irq_mask[word] |= (1 << (31-bit));
> -	out_be32(&siu_reg->sc_simask, ppc_cached_irq_mask[word]);
> +static void mpc8xx_unmask_irq(struct irq_data *d)
> +{
> +	ppc_cached_irq_mask |= mpc8xx_irqd_to_bit(d);
> +	out_be32(&siu_reg->sc_simask, ppc_cached_irq_mask);
>  }
>  
>  static void mpc8xx_mask_irq(struct irq_data *d)
>  {
> -	int	bit, word;
> -	unsigned int irq_nr = (unsigned int)irqd_to_hwirq(d);
> -
> -	bit = irq_nr & 0x1f;
> -	word = irq_nr >> 5;
> -
> -	ppc_cached_irq_mask[word] &= ~(1 << (31-bit));
> -	out_be32(&siu_reg->sc_simask, ppc_cached_irq_mask[word]);
> +	ppc_cached_irq_mask &= ~mpc8xx_irqd_to_bit(d);
> +	out_be32(&siu_reg->sc_simask, ppc_cached_irq_mask);
>  }
>  
>  static void mpc8xx_ack(struct irq_data *d)
>  {
> -	int	bit;
> -	unsigned int irq_nr = (unsigned int)irqd_to_hwirq(d);
> -
> -	bit = irq_nr & 0x1f;
> -	out_be32(&siu_reg->sc_sipend, 1 << (31-bit));
> +	out_be32(&siu_reg->sc_sipend, mpc8xx_irqd_to_bit(d));
>  }
>  
>  static void mpc8xx_end_irq(struct irq_data *d)
>  {
> -	int bit, word;
> -	unsigned int irq_nr = (unsigned int)irqd_to_hwirq(d);
> -
> -	bit = irq_nr & 0x1f;
> -	word = irq_nr >> 5;
> -
> -	ppc_cached_irq_mask[word] |= (1 << (31-bit));
> -	out_be32(&siu_reg->sc_simask, ppc_cached_irq_mask[word]);
> +	ppc_cached_irq_mask |= mpc8xx_irqd_to_bit(d);
> +	out_be32(&siu_reg->sc_simask, ppc_cached_irq_mask);
>  }
>  
>  static int mpc8xx_set_irq_type(struct irq_data *d, unsigned int flow_type)
>  {
> -	if (flow_type & IRQ_TYPE_EDGE_FALLING) {
> -		irq_hw_number_t hw = (unsigned int)irqd_to_hwirq(d);
> +	/* only external IRQ senses are programmable */
> +	if ((flow_type & IRQ_TYPE_EDGE_FALLING) && !(irqd_to_hwirq(d) & 1)) {
>  		unsigned int siel = in_be32(&siu_reg->sc_siel);
> -
> -		/* only external IRQ senses are programmable */
> -		if ((hw & 1) == 0) {
> -			siel |= (0x80000000 >> hw);
> -			out_be32(&siu_reg->sc_siel, siel);
> -			__irq_set_handler_locked(d->irq, handle_edge_irq);
> -		}
> +		siel |= mpc8xx_irqd_to_bit(d);
> +		out_be32(&siu_reg->sc_siel, siel);
> +		__irq_set_handler_locked(d->irq, handle_edge_irq);
>  	}
>  	return 0;
>  }
> @@ -132,6 +110,9 @@ static int mpc8xx_pic_host_xlate(struct irq_domain *h, struct device_node *ct,
>  		IRQ_TYPE_EDGE_FALLING,
>  	};
>  
> +	if (intspec[0] > 0x1f)
> +		return 0;
> +
>  	*out_hwirq = intspec[0];
>  	if (intsize > 1 && intspec[1] < 4)
>  		*out_flags = map_pic_senses[intspec[1]];