linux-kernel - Re: [PATCH] irqchip/loongson-pch-pic: Update interrupt registration policy

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Message-ID: <875xyccu1n.ffs@tglx>
Date: Sun, 25 Feb 2024 18:50:28 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Tianyang Zhang <zhangtianyang@...ngson.cn>, chenhuacai@...nel.org,
 jiaxun.yang@...goat.com
Cc: linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org, Baoqi Zhang
 <zhangbaoqi@...ngson.cn>, Zhang Tianyang <zhangtianyang@...ngson.cn>, Biao
 Dong <dongbiao@...ngson.cn>
Subject: Re: [PATCH] irqchip/loongson-pch-pic: Update interrupt registration
 policy

On Fri, Feb 23 2024 at 18:26, Tianyang Zhang wrote:
> From: Baoqi Zhang <zhangbaoqi@...ngson.cn>
>
> We have removed the fixed mapping between the 7A interrupt source
> and the HT interrupt vector, and replaced it with a dynamically
> allocated approach. This will be more conducive to fully utilizing
> existing vectors to support more devices

You are describing _WHAT_ the patch is doing, but you fail to explain
the context and the _WHY_.

> Signed-off-by: Baoqi Zhang <zhangbaoqi@...ngson.cn>
> Signed-off-by: Zhang Tianyang <zhangtianyang@...ngson.cn>
> Signed-off-by: Biao Dong <dongbiao@...ngson.cn>

This Signed-off-by chain is wrong. You, Tianyang, are sending this,
right?

See

https://www.kernel.org/doc/html/latest/process/submitting-patches.html#sign-your-work-the-developer-s-certificate-of-origin

and the following chapters.

> ---
>  drivers/irqchip/irq-loongson-pch-pic.c | 64 +++++++++++++++++++-------
>  1 file changed, 47 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/irqchip/irq-loongson-pch-pic.c b/drivers/irqchip/irq-loongson-pch-pic.c
> index 63db8e2172e0..86549356e76e 100644
> --- a/drivers/irqchip/irq-loongson-pch-pic.c
> +++ b/drivers/irqchip/irq-loongson-pch-pic.c

> @@ -34,6 +34,8 @@
>  #define PIC_REG_IDX(irq_id)	((irq_id) / PIC_COUNT_PER_REG)
>  #define PIC_REG_BIT(irq_id)	((irq_id) % PIC_COUNT_PER_REG)
>  
> +#define hwirq_to_bit(priv, hirq)	(((priv)->table)[(hirq)])

Make this a static inline please.

>  static int nr_pics;
>  
>  struct pch_pic {
> @@ -46,6 +48,8 @@ struct pch_pic {
>  	u32			saved_vec_en[PIC_REG_COUNT];
>  	u32			saved_vec_pol[PIC_REG_COUNT];
>  	u32			saved_vec_edge[PIC_REG_COUNT];
> +	u8			table[PIC_COUNT];
> +	int			inuse;
>  };
>  
>  static struct pch_pic *pch_pic_priv[MAX_IO_PICS];
> @@ -80,45 +84,47 @@ static void pch_pic_mask_irq(struct irq_data *d)
>  {
>  	struct pch_pic *priv = irq_data_get_irq_chip_data(d);
>  
> -	pch_pic_bitset(priv, PCH_PIC_MASK, d->hwirq);
> +	pch_pic_bitset(priv, PCH_PIC_MASK, hwirq_to_bit(priv, d->hwirq));
>  	irq_chip_mask_parent(d);
>  }
>  
>  static void pch_pic_unmask_irq(struct irq_data *d)
>  {
> +	int bit = hwirq_to_bit(priv, d->hwirq);
>  	struct pch_pic *priv = irq_data_get_irq_chip_data(d);

How does this even compile?

>  
> -	writel(BIT(PIC_REG_BIT(d->hwirq)),
> -			priv->base + PCH_PIC_CLR + PIC_REG_IDX(d->hwirq) * 4);
> +	writel(BIT(PIC_REG_BIT(bit)),
> +			priv->base + PCH_PIC_CLR + PIC_REG_IDX(bit) * 4);
>  
>  	irq_chip_unmask_parent(d);
> -	pch_pic_bitclr(priv, PCH_PIC_MASK, d->hwirq);
> +	pch_pic_bitclr(priv, PCH_PIC_MASK, bit);
>  }
>  
>  static int pch_pic_set_type(struct irq_data *d, unsigned int type)
>  {
> +	int bit = hwirq_to_bit(priv, d->hwirq);
>  	struct pch_pic *priv = irq_data_get_irq_chip_data(d);

And this?

By chance because you used a macro instead of an inline function. But
it's still incorrect and wrong.

> @@ -157,6 +164,7 @@ static int pch_pic_domain_translate(struct irq_domain *d,
>  					unsigned long *hwirq,
>  					unsigned int *type)
>  {
> +	int i;
>  	struct pch_pic *priv = d->host_data;
>  	struct device_node *of_node = to_of_node(fwspec->fwnode);

Please see:

https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#variable-declarations
  
> @@ -171,6 +179,20 @@ static int pch_pic_domain_translate(struct irq_domain *d,
>  			return -EINVAL;
>  
>  		*hwirq = fwspec->param[0] - priv->gsi_base;
> +
> +		raw_spin_lock(&priv->pic_lock);

This was clearly never tested with lockdep enabled. Why?

Because lockdep would have told you that this takes the spinlock with
interrupts enabled while it is taken in the mask()/unmask() callbacks
from hard interrupt context.

> +		for (i = 0; i < priv->inuse; i++) {
> +			if (priv->table[i] == *hwirq) {
> +				*hwirq = i;
> +				break;
> +			}
> +		}
> +		if (i == priv->inuse && priv->inuse < PIC_COUNT) {
> +			priv->table[priv->inuse] = *hwirq;
> +			*hwirq = priv->inuse++;
> +		}

So in case that priv->inuse == PIC_COUNT this does not set hwirq and
returns with bogus values.

> +		raw_spin_unlock(&priv->pic_lock);
> +
> @@ -294,6 +320,10 @@ static int pch_pic_init(phys_addr_t addr, unsigned long size, int vec_base,
>  	if (!priv->base)
>  		goto free_priv;
>  
> +	priv->inuse = 0;
> +	for (i = 0; i < PIC_COUNT; i++)
> +		priv->table[i] = -1;

table is an array of u8. So how does -1 make sense? Even if it would
make sense, then you can't ever have 256 interrupts in use because the
truncated -1 is equivalent to hwirq 255.

Thanks,

        tglx