linux-kernel - Re: [PATCH 1/4] Irqchip: Ingenic: Change interrupt handling form cascade to chained

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Date:   Sun, 27 Jan 2019 10:21:40 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Zhou Yanjie <zhouyanjie@...o.com>
Cc:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, robh+dt@...nel.org,
        paul.burton@...s.com, mark.rutland@....com, jason@...edaemon.net,
        tglx@...utronix.de, syq@...ian.org, jiaxun.yang@...goat.com,
        772753199@...com
Subject: Re: [PATCH 1/4] Irqchip: Ingenic: Change interrupt handling form cascade to chained_irq.

On Sat, 26 Jan 2019 15:38:40 +0000,
Zhou Yanjie <zhouyanjie@...o.com> wrote:
> 
> The interrupt handling method is changed from old-style cascade to
> chained_irq which is more appropriate. Also, it can process the
> corner situation that more than one irq is coming to a single
> chip at the same time.
> 
> Signed-off-by: Zhou Yanjie <zhouyanjie@...o.com>
> ---
>  drivers/irqchip/irq-ingenic.c | 49 ++++++++++++++++++++++---------------------
>  1 file changed, 25 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-ingenic.c b/drivers/irqchip/irq-ingenic.c
> index 2ff0898..2713ec4 100644
> --- a/drivers/irqchip/irq-ingenic.c
> +++ b/drivers/irqchip/irq-ingenic.c
> @@ -1,16 +1,7 @@
> +// SPDX-License-Identifier: GPL-2.0
>  /*
>   *  Copyright (C) 2009-2010, Lars-Peter Clausen <lars@...afoo.de>
> - *  JZ4740 platform IRQ support
> - *
> - *  This program is free software; you can redistribute it and/or modify it
> - *  under  the terms of the GNU General	 Public License as published by the
> - *  Free Software Foundation;  either version 2 of the License, or (at your
> - *  option) any later version.
> - *
> - *  You should have received a copy of the GNU General Public License along
> - *  with this program; if not, write to the Free Software Foundation, Inc.,
> - *  675 Mass Ave, Cambridge, MA 02139, USA.
> - *
> + *  Ingenic XBurst platform IRQ support
>   */
>  
>  #include <linux/errno.h>
> @@ -19,6 +10,7 @@
>  #include <linux/interrupt.h>
>  #include <linux/ioport.h>
>  #include <linux/irqchip.h>
> +#include <linux/irqchip/chained_irq.h>
>  #include <linux/irqchip/ingenic.h>
>  #include <linux/of_address.h>
>  #include <linux/of_irq.h>
> @@ -41,22 +33,35 @@ struct ingenic_intc_data {
>  #define JZ_REG_INTC_PENDING	0x10
>  #define CHIP_SIZE		0x20
>  
> -static irqreturn_t intc_cascade(int irq, void *data)
> +static void ingenic_chained_handle_irq(struct irq_desc *desc)
>  {
> -	struct ingenic_intc_data *intc = irq_get_handler_data(irq);
> -	uint32_t irq_reg;
> +	struct ingenic_intc_data *intc = irq_desc_get_handler_data(desc);
> +	struct irq_chip *chip = irq_desc_get_chip(desc);
> +	bool have_irq = false;
> +	u32 pending;
>  	unsigned i;
>  
> +	chained_irq_enter(chip, desc);
>  	for (i = 0; i < intc->num_chips; i++) {
> -		irq_reg = readl(intc->base + (i * CHIP_SIZE) +
> +		pending = readl(intc->base + (i * CHIP_SIZE) +
>  				JZ_REG_INTC_PENDING);
> -		if (!irq_reg)
> +		if (!pending)
>  			continue;
>  
> -		generic_handle_irq(__fls(irq_reg) + (i * 32) + JZ4740_IRQ_BASE);
> +		have_irq = true;
> +		while (pending) {
> +			int bit = __ffs(pending);

So 'bit' is the least significant bit in the pending word,

> +
> +			generic_handle_irq(__fls(pending) + (i * 32) +

and here you handle the *most significant* bit,

> +					JZ4740_IRQ_BASE);
> +			pending &= ~BIT(bit);

yet it is the least significant bit that you clear. I am tempted to
say that you have never tested this code with more than a single
interrupt.

Thanks,

	M.

-- 
Jazz is not dead, it just smell funny.