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

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Date:   Sun, 27 Jan 2019 22:49:51 +0800
From:   Zhou Yanjie <zhouyanjie@...o.com>
To:     Marc Zyngier <marc.zyngier@....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.

My fault, in the function "generic_handle_irq" should use "bit" instead 
of "__fls(irq_reg)".
It will be fixed in the v2.

On 2019年01月27日 18:21, Marc Zyngier wrote:
> 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.
>