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Message-ID: <CAKT61h8EkOOkDHou65Uc7NNomJ6Nowvw8o6JnWxNyc0S_=x_JA@mail.gmail.com>
Date: Fri, 15 Jul 2016 17:44:50 +0800
From: Wan ZongShun <mcuos.com@...il.com>
To: Arnd Bergmann <arnd@...db.de>
Cc: Wan Zongshun <vw@...mu.org>, Jason Cooper <jason@...edaemon.net>,
linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
Russell King <linux@...linux.org.uk>,
devicetree@...r.kernel.org, linux-clk@...r.kernel.org,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Thomas Gleixner <tglx@...utronix.de>,
linux-kernel <linux-kernel@...r.kernel.org>,
Rob Herring <robh@...nel.org>, p.zabel@...gutronix.de
Subject: Re: [PATCH v2 02/10] irqchip: add irqchip driver for nuc900
2016-07-15 15:00 GMT+08:00 Arnd Bergmann <arnd@...db.de>:
> On Friday, July 15, 2016 1:15:58 PM CEST Wan Zongshun wrote:
>>
>> Actually, I have two choice to implement this function:
>>
>> option1:
>>
>> void __exception_irq_entry aic_handle_irq(struct pt_regs *regs)
>> {
>> u32 hwirq;
>>
>> (void)readl(aic_base + REG_AIC_IPER);
>> hwirq = readl(aic_base + REG_AIC_ISNR);
>>
>> handle_IRQ((irq_find_mapping(aic_domain, hwirq)), regs);
>> }
>
> (side note: I think you want handle_domain_irq())
>
>> option2:
>>
>> void __exception_irq_entry aic_handle_irq(struct pt_regs *regs)
>> {
>> u32 hwirq;
>>
>> hwirq = readl(aic_base + REG_AIC_IPER);
>> hwirq <<= 2;
>>
>> handle_IRQ((irq_find_mapping(aic_domain, hwirq)), regs);
>> }
>>
>> Though the option2 do shift for hwirq, but it seems better than do io
>> operation by readl,so I prefer to option2, agree?
>
> That will only return an irq number that is a multiple of four, which
> seems wrong since the numbers are not that. Did you mean to write
>
> hwirq = ilog2(hwirq); ?
Sorry, my fault, I mean hwirq >>= 2, bit[7:2] indicates which irq is triggering.
so I have to do right shift 2 for IPER value.
>
> That assumes that REG_AIC_IPER contains a 32-bit value with one single
> bit set to indicate which IRQ was triggered.
>
> If the difference is only in performance, you could try measuring which
> of the two ends up being faster.
It seems hard to measure. I think Do IO operation should be slower
than shift 2. :)
>
> Arnd
--
---
Vincent Wan(Zongshun)
www.mcuos.com
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