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From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 02/10] irqchip: add irqchip driver for nuc900
Date: Fri, 15 Jul 2016 12:02:55 +0200	[thread overview]
Message-ID: <1885052.EkH2ZADWZS@wuerfel> (raw)
In-Reply-To: <CAKT61h8EkOOkDHou65Uc7NNomJ6Nowvw8o6JnWxNyc0S_=x_JA@mail.gmail.com>

On Friday, July 15, 2016 5:44:50 PM CEST Wan ZongShun wrote:
> 2016-07-15 15:00 GMT+08:00 Arnd Bergmann <arnd@arndb.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.

Ok, got it.

> > 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. 

It depends on how fast that particular I/O path is. A lot of readl()
operations are awfully slow, but the hardware design for the interrupt
controller may in fact have optimized this to be reasonably fast.

Another option would be to avoid the shift and just use the raw value
of the REG_AIC_IPER register as the hwirq, with a custom map()
callback that turns shifts the number read from the DT two bits
so it matches the register value.

	Arnd

  reply	other threads:[~2016-07-15 10:02 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-10  7:27 [PATCH v2 00/10] ARM: NUC900: Add NUC970 SoC support Wan Zongshun
2016-07-10  7:27 ` [PATCH v2 01/10] ARM: NUC900: Add nuc970 machine support Wan Zongshun
2016-07-10 22:11   ` Arnd Bergmann
2016-07-11 16:04   ` Arnd Bergmann
2016-07-12  4:30     ` Wan Zongshun
2016-07-12  7:14       ` Wan Zongshun
2016-07-12  8:23         ` Arnd Bergmann
2016-07-10  7:27 ` [PATCH v2 02/10] irqchip: add irqchip driver for nuc900 Wan Zongshun
2016-07-10 21:51   ` Paul Gortmaker
2016-07-11  2:19     ` Wan Zongshun
2016-07-11 15:46   ` Arnd Bergmann
2016-07-12  7:04     ` Wan Zongshun
2016-07-12  8:26       ` Arnd Bergmann
2016-07-14  8:52         ` Wan Zongshun
2016-07-14 11:09           ` Arnd Bergmann
2016-07-13 20:09   ` Jason Cooper
2016-07-14  3:36     ` Wan Zongshun
2016-07-14 13:54       ` Jason Cooper
2016-07-15  5:15         ` Wan Zongshun
2016-07-15  7:00           ` Arnd Bergmann
2016-07-15  9:44             ` Wan ZongShun
2016-07-15 10:02               ` Arnd Bergmann [this message]
2016-07-21 18:45                 ` Jason Cooper
2016-07-15 15:45               ` Jason Cooper
2016-07-10  7:27 ` [PATCH v2 03/10] Clocksource: add nuc970 clocksource driver Wan Zongshun
2016-07-11 15:36   ` Arnd Bergmann
2016-07-12  7:32     ` Wan Zongshun
2016-07-12  8:28       ` Arnd Bergmann
2016-07-21 12:52         ` Daniel Lezcano
2016-07-21 12:54           ` Arnd Bergmann
2016-07-10  7:27 ` [PATCH v2 04/10] clk: add Clock driver for nuc970 Wan Zongshun
2016-07-11 22:14   ` Michael Turquette
2016-07-10  7:27 ` [PATCH v2 05/10] power/reset: Add reset driver support for nuc900 Wan Zongshun
2016-07-10 21:56   ` Paul Gortmaker
2016-07-11  2:30     ` Wan Zongshun
2016-07-11  2:58       ` Paul Gortmaker
2016-07-10  7:27 ` [PATCH v2 06/10] soc: Add SoC specific " Wan Zongshun
2016-07-11  8:03   ` Arnd Bergmann
2016-07-11  9:07     ` Wan Zongshun
2016-07-11 10:24       ` Arnd Bergmann
2016-07-11 10:28         ` Wan ZongShun
2016-07-11 10:36           ` Arnd Bergmann
2016-07-12  9:06     ` Wan Zongshun
2016-07-12  9:50       ` Arnd Bergmann
2016-07-10  7:27 ` [PATCH v2 07/10] ARM: dts: Add clock header file into dt-bindings Wan Zongshun

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