2016-07-15 15:00 GMT+08:00 Arnd Bergmann <arnd@xxxxxxxx>: > 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 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html