Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933626AbbBQKQN (ORCPT ); Tue, 17 Feb 2015 05:16:13 -0500 Received: from szxga02-in.huawei.com ([119.145.14.65]:14572 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933320AbbBQKQL (ORCPT ); Tue, 17 Feb 2015 05:16:11 -0500 Message-ID: <54E314B3.40803@huawei.com> Date: Tue, 17 Feb 2015 18:15:15 +0800 From: "Yun Wu (Abel)" User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:11.0) Gecko/20120327 Thunderbird/11.0.1 MIME-Version: 1.0 To: Marc Zyngier CC: "tglx@linutronix.de" , "jason@lakedaemon.net" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v2 5/6] irqchip: gicv3-its: add support for power down References: <1423992723-5028-1-git-send-email-wuyun.wu@huawei.com> <1423992723-5028-6-git-send-email-wuyun.wu@huawei.com> <20150217092935.1fefcb24@arm.com> In-Reply-To: <20150217092935.1fefcb24@arm.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.24.136] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2245 Lines: 78 On 2015/2/17 17:29, Marc Zyngier wrote: > On Sun, 15 Feb 2015 09:32:02 +0000 > Yun Wu wrote: > >> It's unsafe to change the configurations of an activated ITS directly >> since this will lead to unpredictable results. This patch guarantees >> a safe quiescent status before initializing an ITS. > > Please change the title of this patch to reflect what it actually > does. Nothing here is about powering down anything. My miss, I will fix this in next version. > >> Signed-off-by: Yun Wu >> --- >> drivers/irqchip/irq-gic-v3-its.c | 32 >> ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) >> >> diff --git a/drivers/irqchip/irq-gic-v3-its.c >> b/drivers/irqchip/irq-gic-v3-its.c index 42c03b2..29eb665 100644 >> --- a/drivers/irqchip/irq-gic-v3-its.c >> +++ b/drivers/irqchip/irq-gic-v3-its.c >> @@ -1321,6 +1321,31 @@ static const struct irq_domain_ops >> its_domain_ops = { .deactivate = >> its_irq_domain_deactivate, }; >> >> +static int its_check_quiesced(void __iomem *base) >> +{ >> + u32 count = 1000000; /* 1s */ >> + u32 val; >> + >> + val = readl_relaxed(base + GITS_CTLR); >> + if (val & GITS_CTLR_QUIESCENT) >> + return 0; >> + >> + /* Disable the generation of all interrupts to this ITS */ >> + val &= ~GITS_CTLR_ENABLE; >> + writel_relaxed(val, base + GITS_CTLR); >> + >> + /* Poll GITS_CTLR and wait until ITS becomes quiescent */ >> + while (count--) { >> + val = readl_relaxed(base + GITS_CTLR); >> + if (val & GITS_CTLR_QUIESCENT) >> + return 0; >> + cpu_relax(); >> + udelay(1); >> + } > > You're now introducing a third variant of a 1s timeout loop. Notice a > pattern? > I am not sure I know exactly what you suggest. Do you mean I should code like below to keep the coding style same as the other 2 loops? while (1) { val = readl_relaxed(base + GITS_CTLR); if (val & GITS_CTLR_QUIESCENT) return 0; count--; if (!count) return -EBUSY; cpu_relax(); udelay(1); } Thanks, Abel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/