From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755101AbbBQM25 (ORCPT ); Tue, 17 Feb 2015 07:28:57 -0500 Received: from szxga03-in.huawei.com ([119.145.14.66]:35089 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754916AbbBQM2z (ORCPT ); Tue, 17 Feb 2015 07:28:55 -0500 Message-ID: <54E333CE.5010800@huawei.com> Date: Tue, 17 Feb 2015 20:27:58 +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> <54E314B3.40803@huawei.com> <20150217111104.5718d6f1@arm.com> In-Reply-To: <20150217111104.5718d6f1@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 X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020202.54E333D6.01A8,ss=1,re=0.001,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-05-26 15:14:31, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 601cc09dbac1225441dc3311fb8e646a Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2015/2/17 19:11, Marc Zyngier wrote: > On Tue, 17 Feb 2015 10:15:15 +0000 > "Yun Wu (Abel)" wrote: > >> 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); >> } > > That'd be a good start. But given that this is starting to be a common > construct, it could probably be rewritten as: > > static int its_poll_timeout(struct its_node *its, void *data, > int (*fn)(struct its_node *its, > void *data)) > { > while (1) { > if (!fn(its, data)) > return 0; > > ... > } > } > > and have the call sites to provide the right utility function. We also > have two similar timeout loops in the main GICv3 driver, so there > should be room for improvement. > > Thoughts? > It looks fine to me. I will make some improvement in the next version after Chinese Spring Festival. :) Thanks, Abel