From mboxrd@z Thu Jan 1 00:00:00 1970 From: wuyun.wu@huawei.com (Yun Wu (Abel)) Date: Wed, 4 Mar 2015 11:10:55 +0800 Subject: [PATCH v2 5/6] irqchip: gicv3-its: add support for power down In-Reply-To: <54E333CE.5010800@huawei.com> 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> <54E333CE.5010800@huawei.com> Message-ID: <54F677BF.9060208@huawei.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 2015/2/17 20:27, Yun Wu (Abel) wrote: > 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? >> Hi Marc, Currently I didn't make any improvement on providing a unified utility function to do the timeout loops, because I haven't found a proper way yet. And to achieve this, at least three aspects I can imagine are needed to be considered. Refactoring the existing loop functions comes first. A prototype is showed below. static T1 func_prototype(T2 node, char *msg, void **args) { u32 count = 1000000; do_something_here(node, args); while (1) { if (condition_satisfied(node, args)) return (T1)SUCCESS; count--; if (!count) { print_err_msg(msg); return (T1)FAIL; } cpu_relax(); udelay(1); } } Obviously it will make things complicated to move do_something_here() and print_err_msg() outside of func_prototype(), because func_prototype() could be called sereval places. But the two functions are different from each loop function, so... static T1 func_prototype(T2 node, char *msg, void **args) { u32 count = 1000000; do_something_here(node, args); while (count--) { if (condition_satisfied(node, args)) return (T1)SUCCESS; cpu_relax(); udelay(1); } print_err_msg(msg); return (T1)FAIL; } Now we can unify the loop part, static bool condition_satisfied(T2 node, void **args); static u32 poll_timeout(T2 node, void **args, bool (*fn)(T2, void **)) { u32 count = 1000000; while (count--) { if (fn(node, args)) break; cpu_relax(); udelay(1); } return count; } static T1 func_prototype(T2 node, char *msg, void **args) { do_something_here(node, args); if (poll_timeout(node, args, condition_satisfied)) { return (T1)SUCCESS; } else { print_err_msg(msg); return (T1)FAIL; } } Look at what I have done, turn the original N loop functions to 2*N+1 functions. It can hardly be called improvement.. :( The 2nd and 3rd aspects are return value and list of parameters respectively. Using (void *) may help a lot, I think. Thoughts? Thanks, Abel