From: Yijing Wang <wangyijing@huawei.com>
To: Bjorn Helgaas <bhelgaas@google.com>
Cc: <linux-pci@vger.kernel.org>
Subject: Re: [PATCH 3/3] PCI: Use usleep_range() instead of msleep() for better accuracy
Date: Wed, 24 Jun 2015 09:47:11 +0800 [thread overview]
Message-ID: <558A0C1F.6010405@huawei.com> (raw)
In-Reply-To: <20150619171249.GK7710@google.com>
On 2015/6/20 1:12, Bjorn Helgaas wrote:
> On Fri, Jun 19, 2015 at 03:57:46PM +0800, Yijing Wang wrote:
>> Msleep < 20ms can sleep for up to 20ms, see
>> Documentation/timers/timers-howto.txt, so we could
>> use usleep_range instead.
>>
>> Signed-off-by: Yijing Wang <wangyijing@huawei.com>
>> ---
>> drivers/pci/hotplug/pciehp_hpc.c | 2 +-
>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
>> index daf54be..4553728 100644
>> --- a/drivers/pci/hotplug/pciehp_hpc.c
>> +++ b/drivers/pci/hotplug/pciehp_hpc.c
>> @@ -118,7 +118,7 @@ static int pcie_poll_cmd(struct controller *ctrl, int timeout)
>> }
>> if (timeout < 0)
>> break;
>> - msleep(10);
>> + usleep_range(10000, 11000);
>
> timers-howto.txt also says to use msleep for 10ms+ delays, so the guidance
> is a bit ambiguous.
>
> This particular delay does not need to be precise, and if we delay 20ms
> instead of 10ms (1/50th of a second vs 1/100th of a second), I don't think
> it makes any difference at all.
>
> If we *did* make a change here, I think we should use a range of at least
> 10ms. There's no need to tighten the wakeup time to the 1ms window between
> 10ms and 11ms. Any time in the range of 10ms to 50ms would probably be
> fine.
>
> But I don't think a change here is necessary, and it does make it a bit
> harder to analyze the code because we have some things in microseconds and
> others in milliseconds.
OK, I got it, thanks for your explanation.
Thanks!
Yijing.
>
>> timeout -= 10;
>> }
>> return 0; /* timeout */
>> --
>> 1.7.1
>>
>
>
--
Thanks!
Yijing
next prev parent reply other threads:[~2015-06-24 1:47 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-19 7:57 [PATCH 0/3] Trivial pci hotplug changes Yijing Wang
2015-06-19 7:57 ` [PATCH 1/3] PCI: Use "slot" and "pci_slot" for struct hotplug_slot and struct pci_slot Yijing Wang
2015-06-19 7:57 ` [PATCH 2/3] PCI: Simplify pcie_poll_cmd() Yijing Wang
2015-06-19 7:57 ` [PATCH 3/3] PCI: Use usleep_range() instead of msleep() for better accuracy Yijing Wang
2015-06-19 17:12 ` Bjorn Helgaas
2015-06-24 1:47 ` Yijing Wang [this message]
2015-06-19 17:14 ` [PATCH 0/3] Trivial pci hotplug changes Bjorn Helgaas
2015-06-24 1:47 ` Yijing Wang
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