linux-kernel - why we need a msleep(5) in ehci_bus

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Message-ID: <CAGALBbCEvz5-j6vs=y7AJHZB82HeG+VRbg++yL9xj2gpaW+2Lw@mail.gmail.com>
Date:	Mon, 13 May 2013 14:17:20 +0800
From:	linux fddl <fddllinux@...il.com>
To:	stern@...land.harvard.edu, linux-usb@...r.kernel.org,
	gregkh@...e.de
Cc:	linux-kernel@...r.kernel.org
Subject: why we need a msleep(5) in ehci_bus_suspend/resume

Hi,

  From the ehci-hub.c, I find that ehci_bus_suspend/resume have some
code like this:

if (time_before(jiffies, ehci->netx_statechange))
    msleep(5);
...
ehci->next_statechange = jiffies + msec_to_jiffies(10);

and

if (time_before(jiffies, ehci->netx_statechange))
    msleep(5);
...
ehci->next_statechange = jiffies + msec_to_jiffies(5);

but I don't know why such a short sleep is needed, and why one is
[ehci->next_statechange = jiffies + msec_to_jiffies(10)] and the other is
[ehci->next_statechange = jiffies + msec_to_jiffies(5)],
I googled for a long time, but it seems that there is no explanation.

  Anyone knows why and can give any explanation?

  Thanks very much!

Best Regards!
ShiJinghui
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