From: Lars Melin <larsm17@gmail.com>
To: JH <jupiter.hce@gmail.com>, Greg KH <gregkh@linuxfoundation.org>
Cc: linux-usb@vger.kernel.org
Subject: Re: Failed to connect to 4G modem
Date: Wed, 18 Sep 2019 08:43:43 +0700 [thread overview]
Message-ID: <42e92dcb-0165-7a64-1391-c8ff602878a1@gmail.com> (raw)
In-Reply-To: <CAA=hcWTD2zYD0gVTu6sDuRqUcTOnn42Gm0s1tOGvBQdQ40Q7LA@mail.gmail.com>
On 9/18/2019 04:38, JH wrote:
......
>
> That was always my thought until I tried kernel 5.1 under the same
> platform (nothing changed except the kernel version), the kernel 5.1
> can connect to the 4G modem, I could not tell the hardware engineer if
> it was hardware problem where kernel 5.1 can connect, kernel 4.19
> could not, how would you explain it? Seems some differences between
> kernel 5.1 and kernel 4.19, what I could be missing?
Tell your hardware engineer to log the VBUS supply together with the
current consumption of the 4G card.
A glitch in the VBUS supply, often caused by an increase in current
consumption is a common reason for a usb modem to reset and temporarily
fall off the usb bus.
br
Lars
next prev parent reply other threads:[~2019-09-18 1:43 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-17 11:29 Failed to connect to 4G modem JH
2019-09-17 12:02 ` Greg KH
2019-09-17 21:38 ` JH
2019-09-18 1:43 ` Lars Melin [this message]
2019-09-18 5:47 ` Greg KH
2019-09-19 7:37 ` Bjørn Mork
2019-09-19 11:17 ` JH
2019-09-20 22:10 ` JH
2019-09-21 4:45 ` Greg KH
2019-09-22 22:17 ` JH
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