linux-kernel - Re: [PATCH 14/16] usb: musb: dsps: add MUSB_DEVCTL

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CADYTM3bfkxEYgvk5v_0=BJFMb8izULpgc1uZVPDPnSs29UpYeA@mail.gmail.com>
Date:	Fri, 26 Jul 2013 12:53:25 -0500
From:	Bin Liu <binmlist@...il.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	balbi@...com, george.cherian@...com
Subject: Re: [PATCH 14/16] usb: musb: dsps: add MUSB_DEVCTL_SESSION back after removal

Sebastian,

On Fri, Jul 26, 2013 at 11:31 AM, Sebastian Andrzej Siewior
<bigeasy@...utronix.de> wrote:
> * Bin Liu | 2013-07-23 13:55:27 [-0500]:
>
>>Hi Sebastian,
> Hi Bin,
>
>>either by SRP or HNP, or something else. In TI 3.2 kernel, there is
>>workaround in otg_timer() to _toggle_ the SESSION bit to detect if ID
>>pin is grounded, which means a USB device is connected.
>
> I've been looking at
>   http://downloads.ti.com/sitara_linux/esd/AM335xSDK/latest/index_FDS.html
>
> and I can't find what you are talking about. My MUSB_DEVCTL doesn't
> change after I connect a device and the SESSION bit is not set. Also I
> remain in a_idle state. Do you have maybe a hint for me? :)

In TI 3.2 kernel, the otg_timer() toggles the SESSION bit in
OTG_STATE_B_IDLE state. So whenever the ID pin is grounded by
connecting a device, the controller will try go into host mode.
But I have no idea why your board is in a_idle not b_idle. The toggle
does not handle a_idle.

Do you use the AM335x GP EVM, not the smaller StarterKit EVM, right?
the USB0 port on SK EVM is device only.

But anyway, I have not seen any use case which uses micro-AB
receptacle and requires such dynamic role switching. So I kind of
think it is unnecessary to implement this feature.

And it is not easy to implement it in a right way, because AM335x does
not have an interrupt for ID pin grounding, so we can only try to set
SESSION bit in otg_timer(), but that causes 2sec VBUS pulsing on the
wire, which violates the specs.

>
>>Regards,
>>-Bin.
>
> Sebastian
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/