[Letux-kernel] musb otg/y-cable regressions, OTG support removal

Wed Feb 20 11:53:00 CET 2019

Hi Andreas,

> Am 19.02.2019 um 21:14 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> 
> 
>> Am 19.02.2019 um 20:33 schrieb Andreas Kemnade <andreas at kemnade.info>:
>> 
>> On Mon, 18 Feb 2019 09:07:27 +0100
>> "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
>> 
>>> Hi,
>>> 
>>>> Am 18.02.2019 um 07:58 schrieb Andreas Kemnade <andreas at kemnade.info>:
>>>> 
>>>> Hi,
>>>> 
>>>> after quite some searching why b_host mode only works very randomly, I found
>>>> out that
>>>> - musb: disable b_host wait timeout for y-cable usage
>>>> is missing in >= letux-4.18. Seems to be forgotten in a conflict resolution.  
>>> 
>>> I have checked and it did no longer apply. So yes, it was probably forgotten
>>> to convert into a correct fix.
>>> 
>>> This one appears to apply:
>>> 
>>> commit 1a27badcf1ce03cb8bc69bdb72d76fd27660cf49 (HEAD -> letux/musb-fixes)
>>> Author: Andreas Kemnade <andreas at kemnade.info>
>>> Date:   Mon Feb 13 17:16:57 2017 +0100
>>> 
>>>   musb: disable b_host wait timeout for y-cable usage
>>> 
>>>   To be able to use Y-cables to power the device and use it as host at
>>>   the same time, disable the b_waitacon timeout.
>>> 
>>>   Signed-off-by: Andreas Kemnade <andreas at kemnade.info>
>>> 
>>> diff --git a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c
>>> index b7d56272f9d1..780787540b85 100644
>>> --- a/drivers/usb/musb/musb_core.c
>>> +++ b/drivers/usb/musb/musb_core.c
>>> @@ -718,9 +718,15 @@ static void musb_handle_intr_suspend(struct musb *musb, u8 devctl)
>>>               if (musb->is_active) {
>>>                       musb->xceiv->otg->state = OTG_STATE_B_WAIT_ACON;
>>>                       musb_dbg(musb, "HNP: Setting timer for b_ase0_brst");
>>> +               /* If trying to switch to b_host without a real
>>> +                * hnp reset (y-cables and such) the timer might
>>> +                * be disturbing
>>> +                */
>>> +#if 0
>>>                       mod_timer(&musb->otg_timer, jiffies
>>>                               + msecs_to_jiffies(
>>>                                               OTG_TIME_B_ASE0_BRST));
>>> +#endif
>>>               }
>>>               break;
>>>       case OTG_STATE_A_WAIT_BCON:
>>> 
>>> 
>>>> - and them we have this one
>>>> commit 0a9134bd733bbb99bd18f5520a488960170271f2
>>>> Author: Bin Liu <b-liu at ti.com>
>>>> Date:   Mon May 21 08:42:19 2018 -0500
>>>> 
>>>>  usb: musb: disable otg protocol support
>>>> 
>>>>  As decided in the discussion [1] we are deleting the otg protocol
>>>>  support from the musb drivers.
>>>> 
>>>>  First this patch disables the flags for enabling the otg protocols. We
>>>>  will later gradually delete the otg protocol code from the musb drivers.
>>>> 
>>>>  [1] https://www.spinics.net/lists/linux-usb/msg167003.html
>>>> 
>>>>  Signed-off-by: Bin Liu <b-liu at ti.com>
>>>>  Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
>>>> 
>>>> that seems also to influence things.

It appears to have been introduced in v4.18-rc2.

>>>> 
>> 
>> ok, played a bit around with it. Reverting it enables me to do
>> all the things I do with that otg usb.
> 
> I have included the above patch in 5.0-rc7 and scheduled for
> the next 4.19/4.20 (forgot to include it immediately).
> 
> Regarding USB/OTG I want to do some tests myself. Then we should
> raise fingers and submit the revert...

I have done a simple test: plug in the OTG cable and then plug a memory stick or WiFi stick:

root at letux:~# [  452.581024] musb-hdrc musb-hdrc.0.auto: configured as A device timeout

root at letux:~# [  461.739410] usb 2-1: new high-speed USB device number 2 using musb-hdrc
[  461.920166] usb 2-1: New USB device found, idVendor=0204, idProduct=6025, bcdDevice= 1.00
[  461.928833] usb 2-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[  461.937591] usb 2-1: Product: Flash Disk
[  461.942596] usb 2-1: Manufacturer: CBM
[  461.946594] usb 2-1: SerialNumber: 221835001DC5F204
[  461.960357] usb-storage 2-1:1.0: USB Mass Storage device detected
[  461.985290] scsi host0: usb-storage 2-1:1.0
[  463.070312] scsi 0:0:0:0: Direct-Access     CBM      Flash Disk       5.00 PQ: 0 ANSI: 2
[  463.091278] sd 0:0:0:0: [sda] 2072064 512-byte logical blocks: (1.06 GB/1012 MiB)
[  463.104431] sd 0:0:0:0: Attached scsi generic sg0 type 0
[  463.111389] sd 0:0:0:0: [sda] Write Protect is off
[  463.116394] sd 0:0:0:0: [sda] Mode Sense: 0b 00 00 08
[  463.129638] sd 0:0:0:0: [sda] No Caching mode page found
[  463.135223] sd 0:0:0:0: [sda] Assuming drive cache: write through
[  463.160888]  sda: sda1
[  463.167755] sd 0:0:0:0: [sda] Attached SCSI removable disk
[  469.191070] usb 2-1: USB disconnect, device number 2
[  488.261047] usb 2-1: new high-speed USB device number 3 using musb-hdrc
[  488.441894] usb 2-1: New USB device found, idVendor=0204, idProduct=6025, bcdDevice= 1.00
[  488.450683] usb 2-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[  488.458251] usb 2-1: Product: Flash Disk
[  488.463684] usb 2-1: Manufacturer: CBM
[  488.467681] usb 2-1: SerialNumber: 221835001DC5F204
[  488.481872] usb-storage 2-1:1.0: USB Mass Storage device detected
[  488.503936] scsi host0: usb-storage 2-1:1.0
[  489.552581] scsi 0:0:0:0: Direct-Access     CBM      Flash Disk       5.00 PQ: 0 ANSI: 2
[  489.568054] sd 0:0:0:0: [sda] 2072064 512-byte logical blocks: (1.06 GB/1012 MiB)
[  489.582794] sd 0:0:0:0: Attached scsi generic sg0 type 0
[  489.593719] sd 0:0:0:0: [sda] Write Protect is off
[  489.598754] sd 0:0:0:0: [sda] Mode Sense: 0b 00 00 08
[  489.615386] sd 0:0:0:0: [sda] No Caching mode page found
[  489.621124] sd 0:0:0:0: [sda] Assuming drive cache: write through
[  489.633056]  sda: sda1
[  489.643096] sd 0:0:0:0: [sda] Attached SCSI removable disk
[  492.219909] usb 2-1: USB disconnect, device number 3
[  501.991546] usb 2-1: new high-speed USB device number 4 using musb-hdrc
[  502.182739] usb 2-1: New USB device found, idVendor=0bda, idProduct=8179, bcdDevice= 0.00
[  502.191528] usb 2-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[  502.199096] usb 2-1: Product: 802.11n NIC
[  502.205078] usb 2-1: Manufacturer: Realtek
[  502.209533] usb 2-1: SerialNumber: 7CDD90A871B2
[  502.221984] usb 2-1: rejected 1 configuration due to insufficient available bus power
[  502.230285] usb 2-1: no configuration chosen from 1 choice
[  509.010009] usb 2-1: USB disconnect, device number 4

Both seem to work (at least to available bus power).

This means that basic OTG (role switch by ID pin) is still working with letux-4.19.23.

So could a different solution for the Y cable be to fake an active ID pin?

BR,
Nikolaus