linux-kernel - Re: [PATCH] usb: musb: dsps: handle the otg_state_a_wait_vrise

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Message-ID: <5666EC67.7000203@ti.com>
Date:	Tue, 8 Dec 2015 08:42:47 -0600
From:	Bin Liu <b-liu@...com>
To:	Felipe Balbi <balbi@...com>,
	Gregory CLEMENT <gregory.clement@...e-electrons.com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <stable@...r.kernel.org>
Subject: Re: [PATCH] usb: musb: dsps: handle the
 otg_state_a_wait_vrise_timeout case



On 12/08/2015 08:35 AM, Felipe Balbi wrote:
>
> Hi,
>
> Bin Liu <b-liu@...com> writes:
>> Felipe,
>>
>> On 12/08/2015 08:20 AM, Felipe Balbi wrote:
>>>
>>> Hi,
>>>
>>> Gregory CLEMENT <gregory.clement@...e-electrons.com> writes:
>>>>>>> if it is the case then it didn't fix the issue I had.
>>>>>>>
>>>>>>> I activated the following debug line:
>>>>>>>
>>>>>>> [musb_hdrc]musb_interrupt =_ "** IRQ %s usb%04x tx%04x rx%04x\012"
>>>>>>> [musb_dsps]dsps_interrupt =p "usbintr (%x) epintr(%x)\012"
>>>>>>>
>>>>>>> But I didn't get any interrupt while disconnecting the cable without any
>>>>>>> device connected on it (whereas I got an interrupt when I connected it).
>>>>>>>
>>>>>>> Note that I applied this patch instead of the "usb: musb: dsps: handle
>>>>>>> the otg_state_a_wait_vrise_timeout case", is what you had in mind ?
>>>>>
>>>>> yeah, that's what I had in mind. But your patch seems wrong :-)
>>>>>
>>>>> I tried writing a more correct version here and found 2 issues:
>>>>>
>>>>> a) bit 3 doesn't do anything :-p I cannot read IRQs from mentor's
>>>>> registers
>>>>>
>>>>> b) when setting RESET_ISOLATION bit, reads of CTRL register hang. Note
>>>>> that according to TRM, RESET_ISOLATION _must_ be set prior to a soft
>>>>> reset and cleared afterwards. But right after setting RESET_ISOLATION,
>>>>> if I try a read of CTRL, it'll hang forever.
>>>>
>>>> The datasheet seems not very coherent about it,
>>>>
>>>> on one side we have:
>>>> "This bit should be set high prior to setting bit 0 and cleared after bit 0
>>>> is cleared."
>>>>
>>>> and on the other side:
>>>> "Both the soft_reset and soft_reset_isolation bits should be asserted
>>>> simultaneously."
>>>>
>>>> The hang you saw could be explained by the following:
>>>> "Setting only the soft_reset_isolation bit will cause all USB0 output
>>>> signals to go to a known constant value via multiplexers.
>>>> This will
>>>> prevent future access to USB0."  page 2567
>>>
>>> good catch. Setting them together makes the hang go away.
>>>
>>> I still have the other problem, which is legacy IRQ reporting mode not
>>> really working.
>>>
>>
>> I never tried to change the IRQ mapping. The 8 MUSB interrupt will be
>> the same no matter where they are reported from. What do you expect when
>> switch to the MUSB IRQ reporting mode?
>
> read events from MUSB's registers instead of TI's :-) so, MUSB_INTRUSB,
> MUSB_INTRRX and MUSB_INTRTX.
>
I meant you expect to see any different event when switch to MUSB IRQ 
mode? The TI wrapper just reports the same 8 interrupt events. I don't 
think you would get any difference.

BTY, I think I miss some context here. This Gregory's patch is trying to 
fix the OTG state machine problem in musb_dsps, which is replicated with 
a cable without a device connected. But it also mentions about 
non-compliant MSC devices. How are the thumb drives related to this OTG 
state issue?

-- 
Regards,
-Bin.
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