linux-kernel - Re: [PATCH v2 0/3] usb: musb: da8xx: Fix few issues

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Date:   Fri, 28 Oct 2016 11:31:35 +0200
From:   Alexandre Bailon <abailon@...libre.com>
To:     David Lechner <david@...hnology.com>, khilman@...libre.com,
        b-liu@...com, balbi@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v2 0/3] usb: musb: da8xx: Fix few issues

On 10/27/2016 08:44 PM, David Lechner wrote:
> On 10/27/2016 12:16 PM, David Lechner wrote:
>> On 10/26/2016 05:58 AM, Alexandre Bailon wrote:
>>> Currently, the USB OTG of the da8xx doesn't work.
>>> This series intend to fix them.
>>>
>>> Change in v2:
>>> * Fix the error path da8xx_musb_init()
>>>
>>> Alexandre Bailon (3):
>>>   usb: musb: da8xx: Call earlier clk_prepare_enable()
>>>   phy: da8xx-usb: Configure CFGCHIP2 to support OTG workaround
>>>   usb: musb: da8xx: Only execute the OTG workaround when phy in OTG mode
>>>
>>>  drivers/phy/phy-da8xx-usb.c | 17 ++++++++++++-----
>>>  drivers/usb/musb/da8xx.c    | 28 +++++++++++++++++++---------
>>>  2 files changed, 31 insertions(+), 14 deletions(-)
>>>
>>
>> I have found another problem with peripheral mode. When we force
>> peripheral mode, the glue layer currently uses CFGCHIP2 to override the
>> VBUS and ID. This causes it to not be able to detect disconnection
>> because the VBUS is overridden.
How have you found it ? Does it cause any issues ?
I mean I had to enable traces to see that disconnect was not happening.
>>
>> Here is a patch to fix the problem. I have tested this on LEGO
>> MINDSTORMS EV3 (AM1808). This works because the ID pin is internally
>> pulled up on the SoC, so we don't need to override it.
Actually, I'm wonder if that if not related to VBUS sensing.
May be we should set CFGCHIP2_VBDTCTEN in device mode.
>>
>> ---
>>
>> diff --git a/drivers/usb/musb/da8xx.c b/drivers/usb/musb/da8xx.c
>> index 2bc12a2..33daa3b 100644
>> --- a/drivers/usb/musb/da8xx.c
>> +++ b/drivers/usb/musb/da8xx.c
>> @@ -374,9 +374,7 @@ static int da8xx_musb_set_mode(struct musb *musb, u8
>> musb_mode)
>>         case MUSB_HOST:         /* Force VBUS valid, ID = 0 */
>>                 phy_mode = PHY_MODE_USB_HOST;
>>                 break;
>> -       case MUSB_PERIPHERAL:   /* Force VBUS valid, ID = 1 */
>> -               phy_mode = PHY_MODE_USB_DEVICE;
>> -               break;
>> +       case MUSB_PERIPHERAL:
>>         case MUSB_OTG:          /* Don't override the VBUS/ID
>> comparators */
>>                 phy_mode = PHY_MODE_USB_OTG;
>>                 break;
>>
>> ---
>>
>> If this works for other SoCs/boards, I think we should make this change.
>> If it doesn't work, we could work around the VBUS problem by polling
>> VBUSSENSE in CFGCHIP2. But, I like the simple solution above better.
> 
> I have realized that due to the way my device is wired, I can actually
> use OTG mode and it will behave exactly as peripheral mode because the
> ID pin is not connected. So, maybe this patch is not needed after all.
> 
Actually, I'm sure that is related to ID
I have the same issue except the disconnect is called when I use the
OTG mode.