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

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Message-ID: <245c574f-912a-9997-094e-069211dd2c2e@lechnology.com>
Date:   Thu, 27 Oct 2016 13:44:52 -0500
From:   David Lechner <david@...hnology.com>
To:     Alexandre Bailon <abailon@...libre.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 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.
>
> 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.
>
> ---
>
> 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.