linux-kernel - Re: [PATCH] usb: dwc3: gadget: Fix .udc_set

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Message-ID: <c0794b4c-6f86-e852-2670-78c8271c3fef@ti.com>
Date:   Tue, 31 Oct 2017 15:27:34 +0200
From:   Roger Quadros <rogerq@...com>
To:     Felipe Balbi <balbi@...nel.org>
CC:     <Dylan.Howey@...nantco.com>, <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        "# v4 . 13+" <stable@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: gadget: Fix .udc_set_speed()


Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

On 31/10/17 15:24, Felipe Balbi wrote:
> Roger Quadros <rogerq@...com> writes:
> 
>> UDC core calls .udc_set_speed() with the speed parameter
>> containing the maximum speed supported by the gadget function
>> driver. This might very well be more or less than that
>> supported by the dwc3 controller driver.
>>
>> Select the lesser of the 2 speeds so both are operating
>> within limits.
>>
>> This fixes PHY Erratic errors and 2 second enumeration delay on
>> TI's AM437x platforms.
>>
>> Fixes: 7d8d0639565f ("usb: dwc3: gadget: implement ->udc_set_speed()")
>> Cc: <stable@...r.kernel.org> # v4.13+
>> Reported-by: Dylan Howey <Dylan.Howey@...nantco.com>
>> Signed-off-by: Roger Quadros <rogerq@...com>
>> ---
>>  drivers/usb/dwc3/gadget.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index f064f15..9f27ec0 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -2008,6 +2008,8 @@ static void dwc3_gadget_set_speed(struct usb_gadget *g,
>>  	unsigned long		flags;
>>  	u32			reg;
>>  
>> +	speed = min(g->max_speed, speed);
> 
> should we do that in udc core itself?
> 
> @@ -1080,8 +1080,12 @@ static inline void usb_gadget_udc_stop(struct usb_udc *udc)
>  static inline void usb_gadget_udc_set_speed(struct usb_udc *udc,
>  					    enum usb_device_speed speed)
>  {
> -	if (udc->gadget->ops->udc_set_speed)
> -		udc->gadget->ops->udc_set_speed(udc->gadget, speed);
> +	if (udc->gadget->ops->udc_set_speed) {
> +		enum usb_device_speed s;
> +
> +		s = min(speed, udc->gadget->max_speed);
> +		udc->gadget->ops->udc_set_speed(udc->gadget, s);
> +	}
>  }
>  
>  /**
> 
> then the fix applies for all UDCs.
> 

Sounds like a good idea. Will re-spin this patch.

-- 
cheers,
-roger

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki