[PATCH] usb: dwc2: gadget: initialize max_speed from params

[PATCH] usb: dwc2: gadget: initialize max_speed from params

[John Keeping]

DWC2 may be paired with a full-speed PHY which is not capable of
high-speed operation.  Report this correctly to the gadget core by
setting max_speed from the core parameters.

Prior to commit 5324bad66f09f ("usb: dwc2: gadget: implement
udc_set_speed()") this didn't cause the hardware to be configured
incorrectly, although the speed may have been reported incorrectly.  But
after that commit params.speed is updated based on a value passed in by
the gadget core which may set it to a faster speed than is supported by
the hardware.  Initialising the max_speed parameter ensures the speed
passed to dwc2_gadget_set_speed() will be one supported by the hardware.

Fixes: 5324bad66f09f ("usb: dwc2: gadget: implement udc_set_speed()")
Signed-off-by: John Keeping <john@metanate.com>
---
 drivers/usb/dwc2/gadget.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
index b884a83b26a6e..2bc03f41c70ad 100644
--- a/drivers/usb/dwc2/gadget.c
+++ b/drivers/usb/dwc2/gadget.c
@@ -4974,7 +4974,18 @@ int dwc2_gadget_init(struct dwc2_hsotg *hsotg)
 		hsotg->params.g_np_tx_fifo_size);
 	dev_dbg(dev, "RXFIFO size: %d\n", hsotg->params.g_rx_fifo_size);
 
-	hsotg->gadget.max_speed = USB_SPEED_HIGH;
+	switch (hsotg->params.speed) {
+	case DWC2_SPEED_PARAM_LOW:
+		hsotg->gadget.max_speed = USB_SPEED_LOW;
+		break;
+	case DWC2_SPEED_PARAM_FULL:
+		hsotg->gadget.max_speed = USB_SPEED_FULL;
+		break;
+	default:
+		hsotg->gadget.max_speed = USB_SPEED_HIGH;
+		break;
+	}
+
 	hsotg->gadget.ops = &dwc2_hsotg_gadget_ops;
 	hsotg->gadget.name = dev_name(dev);
 	hsotg->gadget.otg_caps = &hsotg->params.otg_caps;
-- 
2.34.1

Re: [PATCH] usb: dwc2: gadget: initialize max_speed from params

[Minas Harutyunyan]

Hi John,

On 12/2/2021 9:17 PM, John Keeping wrote:
> DWC2 may be paired with a full-speed PHY which is not capable of
> high-speed operation.  Report this correctly to the gadget core by
> setting max_speed from the core parameters.
> 
> Prior to commit 5324bad66f09f ("usb: dwc2: gadget: implement
> udc_set_speed()") this didn't cause the hardware to be configured
> incorrectly, although the speed may have been reported incorrectly.  But
> after that commit params.speed is updated based on a value passed in by
> the gadget core which may set it to a faster speed than is supported by
> the hardware.  Initialising the max_speed parameter ensures the speed
> passed to dwc2_gadget_set_speed() will be one supported by the hardware.
> 
> Fixes: 5324bad66f09f ("usb: dwc2: gadget: implement udc_set_speed()")
> Signed-off-by: John Keeping <john@metanate.com>
> ---
>   drivers/usb/dwc2/gadget.c | 13 ++++++++++++-
>   1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
> index b884a83b26a6e..2bc03f41c70ad 100644
> --- a/drivers/usb/dwc2/gadget.c
> +++ b/drivers/usb/dwc2/gadget.c
> @@ -4974,7 +4974,18 @@ int dwc2_gadget_init(struct dwc2_hsotg *hsotg)
>   		hsotg->params.g_np_tx_fifo_size);
>   	dev_dbg(dev, "RXFIFO size: %d\n", hsotg->params.g_rx_fifo_size);
>   
> -	hsotg->gadget.max_speed = USB_SPEED_HIGH;
> +	switch (hsotg->params.speed) {
> +	case DWC2_SPEED_PARAM_LOW:
> +		hsotg->gadget.max_speed = USB_SPEED_LOW;
> +		break;
> +	case DWC2_SPEED_PARAM_FULL:
> +		hsotg->gadget.max_speed = USB_SPEED_FULL;
> +		break;
> +	default:
> +		hsotg->gadget.max_speed = USB_SPEED_HIGH;
> +		break;
> +	}
> +
>   	hsotg->gadget.ops = &dwc2_hsotg_gadget_ops;
>   	hsotg->gadget.name = dev_name(dev);
>   	hsotg->gadget.otg_caps = &hsotg->params.otg_caps;
> 

Just setting gadget's max_speed doesn't resolve described issue. After 
setting gadget's max_speed in your patch, it doesn't used in driver at 
all. Per me, you need also fix dwc2_gadget_set_speed() function by 
checking requested speed with max_speed: if requested speed higher than 
max_speed then set speed to max_speed.

Thanks,
Minas

Re: [PATCH] usb: dwc2: gadget: initialize max_speed from params

[John Keeping]

Hi Minas,

On Fri, Dec 03, 2021 at 05:49:36AM +0000, Minas Harutyunyan wrote:
> On 12/2/2021 9:17 PM, John Keeping wrote:
> > DWC2 may be paired with a full-speed PHY which is not capable of
> > high-speed operation.  Report this correctly to the gadget core by
> > setting max_speed from the core parameters.
> > 
> > Prior to commit 5324bad66f09f ("usb: dwc2: gadget: implement
> > udc_set_speed()") this didn't cause the hardware to be configured
> > incorrectly, although the speed may have been reported incorrectly.  But
> > after that commit params.speed is updated based on a value passed in by
> > the gadget core which may set it to a faster speed than is supported by
> > the hardware.  Initialising the max_speed parameter ensures the speed
> > passed to dwc2_gadget_set_speed() will be one supported by the hardware.
> > 
> > Fixes: 5324bad66f09f ("usb: dwc2: gadget: implement udc_set_speed()")
> > Signed-off-by: John Keeping <john@metanate.com>
> > ---
> >   drivers/usb/dwc2/gadget.c | 13 ++++++++++++-
> >   1 file changed, 12 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
> > index b884a83b26a6e..2bc03f41c70ad 100644
> > --- a/drivers/usb/dwc2/gadget.c
> > +++ b/drivers/usb/dwc2/gadget.c
> > @@ -4974,7 +4974,18 @@ int dwc2_gadget_init(struct dwc2_hsotg *hsotg)
> >   		hsotg->params.g_np_tx_fifo_size);
> >   	dev_dbg(dev, "RXFIFO size: %d\n", hsotg->params.g_rx_fifo_size);
> >   
> > -	hsotg->gadget.max_speed = USB_SPEED_HIGH;
> > +	switch (hsotg->params.speed) {
> > +	case DWC2_SPEED_PARAM_LOW:
> > +		hsotg->gadget.max_speed = USB_SPEED_LOW;
> > +		break;
> > +	case DWC2_SPEED_PARAM_FULL:
> > +		hsotg->gadget.max_speed = USB_SPEED_FULL;
> > +		break;
> > +	default:
> > +		hsotg->gadget.max_speed = USB_SPEED_HIGH;
> > +		break;
> > +	}
> > +
> >   	hsotg->gadget.ops = &dwc2_hsotg_gadget_ops;
> >   	hsotg->gadget.name = dev_name(dev);
> >   	hsotg->gadget.otg_caps = &hsotg->params.otg_caps;
> > 
> 
> Just setting gadget's max_speed doesn't resolve described issue. After 
> setting gadget's max_speed in your patch, it doesn't used in driver at 
> all. Per me, you need also fix dwc2_gadget_set_speed() function by 
> checking requested speed with max_speed: if requested speed higher than 
> max_speed then set speed to max_speed.

Setting the max_speed here restricts what the gadget core will pass in
to the .udc_set_speed hook, see usb_gadget_udc_set_speed():

	s = min(speed, udc->gadget->max_speed);
	udc->gadget->ops->udc_set_speed(udc->gadget, s);

We can't add a check in dwc2_gadget_set_speed() because the original
capability may have been lost, for example if a high-speed capable
device is configured for full-speed operation then hsotg->params.speed
is set to full-speed and there's nothing that says the device is capable
of high-speed when setting the speed back again.

I believe this patch is sufficient because of the guarantees by the
gadget core that we will never be called with a speed that is faster
than we support.


Regards,
John

Re: [PATCH] usb: dwc2: gadget: initialize max_speed from params

[Minas Harutyunyan]

On 12/3/2021 3:36 PM, John Keeping wrote:
> Hi Minas,
> 
> On Fri, Dec 03, 2021 at 05:49:36AM +0000, Minas Harutyunyan wrote:
>> On 12/2/2021 9:17 PM, John Keeping wrote:
>>> DWC2 may be paired with a full-speed PHY which is not capable of
>>> high-speed operation.  Report this correctly to the gadget core by
>>> setting max_speed from the core parameters.
>>>
>>> Prior to commit 5324bad66f09f ("usb: dwc2: gadget: implement
>>> udc_set_speed()") this didn't cause the hardware to be configured
>>> incorrectly, although the speed may have been reported incorrectly.  But
>>> after that commit params.speed is updated based on a value passed in by
>>> the gadget core which may set it to a faster speed than is supported by
>>> the hardware.  Initialising the max_speed parameter ensures the speed
>>> passed to dwc2_gadget_set_speed() will be one supported by the hardware.
>>>
>>> Fixes: 5324bad66f09f ("usb: dwc2: gadget: implement udc_set_speed()")
>>> Signed-off-by: John Keeping <john@metanate.com>

Acked-by: Minas Harutyunyan <Minas.Harutyunyan@synopsys.com>

>>> ---
>>>    drivers/usb/dwc2/gadget.c | 13 ++++++++++++-
>>>    1 file changed, 12 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
>>> index b884a83b26a6e..2bc03f41c70ad 100644
>>> --- a/drivers/usb/dwc2/gadget.c
>>> +++ b/drivers/usb/dwc2/gadget.c
>>> @@ -4974,7 +4974,18 @@ int dwc2_gadget_init(struct dwc2_hsotg *hsotg)
>>>    		hsotg->params.g_np_tx_fifo_size);
>>>    	dev_dbg(dev, "RXFIFO size: %d\n", hsotg->params.g_rx_fifo_size);
>>>    
>>> -	hsotg->gadget.max_speed = USB_SPEED_HIGH;
>>> +	switch (hsotg->params.speed) {
>>> +	case DWC2_SPEED_PARAM_LOW:
>>> +		hsotg->gadget.max_speed = USB_SPEED_LOW;
>>> +		break;
>>> +	case DWC2_SPEED_PARAM_FULL:
>>> +		hsotg->gadget.max_speed = USB_SPEED_FULL;
>>> +		break;
>>> +	default:
>>> +		hsotg->gadget.max_speed = USB_SPEED_HIGH;
>>> +		break;
>>> +	}
>>> +
>>>    	hsotg->gadget.ops = &dwc2_hsotg_gadget_ops;
>>>    	hsotg->gadget.name = dev_name(dev);
>>>    	hsotg->gadget.otg_caps = &hsotg->params.otg_caps;
>>>
>>
>> Just setting gadget's max_speed doesn't resolve described issue. After
>> setting gadget's max_speed in your patch, it doesn't used in driver at
>> all. Per me, you need also fix dwc2_gadget_set_speed() function by
>> checking requested speed with max_speed: if requested speed higher than
>> max_speed then set speed to max_speed.
> 
> Setting the max_speed here restricts what the gadget core will pass in
> to the .udc_set_speed hook, see usb_gadget_udc_set_speed():
> 
> 	s = min(speed, udc->gadget->max_speed);
> 	udc->gadget->ops->udc_set_speed(udc->gadget, s);
> 
> We can't add a check in dwc2_gadget_set_speed() because the original
> capability may have been lost, for example if a high-speed capable
> device is configured for full-speed operation then hsotg->params.speed
> is set to full-speed and there's nothing that says the device is capable
> of high-speed when setting the speed back again.
> 
> I believe this patch is sufficient because of the guarantees by the
> gadget core that we will never be called with a speed that is faster
> than we support.
> 
> 
> Regards,
> John
>