Re: [PATCH v2] usb: cdns3: gadget: Fix g_audio use case when connected to Super-Speed host

Roger Quadros
2019-10-31T10:35:41Z

Hi,

On 31/10/2019 10:55, Felipe Balbi wrote:
>
> Hi,
>
> Roger Quadros <rogerq@ti.com> writes:
>
>> Take into account gadget driver's speed limit when programming
>> controller speed.
>>
>> Fixes: commit 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver")
>> Signed-off-by: Roger Quadros <rogerq@ti.com>
>> Acked-by: Peter Chen <peter.chen@nxp.com>
>> ---
>>
>> Changelog:
>> v2
>> - Add Fixes line
>>
>> drivers/usb/cdns3/gadget.c | 31 ++++++++++++++++++++++++++-----
>> 1 file changed, 26 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/usb/cdns3/gadget.c b/drivers/usb/cdns3/gadget.c
>> index 40dad4e8d0dc..1c724c20d468 100644
>> --- a/drivers/usb/cdns3/gadget.c
>> +++ b/drivers/usb/cdns3/gadget.c
>> @@ -2338,9 +2338,35 @@ static int cdns3_gadget_udc_start(struct usb_gadget *gadget,
>> {
>> struct cdns3_device *priv_dev = gadget_to_cdns3_device(gadget);
>> unsigned long flags;
>> + enum usb_device_speed max_speed = driver->max_speed;
>>
>> spin_lock_irqsave(&priv_dev->lock, flags);
>> priv_dev->gadget_driver = driver;
>> +
>> + /* limit speed if necessary */
>> + max_speed = min(driver->max_speed, gadget->max_speed);
>> +
>> + switch (max_speed) {
>> + case USB_SPEED_FULL:
>> + writel(USB_CONF_SFORCE_FS, &priv_dev->regs->usb_conf);
>> + writel(USB_CONF_USB3DIS, &priv_dev->regs->usb_conf);
>> + break;
>> + case USB_SPEED_HIGH:
>> + writel(USB_CONF_USB3DIS, &priv_dev->regs->usb_conf);
>> + break;
>> + case USB_SPEED_SUPER:
>> + break;
>> + default:
>> + dev_err(priv_dev->dev,
>> + "invalid maximum_speed parameter %d\n",
>> + max_speed);
>> + /* fall through */
>> + case USB_SPEED_UNKNOWN:
>> + /* default to superspeed */
>> + max_speed = USB_SPEED_SUPER;
>> + break;
>> + }
>
> I had suggested some simplification for this case statement.
>

oops, looks like Greg picked this already.

During more tests today I just observed that this patch causes
the following regression.

Connect EVM to Super-Speed host
Load g_audio. (this enumerates as HS which is fine)
unload g_audio
load g_zero (this enumerates at HS instead of SS).

This is because the speed limit that we set doesn't get cleared.

Now the bits are write only and there is a way to undo USB_CONF_SFORCE_FS
by writing USB_CONF_CFORCE_FS, however there is no corresponding bit
to clear USB_CONF_USB3DIS. Only way seems to be USB_CFG_SWRST which
is a bit harsh IMO.

Pawel,

could you please confirm what is the best way to undo the high-speed
limit?

--
cheers,
-roger
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
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