Re: [PATCH] usb: dwc3: core: Do core softreset when switch mode

[Thinh Nguyen <Thinh.Nguyen@synopsys.com>]

Felipe Balbi wrote:
> 
> Hi,
> 
> Thinh Nguyen <Thinh.Nguyen@synopsys.com> writes:
>> From: Yu Chen <chenyu56@huawei.com>
>> From: John Stultz <john.stultz@linaro.org>
>>
>> According to the programming guide, to switch mode for DRD controller,
>> the driver needs to do the following.
>>
>> To switch from device to host:
>> 1. Reset controller with GCTL.CoreSoftReset
>> 2. Set GCTL.PrtCapDir(host mode)
>> 3. Reset the host with USBCMD.HCRESET
>> 4. Then follow up with the initializing host registers sequence
>>
>> To switch from host to device:
>> 1. Reset controller with GCTL.CoreSoftReset
>> 2. Set GCTL.PrtCapDir(device mode)
>> 3. Reset the device with DCTL.CSftRst
>> 4. Then follow up with the initializing registers sequence
>>
>> Currently we're missing step 1) to do GCTL.CoreSoftReset and step 3) of
> 
> we're not really missing, it was a deliberate choice :-) The only reason
> why we need the soft reset is because host and gadget registers map to
> the same physical space within dwc3 core. If we cache and restore the
> affected registers, we're good ;-)

It's part of the programming model. I've already discussed with internal
RTL designers. This is needed, and I've provided the discussion we had
prior also. We have several different devices in the wild that need
this. What is the concern?

> 
> IMHO, that's a better compromise than doing a full soft reset.
> 
>> @@ -40,6 +41,8 @@
>>  
>>  #define DWC3_DEFAULT_AUTOSUSPEND_DELAY	5000 /* ms */
>>  
>> +static DEFINE_MUTEX(mode_switch_lock);
> 
> there are several platforms which more than one DWC3 instance. Sure this
> won't break on such systems?
> 

How? Am I missing something? Please let me know so I can make the change.

Thanks,
Thinh