Re: [PATCH] usb: dwc3: Fix timeout issue during controller enter/exit from halt state

[Krishna Kurapati <krishna.kurapati@oss.qualcomm.com>]

On 2/1/2025 5:45 AM, Thinh Nguyen wrote:
> On Fri, Jan 31, 2025, Selvarasu Ganesan wrote:
>> There is a frequent timeout during controller enter/exit from halt state
>> after toggling the run_stop bit by SW. This timeout occurs when
>> performing frequent role switches between host and device, causing
>> device enumeration issues due to the timeout. This issue was not present
>> when USB2 suspend PHY was disabled by passing the SNPS quirks
>> (snps,dis_u2_susphy_quirk and snps,dis_enblslpm_quirk) from the DTS.
>> However, there is a requirement to enable USB2 suspend PHY by setting of
>> GUSB2PHYCFG.ENBLSLPM and GUSB2PHYCFG.SUSPHY bits when controller starts
>> in gadget or host mode results in the timeout issue.
>>
>> This commit addresses this timeout issue by ensuring that the bits
>> GUSB2PHYCFG.ENBLSLPM and GUSB2PHYCFG.SUSPHY are cleared before starting
>> the dwc3_gadget_run_stop sequence and restoring them after the
>> dwc3_gadget_run_stop sequence is completed.
>>
>> Fixes: 72246da40f37 ("usb: Introduce DesignWare USB3 DRD Driver")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Selvarasu Ganesan <selvarasu.g@samsung.com>
>> ---
>>   drivers/usb/dwc3/gadget.c | 21 +++++++++++++++++++++
>>   1 file changed, 21 insertions(+)
>>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index d27af65eb08a..4a158f703d64 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -2629,10 +2629,25 @@ static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on)
>>   {
>>   	u32			reg;
>>   	u32			timeout = 2000;
>> +	u32			saved_config = 0;
>>   
>>   	if (pm_runtime_suspended(dwc->dev))
>>   		return 0;
>>   
> 
> Can you add some comments here that this was added through experiment
> since it is not documented in the programming guide. It would be great
> to also note which platform you used to test this with.
> 

I did see this issue during pullup_exit() in SM6375 and SM8150 targets. 
The exact code logic worked out for me downstream.

Regards,
Krishna,