linux-kernel - Re: [PATCH] Revert "usb: cdns3: core: quit if it uses role switch class"

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Date:   Tue, 24 Nov 2020 11:39:19 +0200
From:   Roger Quadros <rogerq@...com>
To:     Peter Chen <peter.chen@....com>
CC:     "pawell@...ence.com" <pawell@...ence.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "usb: cdns3: core: quit if it uses role switch
 class"

Peter,

On 24/11/2020 08:43, Peter Chen wrote:
> On 20-11-23 13:50:51, Roger Quadros wrote:
>> This reverts commit 50642709f6590fe40afa6d22c32f23f5b842aed5.
>>
>> This commit breaks hardware based role switching on TI platforms.
>> cdns->role_sw is always going to be non-zero as it is a pointer
>> to the usb_role_switch instance. Some other means needs to be used
>> if hardware based role switching is not required by the platform.
>>
>> Signed-off-by: Roger Quadros <rogerq@...com>
>> ---
>>   drivers/usb/cdns3/core.c | 4 ----
>>   1 file changed, 4 deletions(-)
>>
>> diff --git a/drivers/usb/cdns3/core.c b/drivers/usb/cdns3/core.c
>> index a0f73d4711ae..4c1445cf2ad0 100644
>> --- a/drivers/usb/cdns3/core.c
>> +++ b/drivers/usb/cdns3/core.c
>> @@ -280,10 +280,6 @@ int cdns3_hw_role_switch(struct cdns3 *cdns)
>>   	enum usb_role real_role, current_role;
>>   	int ret = 0;
>>   
>> -	/* Depends on role switch class */
>> -	if (cdns->role_sw)
>> -		return 0;
>> -
>>   	pm_runtime_get_sync(cdns->dev);
>>   
>>   	current_role = cdns->role;
>> -- 
> 
> Hi Roger,
> 
> I am sorry about that. Do you use role switch /sys entry, if you have
> used, I prefer using "usb-role-switch" property at dts to judge if
> SoC OTG signals or external signals for role switch. If you have not
> used it, I prefer only setting cdns->role_sw for role switch use cases.
> 

We use both hardware role switch and /sys entries for manually forcing
a certain role.

We do not set any "usb-role-switch" property at DTS.

Currently cdns->role_sw is being always set by driver irrespective of
any DT property, so this patch is clearly wrong and needs to be reverted.

What do you think?

cheers,
-roger
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