linux-kernel - Re: [PATCH v2] usb: dwc3: core: set force_gen1 bit in USB31 devices if max speed is SS

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Date:   Thu, 6 Jul 2023 19:18:53 +0530
From:   Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "quic_ppratap@...cinc.com" <quic_ppratap@...cinc.com>,
        "quic_wcheng@...cinc.com" <quic_wcheng@...cinc.com>,
        "quic_jackp@...cinc.com" <quic_jackp@...cinc.com>,
        "quic_ugoswami@...cinc.com" <quic_ugoswami@...cinc.com>
Subject: Re: [PATCH v2] usb: dwc3: core: set force_gen1 bit in USB31 devices
 if max speed is SS



On 5/17/2023 5:41 AM, Thinh Nguyen wrote:
> On Sun, May 14, 2023, Krishna Kurapati wrote:
>> Currently for dwc3_usb31 controller, if maximum_speed is limited to
>> super-speed in DT, then device mode is limited to SS, but host mode
>> still works in SSP.
>>
>> The documentation for max-speed property is as follows:
>>
>> "Tells USB controllers we want to work up to a certain speed.
>> Incase  this isn't passed via DT, USB controllers should default to
>> their maximum HW capability."
>>
>> It doesn't specify that the property is only for device mode.
>> There are cases where we need to limit the host's maximum speed to
>> SuperSpeed only. Use this property for host mode to contrain host's
>> speed to SuperSpeed.
>>
>> Signed-off-by: Krishna Kurapati <quic_kriskura@...cinc.com>
>> ---
>> Link to v1: https://urldefense.com/v3/__https://lore.kernel.org/all/20230512170107.18821-1-quic_kriskura@quicinc.com/__;!!A4F2R9G_pg!dCg_3WK2oNXNb6d0a_VuyjkeeZJTU1aY4dik6g35XB7mtG7EJeR1uPMfxFja49OfXp7Yhsg1yqjnylCYYEg7YCAhqfAZ0Q$
>>
>> Discussion regarding the same at:
>> https://urldefense.com/v3/__https://lore.kernel.org/all/e465c69c-3a9d-cbdb-d44e-96b99cfa1a92@quicinc.com/__;!!A4F2R9G_pg!dCg_3WK2oNXNb6d0a_VuyjkeeZJTU1aY4dik6g35XB7mtG7EJeR1uPMfxFja49OfXp7Yhsg1yqjnylCYYEg7YCDRLUrJWg$
>>
>>   drivers/usb/dwc3/core.c | 8 ++++++++
>>   drivers/usb/dwc3/core.h | 5 +++++
>>   2 files changed, 13 insertions(+)
>>
>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>> index 278cd1c33841..33bc72595e74 100644
>> --- a/drivers/usb/dwc3/core.c
>> +++ b/drivers/usb/dwc3/core.c
>> @@ -1262,6 +1262,14 @@ static int dwc3_core_init(struct dwc3 *dwc)
>>   		}
>>   	}
>>   
>> +	if ((hw_mode != DWC3_GHWPARAMS0_MODE_GADGET) &&
>> +	    (DWC3_IP_IS(DWC31)) &&
>> +	    (dwc->maximum_speed == USB_SPEED_SUPER)) {
>> +		reg = dwc3_readl(dwc->regs, DWC3_LLUCTL);
>> +		reg |= DWC3_LLUCTL_FORCE_GEN1;
>> +		dwc3_writel(dwc->regs, DWC3_LLUCTL, reg);
>> +	}
>> +
> 
> Perhaps this should be done for every usb3 port rather than just the
> port_0. This patch can go after your multi-port series is added to
> Greg's branch where you can check for number of usb3 ports.
> 
> Thanks,
> Thinh
> 

Hi Thinh,

   Seems like multiport would take little more time and I need this 
patch to be ported to ACK for fixing customer issue. Would it be 
possible to take this patch as is ? Once multiport is done, I will send 
another patch to include the changes for mutliport as well.

Regards,
Krishna,