From:   Yaqin Pan <akingchen@vivo.com>
To:     gregkh@linuxfoundation.org
Cc:     akingchen@vivo.com, balbi@kernel.org, devicetree@vger.kernel.org,
        kernel@vivo.com, linux-kernel@vger.kernel.org,
        linux-usb@vger.kernel.org, robh+dt@kernel.org
Subject: Re: [PATCH v3 1/2] usb: dwc3: Add a quirk to set GUCTL.SPRSCTRLTRANSEN bit.
Date:   Fri, 31 Dec 2021 19:59:31 +0800
Message-Id: <20211231115931.20628-1-akingchen@vivo.com>
In-Reply-To: <Yc3UuSRkgiopJ5jp@kroah.com>
References: <Yc3UuSRkgiopJ5jp@kroah.com>
Precedence: bulk

On Thu, 30 Dec 2021 16:48:09 +0100 Greg Kroah-Hartman wrote:
>On Thu, Dec 30, 2021 at 11:36:12PM +0800, Yaqin Pan wrote:
>> On Thu, 30 Dec 2021 15:12:27 +0100 Greg Kroah-Hartman wrote:
>> >> This quirk is only for dwc3 host mode.
>> >> the dwc3 controller can't emurate some devices successfully.
>> >> For example, TF card reader (aaaa:8816):
>> >> failed log
>> >> usb 1-1: new high-speed USB device number 2 using xhci-hcd
>> >> usb 1-1: device descriptor read/all, error -110
>> >> >From the usb analyzer, always return NAK in the data phase.
>> >> if enable the GUCTL.SPRSCTRLTRANSEN bit. then the log is:
>> >> usb 2-1: new high-speed USB device number 3 using xhci-hcd
>> >> usb 2-1: New USB device found, idVendor=aaaa,
>> >> idProduct=8816, bcdDevice=13.08
>> >> usb 2-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
>> >> usb 2-1: Product: MXT USB Device
>> >> usb 2-1: Manufacturer: MXTronics
>> >> usb 2-1: SerialNumber: 150101v01
>> >> usb 2-1: New USB device found, VID=aaaa, PID=8816
>> >> 
>> >> Some devices are slow in responding to Control transfers.
>> >> Scheduling mulitiple transactions in one microframe/frame
>> >> can cause the devices to misbehave. if this qurik is enabled,
>> >> the host controller schedules transations for a Control transfer
>> >> in defferent microframes/frame.
>> >
>> >If this is needed for all devices (i.e. you do not know what device is
>> >going to be plugged in), why not just enable it for all controllers?
>> >Why whould you NOT want this enabled?
>> >
>> >Or is this a broken hardware device and only specific host controllers
>> >need this?  If so, how do we know which ones need this set and which do
>> >not?
>> 
>> I think not all dwc3 controllers need this. For cell phone,customers may
>> use various usb devices, we can enable this quirk to fix some compatibility
>> issues. For some chip platform of qcom, i encounter this issue, not every
>> platform i encounter this problem.
>> 
>> If enabled for all controllers, it will reduce the speed of Control transfers. 
>> So i think it would be better for user to enable it by their own purposes.
>
>But how do hardware vendors know to enable this?  Can we trigger off of
>PCI ids?  Do we need a list of quirks to show which host controllers are
>broken this way?
>
>Burying something as basic as "reliable device connection" in a DT quirk
>seems very sloppy to me.  We want reliable systems, right?

Yes, we want reliable systems. But i don't have a good ideal about this issue.
when we meet this problem, and from the dwc-usb3 controller datasheet,we know
enable one bit in dwc-usb3 controller's register can fixed this issue.

Of course, i can list the host controllers that i used broken this way if needed.

thanks,

Yaqin pan