Re: USB 3.2 Gen 2x2 "Superspeed+20GBps" support for ASM3242

From: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
To: youling 257 <youling257@gmail.com>,
	Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
	"mathias.nyman@intel.com" <mathias.nyman@intel.com>,
	"william.allentx@gmail.com" <william.allentx@gmail.com>,
	"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Subject: Re: USB 3.2 Gen 2x2 "Superspeed+20GBps" support for ASM3242
Date: Fri, 31 Dec 2021 07:02:37 +0000	[thread overview]
Message-ID: <ae6d47c7-68f2-e482-c6ef-d2c63e2a9057@synopsys.com> (raw)
In-Reply-To: <CAOzgRdbgepUHKCmg8wR0s0bvYyuWNachi_EP6c9n_mRvQkXmGw@mail.gmail.com>

youling 257 wrote:
> 2021-12-31 11:46 GMT+08:00, Thinh Nguyen <Thinh.Nguyen@synopsys.com>:
>> Hi,
>>
>> youling 257 wrote:
>>> test this patch, cat /sys/bus/usb/devices/4-1/speed, 10000
>>> [   74.694284] usb 4-1: new SuperSpeed Plus Gen 2x1 USB device number
>>> 2 using xhci_hcd
>>> [   74.750329] usb-storage 4-1:1.0: USB Mass Storage device detected
>>>
>>> but speed, pcie to usb3.2 gen2x2, WRITE: bw=642MiB/s (673MB/s),
>>> 642MiB/s-642MiB/s (673MB/s-673MB/s), io=1000MiB (1049MB),
>>> run=1557-1557msec
>>> READ: bw=467MiB/s (490MB/s), 467MiB/s-467MiB/s (490MB/s-490MB/s),
>>> io=1000MiB (1049MB), run=2140-2140msec
>>>
>>> the mainboard usb3.2 gen2x1, WRITE: bw=838MiB/s (878MB/s),
>>> 838MiB/s-838MiB/s (878MB/s-878MB/s), io=1000MiB (1049MB),
>>> run=1194-1194msec
>>> READ: bw=753MiB/s (790MB/s), 753MiB/s-753MiB/s (790MB/s-790MB/s),
>>> io=1000MiB (1049MB), run=1328-1328msec
>>>
>>
>> Let's avoid top-post.
>>
>> Some comments:
>> 1) Just because the host is capable of gen2x2, it doesn't mean it will
>> run at gen2x2 speed. Your device can only operate up to gen2x1 speed, so
>> that's the limit. The test speed for gen2x1 above is not unreasonable.

> my device can only operate up to gen2x1 10gbps speed on window, only
> 5gbps on linux kernel 5.16rc7.

With the change I provided, you were able to run test at gen2x1, albeit
slower than expect. (i.e. write speed at 673MB/s for ASmedia host must
be SSP). The issue with device unable to operate at SSP is at least
answered.

If you're looking to find out why the performance is slow, confirm these
items first:

1) Are you using the same application to test on Linux to compare with
Windows? (Looks like you're using CrystalDiskMark for your Windows test)

2) If you're using the same application, are you using the same test
parameters and version?

3) Is your device operating in BOT or UASP in Linux? UAS Protocol is
generally faster. Newer device generally uses UASP, and I assume yours
is a newer device (check your enclosure). Make sure there's no quirk
preventing the device operating in UASP.

If all of those are checked out, you can start capturing logs so others
may look into it.

BR,
Thinh

(btw, I'll be on vacation for a week, maybe others can help while I'm away.)