Polling-Rate for USB-Touchpad?

Poison Nuke · 08-17-2018, 03:52 AM

Hello,

is there a way to set the polling rate for a touchpad?
Im using a Magic Trackpad 2 and Im receiving 90 updates per second from my customized kernel-module.

But bInterval in lsmod reports an poll-rate of 8ms, how is that possible? So it should update 125 times a second, not only 90.

Ive tried to set the mousepoll option in usbhid without effect.

It is a Raspbian with kernel 4.17.

ferrari · 08-17-2018, 04:16 PM

This Archwiki reference may be helpful here
https://wiki.archlinux.org/index.php/Mouse_polling_rate
In particular, this link to the section about polling rates not changing when plugged in to a USB3.0 port (with the xhci_hcd driver)...
https://wiki.archlinux.org/index.php...e_not_changing

Poison Nuke · 08-18-2018, 03:45 AM

thank you, but Ive tried that and some other mousepoll tutorials already, but didnt change anything.

I also wonder, why bInterval (and so evhz too) is reporting 8 ms, but still there are only 90 updates per second ?

ferrari · 08-18-2018, 03:52 AM

I was pointing you at a possible reason why the polling rate might not be work as expected. Is the the mouse connected to a USB 2.0 or USB 3.0 port? Is the xhci_hcd driver in use for that port?

Report back with the output of

Code:

sudo cat /sys/kernel/debug/usb/devices

or

Code:

usb-devices

Poison Nuke · 08-18-2018, 04:08 AM

can do this on monday. But it is a Raspberry Pi 3B+ so cant be a USB3 for sure

the driver in use is the bcm5974 (a USB driver), which I modified slightly to send the polled data to my application directly. The system is a raspbian with simple Xfce desktop so that the Xorg-Server will run the driver. So possibly I have to change something on the xorg settings?

ferrari · 08-18-2018, 04:12 AM

It's more about the Linux *-hcd driver in use than the port. Don't get confused between the kernel and Xorg (userspace) input drivers.

Poison Nuke · 08-18-2018, 07:09 AM

what drivers are possible and which one would be worse?
And if I have that "bad" driver, could I easily change some lines of code in the source and recompile it? I guess it would be a bad idea, because a lot of other devices might get screwed or so? ^^

ferrari · 08-18-2018, 04:01 PM

Stay with the line of investigation (as per post #2 and #4). The Archwiki reference mentions

Quote:

Polling rate not changing

The USB 3 driver xhci-hcd may be ignoring the usbhid mousepoll setting. See the linux-usb mailing list message and Bug.

The xhci-hcd module should respect the interval requested by the device, so check the documentation for the device for a hardware or firmware setting.

A work-around that may help is to connect the device to a port using a different driver.

Another work-around is to disable xHCI. There might be a BIOS setting for this or you can do so by blacklisting the xhci-hcd module. However, either way will cause any USB 3 ports to act as USB 2 as the kernel will use the ehci-hcd module instead.

When we know if that is impacting here, it is possible to force the use of the ehci-hcd driver.

The other aspect I'm now wondering about is setting the polling rate with respect to the bcm5974 driver. I assume that you followed advice relating to the usbhid driver, and that won't be relevant here AFAIU.

Poison Nuke · 08-20-2018, 09:04 AM

it looks like the usbhid driver:

Quote:

raspberrypi:~# cat /sys/kernel/debug/usb/devices

T: Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=480 MxCh= 1
B: Alloc=-45096/800 us (-5636%), #Int=-22555, #Iso= 0
D: Ver= 2.00 Cls=09(hub ) Sub=00 Prot=01 MxPS=64 #Cfgs= 1
P: Vendor=1d6b ProdID=0002 Rev= 4.14
S: Manufacturer=Linux 4.14.44-v7+ dwc_otg_hcd
S: Product=DWC OTG Controller
S: SerialNumber=3f980000.usb
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr= 0mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=00 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 4 Ivl=256ms

T: Bus=01 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 2 Spd=480 MxCh= 4
D: Ver= 2.00 Cls=09(hub ) Sub=00 Prot=02 MxPS=64 #Cfgs= 1
P: Vendor=0424 ProdID=2514 Rev= b.b3
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr= 2mA
I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=01 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 1 Ivl=256ms
I:* If#= 0 Alt= 1 #EPs= 1 Cls=09(hub ) Sub=00 Prot=02 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 1 Ivl=256ms

T: Bus=01 Lev=02 Prnt=02 Port=00 Cnt=01 Dev#= 3 Spd=480 MxCh= 3
D: Ver= 2.00 Cls=09(hub ) Sub=00 Prot=02 MxPS=64 #Cfgs= 1
P: Vendor=0424 ProdID=2514 Rev= b.b3
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr= 2mA
I: If#= 0 Alt= 0 #EPs= 1 Cls=09(hub ) Sub=00 Prot=01 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 1 Ivl=256ms
I:* If#= 0 Alt= 1 #EPs= 1 Cls=09(hub ) Sub=00 Prot=02 Driver=hub
E: Ad=81(I) Atr=03(Int.) MxPS= 1 Ivl=256ms

T: Bus=01 Lev=03 Prnt=03 Port=00 Cnt=01 Dev#= 6 Spd=480 MxCh= 0
D: Ver= 2.10 Cls=ff(vend.) Sub=00 Prot=ff MxPS=64 #Cfgs= 1
P: Vendor=0424 ProdID=7800 Rev= 3.00
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr= 2mA
I:* If#= 0 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=00 Prot=ff Driver=lan78xx
E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=02(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E: Ad=83(I) Atr=03(Int.) MxPS= 16 Ivl=1ms

T: Bus=01 Lev=03 Prnt=03 Port=01 Cnt=02 Dev#= 4 Spd=12 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=05ac ProdID=0265 Rev= 8.04
S: Manufacturer=Apple Inc.
S: Product=Magic Trackpad 2
S: SerialNumber=CC2643204KCGTFQAA
C:* #Ifs= 4 Cfg#= 1 Atr=a0 MxPwr=500mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=00 Prot=00 Driver=usbhid
E: Ad=81(I) Atr=03(Int.) MxPS= 16 Ivl=8ms
I:* If#= 1 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=01 Prot=02 Driver=bcm5974
E: Ad=83(I) Atr=03(Int.) MxPS= 64 Ivl=1ms
I:* If#= 2 Alt= 0 #EPs= 2 Cls=03(HID ) Sub=00 Prot=00 Driver=usbhid
E: Ad=84(I) Atr=03(Int.) MxPS= 16 Ivl=8ms
E: Ad=04(O) Atr=03(Int.) MxPS= 64 Ivl=2ms
I:* If#= 3 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=00 Prot=00 Driver=usbhid
E: Ad=85(I) Atr=03(Int.) MxPS= 64 Ivl=2ms

T: Bus=01 Lev=03 Prnt=03 Port=02 Cnt=03 Dev#= 5 Spd=12 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=24ae ProdID=1006 Rev= 1.10
S: Manufacturer=RAPOO
S: Product=Rapoo 2.4G Wireless Touchpad Keyboard
C:* #Ifs= 3 Cfg#= 1 Atr=a0 MxPwr=100mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=01 Prot=02 Driver=usbhid
E: Ad=81(I) Atr=03(Int.) MxPS= 64 Ivl=10ms
I:* If#= 1 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=01 Prot=01 Driver=usbhid
E: Ad=82(I) Atr=03(Int.) MxPS= 64 Ivl=10ms
I:* If#= 2 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=01 Prot=01 Driver=usbhid
E: Ad=83(I) Atr=03(Int.) MxPS= 64 Ivl=10ms

So in theory, my settings should have an effect and poll the device with 125Hz and not 90?

ferrari · 08-20-2018, 02:38 PM

That looks as it should be. It is a composite USB device.

Code:

T: Bus=01 Lev=03 Prnt=03 Port=01 Cnt=02 Dev#= 4 Spd=12 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=05ac ProdID=0265 Rev= 8.04
S: Manufacturer=Apple Inc.
S: Product=Magic Trackpad 2
S: SerialNumber=CC2643204KCGTFQAA
C:* #Ifs= 4 Cfg#= 1 Atr=a0 MxPwr=500mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=00 Prot=00 Driver=usbhid
E: Ad=81(I) Atr=03(Int.) MxPS= 16 Ivl=8ms
I:* If#= 1 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=01 Prot=02 Driver=bcm5974
E: Ad=83(I) Atr=03(Int.) MxPS= 64 Ivl=1ms
I:* If#= 2 Alt= 0 #EPs= 2 Cls=03(HID ) Sub=00 Prot=00 Driver=usbhid
E: Ad=84(I) Atr=03(Int.) MxPS= 16 Ivl=8ms
E: Ad=04(O) Atr=03(Int.) MxPS= 64 Ivl=2ms
I:* If#= 3 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=00 Prot=00 Driver=usbhid
E: Ad=85(I) Atr=03(Int.) MxPS= 64 Ivl=2ms

The 'Spd=12' paramter shows that it is behaving as a 'full-speed' (USB 1.1) device, rather than a 'high-speed' (USB 2.0) device. Although these HID devices don't require high data rates (so full-speed is more than sufficient), I'm not sure if this might impact on the maximum polling rate somehow.

ferrari · 08-20-2018, 02:38 PM

That looks as it should be. It is a composite USB device.

Code:

T: Bus=01 Lev=03 Prnt=03 Port=01 Cnt=02 Dev#= 4 Spd=12 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=05ac ProdID=0265 Rev= 8.04
S: Manufacturer=Apple Inc.
S: Product=Magic Trackpad 2
S: SerialNumber=CC2643204KCGTFQAA
C:* #Ifs= 4 Cfg#= 1 Atr=a0 MxPwr=500mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=00 Prot=00 Driver=usbhid
E: Ad=81(I) Atr=03(Int.) MxPS= 16 Ivl=8ms
I:* If#= 1 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=01 Prot=02 Driver=bcm5974
E: Ad=83(I) Atr=03(Int.) MxPS= 64 Ivl=1ms
I:* If#= 2 Alt= 0 #EPs= 2 Cls=03(HID ) Sub=00 Prot=00 Driver=usbhid
E: Ad=84(I) Atr=03(Int.) MxPS= 16 Ivl=8ms
E: Ad=04(O) Atr=03(Int.) MxPS= 64 Ivl=2ms
I:* If#= 3 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=00 Prot=00 Driver=usbhid
E: Ad=85(I) Atr=03(Int.) MxPS= 64 Ivl=2ms

The 'Spd=12' paramter shows that it is behaving as a 'full-speed' (USB 1.1) device, rather than a 'high-speed' (USB 2.0) device. Although these HID devices don't require high data rates (so full-speed is more than sufficient), I'm not sure if this might impact on the maximum polling rate somehow.

Poison Nuke · 08-21-2018, 02:32 AM

but there stands lvl=8ms, that should be 125Hz, shouldnt it? So where does the 90Hz come from?

And for the bcm driver there is even a 1ms lvl listed, what does that mean?

ferrari · 08-21-2018, 03:03 AM

Quote:

So where does the 90Hz come from?

I'm not sure to be honest. Where did you see that reported?

Quote:

And for the bcm driver there is even a 1ms lvl listed, what does that mean?

Well, that implies a respectable 1000Hz polling rate.

Is your 'Magic Trackpad 2' responding as you'd like from an operational perspective? Maybe noting needs to be done explicitly.

Poison Nuke · 08-21-2018, 10:06 AM

I see the update rate in my application, which is fed directly from the bcm driver.

And Im creating a new input prototype and goal is less then 40ms total in out latency. At the moment I have 80ms, which is too much (you can feel it). So I try to minimize every possible bottleneck.

Synesthesia · 07-06-2019, 03:37 PM

How did this turn out? I'm curious about increasing the polling rate for the trackpad 2... I wonder if we can get it up to 500hz at least.